Global Crop Distribution: A Geographic Analysis

GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 18, GB1009, doi:10.1029/2003GB002108, 2004
Geographic distribution of major crops
across the world
Billie Leff,1 Navin Ramankutty, and Jonathan A. Foley
Center for Sustainability and the Global Environment (SAGE), Gaylord Nelson Institute for Environmental Studies,
University of Wisconsin, Madison, Wisconsin, USA
Received 6 June 2003; revised 8 October 2003; accepted 30 October 2003; published 16 January 2004.
[1] Humans have transformed the surface of the planet through agricultural activities, and
today, 12% of the land surface is used for cultivation and another 22% is used for pastures
and rangelands. In this paper, we have synthesized satellite-derived land cover data and
agricultural census data to produce global data sets of the distribution of 18 major crops
across the world. The resulting data are representative of the early 1990s, have a spatial
resolution of 5 min. (10 km), and describe the fraction of a grid cell occupied by each of
the 18 crops. The global crop data are consistent with our knowledge of agricultural
geography, and compares favorably to another existing data set that partially overlaps with
our product. We have also analyzed how different crops are grown in combination to form
major crop belts throughout the world. Further, we analyzed the patterns of crop
diversification across the world. While these data are not sufficiently accurate at local scales,
they can be used to analyze crop geography in a regional-to-global context. They can also
be used to understand the global patterns of farming systems, in analyses of food security,
and within global ecosystem and climate models to understand the environmental
INDEX TERMS: 1699 Global Change: General or miscellaneous; 1640
consequences of cultivation.
Global Change: Remote sensing; 1630 Global Change: Impact phenomena; 1694 Global Change: Instruments
and techniques; KEYWORDS: land use, land cover, croplands, crop distribution, agricultural census, crop
harvested area
Citation: Leff, B., N. Ramankutty, and J. A. Foley (2004), Geographic distribution of major crops across the world, Global
Biogeochem. Cycles, 18, GB1009, doi:10.1029/2003GB002108.
1. Introduction
[2] Humans dominate the landscape in nearly every corner
of the planet. Today, croplands occupy nearly 18 million
km2 (an area roughly the size of South America), pastures
take up another 34 million km2 (an area roughly the size
of Africa), and urban areas use roughly 2.5 million km2
(an area roughly the size of a third of Europe) [Klein
Goldewijk, 2001; Ramankutty and Foley, 1998; Turner et
al., 1993]. Altogether, these three anthropogenic ecosystems
currently occupy over a third of the global land surface.
[3] Human land use practices have enormous consequences
for the environment. While croplands and pastures provide
food for the world’s population, agricultural practices
have, to a large degree, led to the clearing of many forests
[Goudie, 2000]. Human land use practices have also degraded
many soils [Meyer and Turner, 1994], influenced global
and regional climates [Betts, 1999; Bounoua et al., 2002;
Brovkin et al., 1999; Pielke et al., 2002; Zhao and Pitman,
2002], changed the global cycles of carbon, nitrogen, and
water [Houghton et al., 1999; Vitousek et al., 1997; Postel
1
Now at National Geographic Maps, Washington, DC, USA.
Copyright 2004 by the American Geophysical Union.
0886-6236/04/2003GB002108
et al., 1996], induced the loss of biodiversity [Dale et al.,
2000; Pearce, 2001; McNeely, 1992], affected geomorphic
processes, and changed the quality of many natural waterways
[Goudie, 2000].
[4] Characterizing the geographic extent and nature of
human-dominated ecosystems is vital to understanding the
environmental impacts of land use and land cover change.
With the advent of remote sensing, there have been several
efforts aimed at depicting regional and global patterns of
land cover [Vogelmann et al., 2001; Cihlar, 2000; DeFries
and Belward, 2000; Belward et al., 1999; Lobo et al., 1997;
Brown et al., 1993; Loveland et al., 1991]. However, these
studies have mainly focused on natural ecosystems, with
only one or two land cover classes devoted to humandominated ecosystems. On the other hand, ground-based
census data (routinely collected across counties, states, and
nations) often contain detailed land use information, but
lack the spatial detail and resolution of satellite-based data.
[5] In order to characterize global agricultural land cover,
Ramankutty and Foley [1998] developed a statistical ‘‘data
fusion’’ technique to calibrate satellite-derived land cover
data [Loveland and Belward, 1997] against agricultural
census statistics. Their data represent the cropland land cover
of the world on a continuous scale, depicting the percentage
of each grid cell in cultivation (Figure 1). However, this data
set is still limited in not delineating the distribution of
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Figure 1. Global cropland data set of Ramankutty and Foley [1998]. This data set was created by
merging satellite-derived land cover data and administrative unit level agricultural census data. It
represents the fraction of a 5-min resolution (in latitude by longitude) grid cell occupied by arable lands
and permanent crops in 1992. See color version of this figure at back of this issue.
specific crop types and cropping systems. Detailed information on agricultural land use practices (such as cropping
systems) is necessary to understand the environmental
consequences of cultivated ecosystems. For example, the
distinction between C3- and C4-based physiology crops is
important in studies of the global carbon cycle [Lloyd and
Farquhar, 1994; Still et al., 2003]. In addition, Donner and
Kucharik [2003] discuss the importance of differentiating
between maize and soybeans on nitrate export through the
Mississippi River, and the spatial pattern of rice paddy is
important to estimate the distribution of methane emissions
[Cao et al., 1996; Matthews and Fung, 1987]. Moreover,
model-based estimates of historical and current crop
production [Kucharik, 2003] and future crop production
[Leemans and Solomon, 1994; Fischer et al., 2000] have
made distinctions between different crops.
[ 6 ] Here we use an approach, similar to that of
Ramankutty and Foley [1998], wherein we combine national and sub-national agricultural census data, along with land
cover data, to derive the spatial distribution of crop types
across the world. Our focus is also on cultivation within
permanent croplands, which follows the Food and Agriculture Organization (FAO) definition of arable lands and lands
under permanent crops (Table 1). Other land use systems,
including pastures and regions of shifting cultivation, are
not considered in this study.
2. Methods
[7] We derived the global distribution of 18 major crop
types by synthesizing agricultural census data on harvested
area, and the global cropland data set of Ramankutty and
Foley [1998]. The crop categories were selected using
distinct biogeochemical, phonological, and food resource
characteristics. We arrived at 17 major crop categories
(barley, cassava, cotton, groundnuts or peanuts, maize,
millet, oil palm fruit, potatoes, rapeseed or canola, rice,
rye, sorghum, soybeans, sugar cane, sugar beets, sunflower,
Table 1. A Glossary of Terms Used in This Paper
Term
Cropland
Major crops
Cropland area
Cropland fraction
Crop area
Crop fraction
Relative crop fraction
Cultivation intensity
Region
Description
Arable land (including harvested cropland, crop failure, temporarily fallow or idle land, and cropland used temporarily
for pasture) and land under permanent crops (such as cocoa, coffee, rubber, etc., including all tree crops except those
grown for wood or timber). The harvested produce may be used for both human consumption and/or feed.
One or more of the following: barley, cassava, cotton, groundnuts or peanuts, maize, millet, oil palm fruit, potatoes,
pulses, rapeseed or canola, rice, rye, sorghum, soybeans, sugar cane, sugar beets, sunflower, and wheat.
The area of each grid cell (in square kilometers) occupied by croplands.
The fraction of each grid cell occupied by croplands.
The area of each grid cell (in square kilometers) in any one of the major crops.
The fraction of each grid cell that is in any one of the major crops.
The ratio of harvested area of each crop to total harvested area.
In this paper, intensity refers to the magnitude of the crop fraction, i.e., the higher the crop fraction in a grid cell,
the greater its intensity of cultivation with respect to that particular crop. It does not refer to the land inputs such as
irrigation, fertilization, multiple cropping, etc.
An area in the world generally larger than a single country, but smaller than a continent (e.g., the Middle East, the
conterminous United States). The area of our regions ranges from just over 200,000 km2 (the Caribbean) to
14,000,000 km2 (Northern South America). See Table 5 for a list of the regions discussed here.
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RAMANKUTTY ET AL.: GLOBAL CROP DISTRIBUTION
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Table 2. Crop Commodity Classifications and Definitions [FAO, 2002]
Category
Cereals
barley
maize
millet
rice
rye
sorghum
wheat
Pulses
other cerealsb
cassava
potatoes
other root/tuberb
sugar beets
sugar cane
pulses
Nuts
nutsb
Oil-bearing crops
groundnuts
rapeseed
oil palm fruit
soybeans
sunflower
other oil-bearing cropsb
Vegetables
vegetablesb
Fruit
fruitb
Fibers
cotton
other fibersb
Spices
spicesb
Other crops
other cropsb
Roots and tubers
Sugar crops
FAO Crop Definition and Commentsa
Crop
Hordeum spp. Varieties include with husk and without (naked).
Zea mays. Includes hybrid and ordinary maize (with widely different yields).
Echinocloa frumentacea, Eleusine coracana, Eragrostis abyssinica, Panicum miliaceum,
Paspalum scrobiculatum, Pennisetum glaucum, Setaria italica. Small-grained cereals
that include a large number of different botanical species.
Oryza spp. Mainly oryza sativa. Rice grain after threshing and winnowing. Also known
as rice in the husk and rough rice.
Secale cereale.
Sorghum spp. Includes hybrid and other varieties.
Triticum spp. (T. durum and T. aestivum). Includes durum and common wheat, the latter
includes the varieties: spring, winter, hard, soft, red, and white.
Includes: oats, buckwheat, quinoa, fonio, triticale, canary seed, mixed grains.
Manihot spp. Other names: manioc, mandioca, yucca, yucca dulce.
Solanum tuberosum.
Includes: sweet potatoes, yautia, taro, and yams.
Beta vulgaris var. altissima.
Saccharum officinarum.
Includes: dry beans, dry broad beans, dry peas, chick-peas, dry cow peas, pigeon peas,
lentils, bambara beans, vetches, and lupins.
Includes: Brazil nuts, cashew nuts, chestnuts, almonds, walnuts, pistachios, kola nuts,
hazelnuts (filberts), and areca nuts.
Arachis hypogaea. Other name: peanuts.
Brassica napus var. oleifera. Other name: Canola.
Elaeis guineensis.
Glycine soja.
Helianthus annuus.
Includes: coconuts, olives, karate nuts, castor beans, tung nuts, safflower, sesame, mustard,
poppy seed, melon seed, linseed, hempseed, tallow tree seeds, kapok fruit, seed cotton.
Includes: cabbage, artichokes, asparagus, lettuce, spinach, cassava leaves, tomatoes,
cauliflower, pumpkins, cucumbers and gherkins, eggplants, chilies and peppers, onions,
garlic, leeks and other alliaceous vegetables, green beans, green peas, green broad beans,
string beans, carrots, okra, green corn, mushrooms, watermelons, and cantaloupes.
Includes: bananas, plantains, oranges, tangerines, mandarins, clementines, satsumas, lemons,
limes, grapefruit, pomelo, apples, pears, quinces, apricots, sour cherries, peaches,
nectarines, plums, stone fruit, strawberries, raspberries, gooseberries, currants, blueberries,
cranberries, grapes, figs, persimmons, kiwi fruit, mangoes, avocadoes, pineapple, dates,
cashew apple, and papayas.
Gossypium spp.
Includes: flax fiber and tow, hemp fiber and tow, kapok fiber, jute-like fibers, ramie, sisal,
abaca, manila hemp, and coir.
Includes: pepper, pimento, vanilla, cinnamon (or canela), nutmeg, mace, cardamoms, cloves,
anise, badian, fennel, and ginger.
Includes: tea, coffee, cocoa, mate, tobacco, natural rubber, chicory roots, carobs, hops,
peppermint and spearmint, pyrethrum, Arabic gum, and other resins.
a
For more detailed crop definitions, classifications and recommendations, visit the FAO Statistics Division web site at http://www.fao.org./es/ess/
rmcrops.asp.
b
Denotes a crop considered minor in this paper and one for which a separate data set was not generated, although census data, at least at the national
level, were available for all crops listed here.
and wheat), one major crop group category (pulses, which
includes many beans, peas, lentils, etc.), and 10 other
‘‘minor’’ crop categories (fibers, fruit, nuts, oil-bearing
crops, other cereals, other roots and tubers, others, spices,
and vegetables) (Table 2). Agricultural census data were
collected and regrouped into those categories and data sets
were generated for all eighteen major crops, while all other
crops and crop categories were grouped into a single ‘‘other
crop’’ category (Table 2).
[8] We collected agricultural census data from various
census organizations (Table 3). At the national level, agricultural census data are available for every country in the
world from the FAO in the FAOSTAT database [FAO,
2002]. This database contains harvested area data for over
100 individual crops, collected and reported annually for the
time period 1961 – 2001. In addition, to achieve some level
of uniformity in the size of administrative units, we collected
sub-national (one administrative level below the nation:
state or province equivalent) census data for a number of
countries, based on either their land area or their share
of global cropland area. These countries were Argentina,
Australia, Brazil, Canada, China, India, Kazakhstan,
Mexico, the Russian Federation, Turkey, and the United
States of America (Figure 2).
[9] We collected and averaged the census data for 6 years,
1990– 1995. This period centers roughly around 1992, the
year for which Ramankutty and Foley [1998] developed
their cropland distribution data set. Often the national totals
obtained from the sub-national censuses did not match the
FAO national data. After checking for consistency in definitions and for errors, we scaled all sub-national data to the
FAO national totals. Similarly, scaling was done in cases
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RAMANKUTTY ET AL.: GLOBAL CROP DISTRIBUTION
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Table 3. Agricultural Census Data Sources for 1990 – 1995, Inclusivelya
Location
Data Source
Comments
Countries of the world
Food and Agriculture Organization [2002]
States of Argentina
Instituto Nacional de Estadistica y Censos
[1995, 1996a, 1996b, 1996c]
States and Territories of Australia
Australian Bureau of Statistics [1991, 1992, 1994]
States of Brazil
Instituto Brasileiro de Geografia e Estatı́stica,
SIDRA: Banco de Dados Agregados, 1996
(available from the IBGE web site at
http://www.ibge.gov.br)
Statistics Canada [1992, 1997a, 1997b]
Provinces of Canada
Provinces of China
States of India
Oblasts of Kazakhstan
States of Mexico
Oblasts of the Russian Federation
State Statistical Bureau, PRC [1991 – 1996]
and U.S. Department of Agriculture [1999]
Ministry of Agriculture [1993]
Gosudarstveni Committet Kazahskoi
SSR po Statistike [1987]
Centro de Estadı́stica Agropecuaria [2000]
Goskomstat Rusii [1995] and
U.S. Department of Agriculture [1999]
Regions in Turkey
State Institute of Statistics [1994, 1995]
States of the United States of America
U.S. Department of Agriculture [2001]
We selected 18 major crops and averaged the
FAO harvested area data for those crops for
1990 – 1995 inclusively.
Census data were available only for the five
provinces in the Pampa for the calendar years
1993 – 1995 inclusively. No data were
available on cotton.
Data collected for 1990 – 1994 inclusively. For
rapeseed/canola, data were available only for 1990.
Only a single census for 1996 was available.
Agricultural censuses were available for 1991
and 1996 only. The pulse category was limited
to dry peas and beans and no data were available
for other pulses.
Census data were available for every year between
1990 and 1995 inclusively.
Data were available for three crop years 1990 – 1991,
1991 – 1992, and 1992 – 1993.
Census data were available only for 1986. No data
were available on barley.
Data were available only for 1991.
Census data were available for 1990 – 1995 inclusively
for most crops. Barley data were available only by
regions (group of oblasts) for 1968 – 1970. For rye,
only data on production (tons) were available.
Data were available for 1991 and 1993, and it was
by region rather than by state. There were 9
regions with 5 to 11 states each.
Data were available for 1990 – 1995 inclusively for
all crops, except for millet, for which only 1987
data were found.
a
We collected agricultural census data for all administrative units for the years 1990 through 1995 inclusively, unless otherwise noted in the comments.
where sub-national data were not available for all six years
(see Appendix A).
[10] The census data for each crop were converted to a
relative crop fraction (the proportion of a particular crop’s
harvested area to the total harvested area) (see Table 1 for
definition of terms used in this paper). This fraction was
assigned to the administrative unit for which it was obtained
(Figure 3). It should be noted that the harvested area data for
Figure 2. Countries of the world for which agricultural census data were collected. For the countries in
white, only national-level census data were collected from the FAO [2002], while for the countries in
black (nations with large total cultivated area or total land area), we collected state-level data (see Table 3
for agricultural census data sources).
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RAMANKUTTY ET AL.: GLOBAL CROP DISTRIBUTION
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Figure 3. Flowchart showing the methodology used to construct the major crop data sets. Boxes with
rounded corners indicate geospatial data sets, while boxes with sharp corners indicate tabular data at the
level of political units. We first collected agricultural census data on harvested area for crops at the
national or sub-national level. From these data, for each administrative unit, we then estimated
the proportion of each of the 18 major crops to the total harvested area. We then masked non-cropland
areas and applied a smoothing algorithm (see text for details). Finally, we multiplied the resulting data of
individual crop proportions by the cropland data set (Figure 1) to obtain the per-pixel proportion of each
of the 18 major crops.
all crops do not directly sum up to reported cropland area.
This is because of multiple cropping (the practice where the
same land is cultivated 2 or even 3 times throughout the
same year). Here we assumed that all crops within a region
have similar multiple cropping patterns. Thus, by expressing the harvested area for each crop as a proportion of the
total, we obtained for every pixel the probability that a
particular crop is cultivated.
[11] Next we used the data set of the extent of the world’s
croplands [Ramankutty and Foley, 1998] to mask out noncropland areas. Then we smoothed the data to eliminate
discontinuities at the borders between political units.
Although real crop discontinuities exist between some
nations, all of the boundaries we have introduced are
artificial and arise solely because of our use of administrative level data. Hence we smoothed these by applying a
41 41 pixel Gaussian filter. Since the smoothing may
have introduced biases in the data, we rescaled the data
equally for all crops to ensure that all fractions indeed added
to 1. This smoothing and normalization significantly altered
the census data in administrative units where both of the
following conditions are met: the unit has a width in any
direction smaller than the width of the filter, and the unit has
a crop proportion significantly different from that of the
surrounding administrative units.
[12] Finally, to obtain the spatial distribution of each crop
(fraction of grid cell occupied by the crop, what we define
as ‘‘crop fraction’’), we multiplied the spatially distributed
relative crop fraction from the previous step by the cropland
data set of Ramankutty and Foley [1998]. The 18 crop data
sets thus produced are gridded, global, and at a 5-min
latitude/longitude resolution (10 km) (Figures 4a – 4f).
[13] These crop data have been created using a very simple
procedure (Figure 3), with multiple assumptions, and thus
have several limitations. First, the use of national and state
level data, without the ability to define cultivation intensities
within administrative units, makes the data appropriate only
for regional- to global-scale studies. Secondly, in regions
where some crops have multiple growing seasons and others
have single growing seasons, the assumption of the same
number of growing seasons will lead to overestimation of the
extent of the former (e.g., rice and pulses), and underestimation of the extent of the latter (e.g., millet, wheat, and
barley). This is the case especially in the tropics where
certain crops are planted and harvested multiple times, while
others are not. Third, reporting errors in the census data
may considerably alter the final results. This is especially
true for countries where there may be political or economic
incentives to over- or under-report cropland area (e.g., China
[see Seto et al., 2000]). Fourth, the effects of the smoothing
filter are difficult to quantify. Most frequently the affected
areas are along the border between administrative units,
across which cultivation intensities vary greatly because of
cultural or environmental differences: small states and
countries surrounded by larger administrative units, and
long and narrow administrative units. Finally, errors in the
Ramankutty and Foley [1998] croplands data set would carry
over to these new data sets.
[14] Despite the simplicity of the approach used to generate these data, they are the first of their kind. By merging
the high spatial resolution of satellite-derived data and the
high level of attribute differentiation in census data, these
data represent a useful product to be used within numerical
models (of the Earth’s climate, terrestrial ecosystems, and
hydrological systems) and by land managers, planners, and
policy makers.
[15] One caveat to add is that the data, in their current
form, do not identify some important phenological charac-
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RAMANKUTTY ET AL.: GLOBAL CROP DISTRIBUTION
teristics of crops such as spring crops versus winter crops.
Such distinctions are very important when assessing the
environmental consequences of crops. We recommend that
climate and ecosystem modelers use climate data in conjunction with our crop data sets to distinguish between the
different crop phenologies [e.g., Leemans and Solomon,
1993]. In future updates of this product, we plan to
incorporate these distinctions.
3. Data Evaluation
[16] Although the geographic distribution of total croplands has been mapped on a global scale [Ramankutty and
Foley, 1998; Wood et al., 2000], there are no independent
geospatial data sets for the global distribution of the world’s
major crops. This makes our effort unique, but also presents
us with the challenge of performing a comprehensive
quality assessment without comparable data.
[17] To our knowledge, there have been three other efforts
that have attempted to characterize the spatial distribution of
crops on a global scale. The FAO, in collaboration with the
International Institute for Applied Systems Analysis
(IIASA), estimated the global land suitability for growing
different crops [Fischer, 2000]. Although valuable, this
product only indicates where crops could be grown, and
is not a representation of where crops are grown today.
Another effort by the National Institute for Public Health
and the Environment (RIVM) in the Netherlands spatially
allocated the FAO national agricultural census data into
pixels by using a measure of land suitability for seven
different aggregate crops [IMAGE-team, 2001]. Once again,
while this is a useful product, it is not strictly comparable to
ours because it reflects land suitability rather than actual
cultivated areas, and also is based on data for the year 1970.
Indeed, a quantitative comparison of the RIVM data set to
our product showed that the two data sources have poor
correspondence: the correlation coefficient ranged from a
low of 38% (for soybeans) to 57% (for rice).
[18] The only product comparable to ours can be found in
a recent publication by the Joint Agricultural Weather
Facility (JAWF) of the U.S. Department of Agriculture
(USDA) [USDA/JAWF, 1994] (also available at http://
www.usda.gov/oce/waob/jawf/profiles/mwcacp.htm), where
they presented the major crop growing regions of the world.
However, the product is not digital or geospatially
referenced, and we are thus limited to a qualitative comparison. The USDA/JAWF publication allows us to compare the global distributions of all but four (potatoes,
cassava, pulses, and oil palm fruit) of the 18 major crops.
Rather than presenting cultivation intensity per pixel, the
USDA/JAWF data set delineates two levels of cultivation in
each region: ‘‘major’’ and ‘‘minor.’’ While the publication
does not cover the whole world, it is valuable in providing
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climatological and crop calendar data for the world’s major
crop growing areas.
[19] Despite the different format and source materials, our
data agree with the USDA publication on the distribution of
a large number of the major crops throughout the world.
However, there are also a significant number of crop
growing areas in which the two data sets differ. In Table 4,
we present the areas of agreement and disagreement, as well
as those areas for which a comparison is not available
because of the non-global nature of the USDA data. In
most cases where the two data sets compare poorly, it is
because of the lack of sub-national or sub-state level census
data in our data sets. This is the case with the cultivation of
crops in large administrative areas (e.g., the Canadian
Prairie Provinces, the Australian states, Mongolia, Pakistan,
Nigeria, France, Spain, Germany, and Poland) and with
crops having narrow growing areas (e.g., cotton, sugar cane,
rapeseed, and canola). In other cases, the two data sources
differ even where census data are available with the same
resolution (e.g., the cultivation of maize throughout
Mexico). This might be related to inaccuracies in the
Ramankutty and Foley [1998] croplands data set that forms
the basis of our major crop data sets.
4. Global Cropping Patterns
[20] Here we discuss the global distribution of major crop
groups (Figures 4a – 4f, 5, and 6).
4.1. Cereals
[21] The most prevalent group of crops across the world is
cereals (Figures 4a – 4c). Taken together, cereals are the only
group of crops with cultivation that exceeds 20% of global
land area (Figures 5a – 5c), or 61% of the total cultivated
land. In particular, wheat, maize, barley, rice, and millet are
dominant over more than two thirds of the cropland of the
world (Table 5). The only regions where a cereal is not
the dominant crop are the Caribbean and central Africa. In
the Caribbean, the dominant major crop is sugar cane; while
in central Africa, the dominant major crop is cassava.
However, in both regions, a cereal (maize) is the second
most prevalent crop (Tables 6 and 7).
[22] A breakdown by latitude also reveals the dominance
of cereals (Figures 5a – 5c). Wheat is the most abundant
crop, occupying 22% of the total cultivated area in the
world. The most intensive wheat cultivation occurs in the
temperate latitudes of both hemispheres. Wheat is most
prevalent in the Great Plains of the United States, the
Canadian Prairie Provinces, the Indus and the upper Ganges
Valleys, along the Kazakhstan and Russian border, and in
southern Australia (Figure 4c). Wheat is also found
throughout Europe, in southern South America, in parts of
eastern Africa, and in eastern China.
Figure 4. Global distribution of 18 major crops. The 18 major crops were selected based on biogeochemical,
phenological, and food resource characteristics. We first display seven cereals (barley, maize, millet, rice, rye, sorghum, and
wheat), then two tubers (cassava and potatoes), two sugar crops (sugar beets and sugar cane), a single category for pulses,
five oil-bearing crops (soybeans, groundnuts or peanuts, rapeseed or canola, sunflower, and oil palm fruit), and finally, a
single crop for the fiber category (cotton). Note that a very compressed scale is chosen to better display the data in gray
scale, although the data have continuous values from 0 to 100%.
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Figure 4. (continued)
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Figure 4. (continued)
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Figure 4. (continued)
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Figure 4. (continued)
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Figure 4. (continued)
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Table 4. Qualitative Comparison of the Data From USDA/JAWF, 1994 and This Study
Crop
Wheat
Areas of Agreement
Areas of Disagreement
Major Cultivation Zones
Without USDA Data
Rice
USDA major growing areas in
USDA minor growing areas in the
North America and Europe (France, UK,
USA and Canada (Saskatchewan);
Italy, Romania, and Poland); all
Pakistan, South Africa, parts of Europe
cultivation in South America, Russia,
(Spain and Germany); USDA major
Kazakhstan, Northern Africa, India,
growing areas in China
and Australia
USA, Brazil, and Southeast Asia
Maize
USA, Europe, India, and China
Mexico, Brazil, Argentina
Barley
Sorghum
Millet
Rye
Sugar cane
Belarus and Russia, northwestern Africa
Mexico, India
India
Former Soviet Union
southeastern USA, Cuba, Brazil,
India, and China
Sugar beets
Cotton
China
South America, former Soviet Union,
Pakistan, and China
USA, Canada, Brazil, India, and China
North America and Europe (UK and Spain)
USA, Argentina, and Australia
China, Africa
Russia, China, Africa
Europe (Germany and Poland)
Queensland in Australia, India, Pakistan,
Central America and the Caribbean
Philippines, and South Africa
(other than Cuba), South America,
central Africa
USA, Europe, and Kazakhstan
Chile and Turkey
USA, Argentina, Spain, Egypt,
Africa, Peru, Turkey, Afghanistan,
Australia, and India
and Thailand
Italy, India, and Argentina
Southeast Asia (other than
India and China)
southeastern USA
Africa and Southeast Asia
(other than India and China)
Canadian Prairie Provinces, France,
Ethiopia and Australia
Germany, Poland, and UK
Kansas in the USA, Italy, Hungry,
southern Africa, Eastern Europe
France, and Spain
(other than Hungry and Ukraine),
India, China, and Uruguay
Soybeans
Ground nuts/Peanuts China and India
Rapeseed/Canola
India and China
Sunflower
USA, Argentina, Russia, and Ukraine
[23] Maize is the most geographically ubiquitous crop
and the crop with the third largest extent in the world. It is
cultivated over 13% of the world’s croplands, with the
most extensive cultivation occurring from approximately
50°N to 45°S (Figure 5c). Maize attains its highest
cultivation intensity in the U.S. maize belt, but it is also
a major commodity in northeastern China (Manchuria),
along the Rift Valley in Africa, and in eastern Europe
(Figure 4a). Less intensive cultivation of maize can be
found in South America, western Europe, India, and
southeastern China.
[24] Barley and rye are preferentially grown in colder
latitudes, with the majority being cultivated around 55°N
(Figure 5a) in Canada, the northern United States, and
European Russia (Figures 4a and 4b). Barley is the crop
with the fourth largest area, with 9% of the world’s croplands, while rye is cultivated over 2% of the world’s
croplands.
[25] Rice, sorghum, and millet dominate the tropical
and sub-tropical belts, especially in the Northern Hemisphere (Figure 5b); these three crops occupy 11%, 3%,
and 2%, respectively, of the global cultivated area. Rice is
the second most extensive crop in the world, and is a
major crop of south and southeast Asia. It is also
cultivated in the Amazon Basin, the southern United
States, and southern Australia (Figure 4b). Sorghum, the
only cereal that does not emerge as a dominant crop in
any region, is common throughout the Rift Valley and the
Sahel region in Africa, the southern half of the Mississippi Valley, and India (Figure 4b). Millet appears in the
Ethiopia
Central and South America
(other than Brazil), Africa
Africa (other than South Africa),
Central America (other than Mexico)
same regions of Africa as sorghum and to a lesser degree
throughout parts of Asia, and is most abundant in western
India (Figure 4a).
4.2. Roots and Tubers
[26] Although roots and tubers cover a much smaller area
than cereals, they are another important human staple. The
two major crops from this category, potatoes and cassava,
are both tubers. Together they cover 4% of the world’s total
harvested area. Geographically, they are cultivated in contrasting climates (Figure 5d). Potatoes are extensively
grown in the colder temperate latitudes between 40°N and
75°N, with the highest potato cultivation intensity occurring
at 55°N in the European part of the former Soviet Union and
in northeastern Europe (Figure 4c). On the other hand,
cassava is grown in the equatorial and tropical regions
(Figure 4c). This crop is cultivated from 20°N to
30°S, but its cultivation intensity, even at its highest
(5°S), is only half that of potatoes. Cassava also appears
in northern Brazil, south central Africa, Thailand, Micronesia, and Polynesia; cassava is also the major crop cultivated in central Africa.
4.3. Sugar Crops
[27] Although sugar beets and sugar cane both produce
sugar, the similarities between the two crops end there. They
prefer different climates, with sugar cane favoring yearround warmth, while sugar beets favor much cooler conditions (Figure 5e). The two crops also have different plant
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Figure 6. Regional distribution of major crops of the world. The world is divided into 24 agriculturally
and culturally distinct regions. For each region, in a pie chart, we present the proportions of the top five
most common crops (here we include minor crops, ones for which census data were collected, but for
which no spatial data sets were generated). For completeness, we include the Islands as a region (defined
as any island in the world with an area less than 5000 km2) although they are not part of our spatial maps
or the discussion. The information for the Islands arises purely from the census data. See color version of
this figure at back of this issue.
physiologies: Sugar cane is a C4 crop, while sugar beets are
C3, and in sugar cane the sugar is stored in the stalk, while
in beets it is stored in the roots. The two sugar crops
together take up slightly more than 2% of the cultivated
croplands in the world. Sugar beets are cultivated in the
temperate latitudes of the Northern Hemisphere from 40°N
to 60°N, mostly in Europe and the European part of Russia
(Figure 4d), while sugar cane is a tropical crop, cultivated
mostly in the Caribbean and Florida, but also in Central
and South America, India, and other parts of south Asia
(Figure 4d). Minor cultivation areas for sugar beets can also
be found in the American midwest and the northeastern tip
of China, while sugar cane is also grown in Australia and
South Africa.
4.4. Pulses
[28] The FAO defines pulses as a group comprised of dry
beans, dry broad beans, dry peas, chick-peas, dry cow peas,
pigeon peas, lentils, bambara beans, vetches, and lupins.
Pulses are very important economically and provide us with
food, medicines, oils, chemicals, timber, dyes, and ornamental garden plants. They also have extremely high dietary
Figure 5. Latitudinal distribution of 18 major crops. (a) Temperate cereals (barley and rye), (b) tropical cereals (sorghum,
millet and rice), (c) most common cereals (maize and wheat), (d) tubers, (e) sugar crops, (f) pulses, (g) temperate
oil-bearing crops (soybeans, rapeseed or canola, and sunflower), (h) tropical oil-bearing crops (ground nuts or peanuts, and
oil palm fruit), and (i) cotton.
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Table 5. Regional Distribution of the Relative Crop Fraction of the Top Five ‘‘Major’’ and Three ‘‘Other’’ Crops (in %)
Region
Major
Crop 1
Major
Crop 2
Major
Crop 3
Major
Crop 4
Major
Crop 5
Sum
of 5
Other
Crop 1
Other
Crop 2
Other
Crop 3
Sum
of 8
Canada and Alaska
wheat
barley rapeseed/canola
maize
pulses
oats
linseed
mixed grain
48.1
15.9
15.0
3.9
3.0
86.0
4.6
2.2
0.9
93.7
Conterminous USA
maize
wheat
soybeans
cotton
sorghum
oats
grapes
oranges
28.0
25.5
23.9
5.3
3.9
86.6
1.8
0.3
0.3
89.0
Central America
maize
pulses
sorghum
wheat
sugar cane
coffee
oranges
bananas
46.6
12.8
8.4
4.8
4.6
77.2
7.2
1.4
0.9
86.7
Caribbean
sugar cane maize
pulses
rice
cassava
coffee
cocoa
plantains
36.1
7.8
6.2
6.0
3.8
59.9
7.2
3.6
3.3
74.0
Northern South America maize soybeans
rice
pulses
sugar cane
coffee
cocoa
oranges
23.7
18.2
8.8
8.6
7.7
67.0
6.5
1.9
1.5
76.9
Southern South America wheat soybeans
sunflower
maize
sorghum
oats
linseed
grapes
27.0
25.6
12.3
11.7
3.4
79.9
2.2
1.7
0.5
84.3
Northern Europe
barley
wheat rapeseed/canola sugar beets
potatoes
oats
linseed
mixed grain
34.7
30.9
8.8
3.7
3.4
81.5
9.8
1.0
0.7
93.0
Western Europe
wheat
barley
maize
rapeseed/canola sugar beets
grapes
oats
triticale
32.0
17.5
9.0
6.9
5.1
70.5
4.3
2.5
1.5
78.8
Southern Europe
wheat
barley
maize
sunflower
pulses
olives
grapes
oranges
21.0
16.1
6.1
5.9
1.9
51.1
15.1
9.4
1.0
76.6
Eastern Europe
wheat
barley
maize
potatoes
rye
oats
mixed grains
apples
24.7
16.8
11.2
8.2
7.2
68.2
3.6
2.1
1.6
75.5
wheat
barley
rye
sunflower
potatoes
oats
buckwheat
apples
European Russiaa
29.4
29.2
9.6
6.0
5.2
79.3
12.0
2.5
0.6
94.4
wheat
barley
potatoes
pulses
rye
oats
buckwheat
apples
Asiatic Russiaa
47.4
9.1
4.4
2.9
2.0
65.8
12.0
2.5
0.6
80.9
Northern Africa
wheat
barley
maize
pulses
rice
olives
almonds
tomatoes
30.6
18.8
6.9
3.8
3.5
63.6
11.4
1.3
1.3
77.6
Sahelian Africa
sorghum
millet
maize
pulses
groundnuts
oil palm fruit
cocoa
yams
20.0
18.9
10.5
8.3
5.2
62.8
4.1
4.0
3.2
74.0
Central Africa
cassava
maize
groundnuts
pulses
sorghum
plantains
coffee
cocoa
24.9
19.2
8.9
4.8
4.4
62.3
6.4
5.2
3.6
77.6
Eastern Africa
maize
pulses
sorghum
cassava
rice
plantains sweet potatoes
coffee
27.1
9.8
8.6
7.9
5.1
58.4
5.9
3.2
3.1
70.7
Southern Africa
maize
wheat
sunflower
sorghum
sugar cane
grapes
oranges
pumpkins
53.6
15.0
6.3
4.9
3.8
83.6
1.2
0.5
0.3
85.6
Middle East
wheat
barley
pulses
cotton
maize
grapes
olives
dates
43.4
21.0
6.8
2.7
1.9
75.7
2.6
2.2
0.9
81.4
Central Asia
wheat
barley
cotton
millet
rye
oats
buckwheat safflower seed
51.3
22.5
9.4
1.6
1.6
86.3
1.9
1.4
0.8
90.4
East Asia
rice
wheat
maize
soybeans
rapeseed
sesame
sweet potatoes
linseed
19.9
17.2
12.4
4.8
3.3
57.6
7.0
3.5
3.4
71.5
South Asia
rice
wheat
pulses
millet
sorghum
sesame seed
coconuts
mangoes
26.5
16.4
10.9
6.8
5.9
66.4
1.1
1.0
0.6
69.1
Southeast Asia
rice
maize
cassava
oil palm fruit
pulses
coconuts
natural rubber
coffee
45.8
10.4
4.0
3.7
2.7
66.7
8.0
6.5
1.4
82.6
Australia/New Zealand
wheat
barley
pulses
sorghum
sugar cane
oats
triticale
grapes
50.8
17.6
11.3
3.0
2.0
84.7
6.4
0.8
0.3
92.2
sugar cane maize
rice
cassava
oil palm fruit
coconut
bananas
sweet potatoes
Islandsb
17.5
6.5
4.2
2.8
1.3
32.3
47.6
4.7
3.2
87.8
a
The numbers under the other crops in European and Asiatic Russia are the same because sub-national data were unavailable (see Appendix A).
For completeness, here we include the Islands as a region (defined as any island in the world with an area less than 5,000 km2) although they are not
part of our spatial maps or the discussion. The information for the Islands arises purely from the census data.
b
value because they contain a higher percentage of protein
than most other plant foods.
[29] Most pulses prefer warm climates, but there are
varieties that grow in temperate regions. Pulses are broadly
cultivated from 60°N to 50°S (Figures 4d and 5f). On a
global scale, they occupy 4% of the cultivated land and, as a
group, they rank third in cultivation area, after cereals and
oil-bearing crops. The most intense cultivation of pulses
occurs around 25°N (in India, where census data on a dozen
different kinds of lentils were collected), but pulses are also
cultivated throughout Europe, parts of western Asia, the
eastern half of China, Australia, the Rift Valley in eastern
Africa, the southeastern states of Brazil, Central America,
and even in Canada.
4.5. Oil-Bearing Crops
[30] On a global scale, oil-bearing crops are grown over
10% of the cropland. According to the FAO, 10% of the
total calories available for human consumption are derived
from oil-bearing crops such as soybeans, groundnuts (or
peanuts), rapeseed (or canola), sunflower and oil palm fruit.
This percentage is slightly higher for developed countries
(12%) and slightly lower for developing countries (9%).
While oil-bearing crops are used mainly for processing into
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Table 6. Area and Relative Proportion of Seven Crop Groups
a
2
Crop Group
Area, 1000 km
Relative Fraction, %
Cereals
Roots and tubers
Sugar crops
Pulses
Oil-bearing
Fibers (cotton)
Others
Total cropland
10,955
734
419
794
1,819
534
2,664
17,920
61
4
2
4
10
3
15
100
a
The crop groups here are comprised only of the 18 major crops
considered in the study. All other crops are included in the ‘‘Others’’ group.
oil (about 79% of the world production), they are also used
for direct food consumption (11%), for seed (2%), for feed
(5%), and for industrial use (almost 1%), and 3% are wasted
[FAO/GIEWS, 2001].
[31] Oil-bearing crops exhibit a distribution pattern similar to that of cereals: Soybeans, rapeseed (or canola), and
sunflower prefer temperate latitudes, while groundnuts (or
peanuts) and oil palm fruit are their equatorial and tropical
counterparts (Figure 5g). Soybeans occupy 5% of the
world’s croplands, while rapeseed/canola and sunflower
each occupy 2% of the world’s croplands, groundnuts
occupy 1%, and oil palm fruit occupies less than 1% of the
world’s croplands.
[32] The cultivation of soybeans, especially in North and
South America, has been increasing rapidly in recent years,
and this was the only crop that had a strong positive growth
trend in the 6 years of census data collected. Soybeans are
also unique in being the only oil-bearing legume. According
to the FAO/GIEWS [2001], Asia and the Americas are the
largest producers of oil-bearing crops. These crops amount
to 50 and 34%, respectively, of the agricultural production
of the two continents. Soybean rivals maize for domination
in the maize belt of North America, but is also prevalent in
central South America (southern Brazil and northern Argentina), eastern China, and central India (Figure 4e). The
soybean belt in the United States alone is roughly the size
of Bolivia (or 1.1 million km2).
[33] Peanuts are grown in the southeastern United States
and eastern China, but the greatest intensities are found in
southern India and Gambia (Figure 4e). Rapeseed (or
canola) is most prevalent in the southern Canadian provinces, but the crop is also cultivated extensively in the entire
continent of Europe, in northwestern India, and in southeastern China (Figure 4e). Sunflowers are grown in southeastern Europe and the European part of Russia (Figure 4f),
while oil palm fruit is characteristic of some equatorial
nations, including Malaysia and Indonesia, and western
Africa (Figure 4f).
4.6. Cotton
[34] Cotton is the only major fiber considered here and
the only non-food crop. It is cultivated over 3% of the
croplands, mostly around 30°N (in the southeastern United
States and Uzbekistan, and in Tajikistan, where cotton is
the major agricultural commodity) and around 20°N (in
India and Pakistan) (Figures 4e and 5). Smaller areas of
cotton cultivation can also be found throughout southern
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South America, the southern half of Africa, and in
Australia.
4.7. Other Crops
[35] While the top five major crops together constitute
65% of the cropland, this is not necessarily true for a few
regions: the Caribbean, central Africa, East Asia, eastern
Africa, Oceania, southern Europe, and western Africa
(Table 5). To describe the agriculture of these regions better,
we present the top three minor crops (Table 5). The top
three minor (or other) crops add up to 26% of the cropland
in southern Europe, 15% in central Africa, and 14% in the
Caribbean.
[36] Of the ‘‘minor’’ crop groups, the most dominant are
fruit (with slightly more than 3% of the world’s croplands);
other oil-bearing crops such as coconut, olives, safflower,
sesame, and linseeds; other cereals such as oats and mixed
grains; and other crops such as coffee, tobacco, and cocoa
(all with slightly less than 3% of the world’s croplands)
(Table 5 and Figure 6). Vegetables, other roots and tubers,
nuts, other fibers, and spices each take up less than 2% of
the world’s cropland area.
[37] On a global scale, several minor crops have areas of
cultivation larger than some of the chosen major crops. With
over 220,000 km2, oats, a minor cereal, is 1.5 times larger in
extent than rye, a major cereal. Coffee and coconuts are
each cultivated over slightly more than 100,000 km2, an
area larger than that of both sugar beets and oil palm fruit,
both of which are considered major crops. Sweet potatoes
cover an area of 90,000 km2, but their extent is half that of
potatoes. Grapes and olives, each with over 75,000 km2, are
two other regionally significant crops that cannot be disregarded on a global scale either.
5. Diversity of the Major Crops
[38] Crop diversity is a critical factor in food security
because having a variety of crops allows for the possibility
Table 7. Area and Relative Proportion of the 18 Major Crop
Categories
Crop
Area, 1000 km2
Relative Fraction, %
Wheat
Maize
Rice
Barley
Soybeans
Pulses
Cotton
Potatoes
Sorghum
Millet
Sunflower
Rye
Rapeseed/canola
Sugar cane
Groundnuts/peanuts
Cassava
Sugar beets
Oil palm fruit
Total of major 18 crops
Others
Total cropland
4,028
2,271
1,956
1,580
927
794
534
501
501
331
290
288
283
265
247
235
154
72
15,256
2664
17,920
22
13
11
9
5
4
3
3
3
2
2
2
2
1
1
1
1
<1
85
15
100
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Figure 7. Degree of diversification of agricultural commodities. Here we map an Agricultural
Commodity Diversification Index (ACDI), which is based on the ratio of the relative crop fraction of
existing crops to the average mean relative crop fraction (see text for details). This data set only
represents the diversification in cultivation of the selected major crops in this study. See color version of
this figure at back of this issue.
that at least some crops will survive despite a poor climate,
insect outbreaks, or other natural disasters. Social factors
such as civil or economic strife, trade imbalances, and
others can compound natural disasters to further threaten
food security.
[39] For a quantitative evaluation of the global distribution
of the diversity of our chosen major crops, we define an
Agricultural Commodity Diversification Index (ACDI). This
index is based on the ratio of the relative crop fraction to the
average crop fraction of the crops that exist in each grid cell.
For each grid cell (i), the ACDI is calculated as follows:
ACDIi ¼
18 X
Fi;k
min
; 1:0 :
Mi
k¼1
Here, for each grid cell i, Fi,k is the relative crop fraction for
each of the major crops (k), and Mi is the average crop
fraction of the crops that exist in that grid cell; that is,
Mi ¼
Ni
1 X
Fi;k ;
Ni k¼1
where Ni is the number of crops in grid cell i with Fi, k > 0.
Note here that the ‘‘other crops’’ category is excluded from
ACDI, otherwise
Ni
P
Fi;k would always be 100%. Using a
k¼1
map of ACDI, we can assess the agricultural commodity
diversification for different parts of the world (Figure 7).
[40] A caveat to note first is that ACDI is scale dependent.
First, because our basic data come from administrative level
census information, differences in administrative unit sizes
will influence patterns of ACDI. By breaking down the
largest countries into subnational units (Figure 2), we have
tried to achieve a roughly uniform administrative size
throughout the world. However, major differences in
administrative unit sizes still exist. Moreover, ACDI is scale
dependent even if we are able to obtain data uniformly for
equal area units; the level of diversification can change with
scale depending on the cropping patterns. Given these
caveats, below we compare our ACDI estimates across
the world, placing emphasis on the patterns and not the
absolute values.
[41] The highest levels of major crop diversification in the
world can be found in the Andes region of South America,
Uruguay, the African nations along Gulf of Guinea, parts of
the Rift Valley, the Nile Valley, parts of the Iberian Peninsula, Ukraine, India, Pakistan, North China Plain, and
Manchuria (Figure 7). Other regions with high ACDI values
are the southeastern United States, parts of the northern
Great Plains, Venezuela, eastern Brazil, the Pampas region,
Chile, parts of western Africa, the Ethiopian highlands,
eastern Africa, much of Europe, southwestern Russia,
southeastern China, and eastern Australia (Figure 7).
[42] On the other hand, among the world’s least agriculturally diverse places are: the midwestern United States,
Montana, western Amazônia, coastal Algeria, semi-arid
southern Africa, northern Kazakhstan, Mongolia, Indochina,
Malay Peninsula, and western Australia. Relatively low
ACDI values can also be found in most of North America,
Mexico, Brazil, parts of North Africa, Sudan, Madagascar,
northern Europe, the Middle East, Bangladesh, most of
Southeast Asia, Japan, and most of Russia. Some of these
regions are heavily cultivated, although with low crop
diversification. For example, in the midwestern United States
(and the Canadian Prairie Provinces) maize and wheat make
up more than two thirds of the cropland, while in Vietnam,
Laos and Cambodia, extensive rice cultivation is found.
6. Regional Cropping Patterns
[43] In this section, we illustrate cropping patterns for
different regions of the world. We attempt to delineate the
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RAMANKUTTY ET AL.: GLOBAL CROP DISTRIBUTION
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Figure 8. Crop belts of the world. This map is derived from the three most dominant crops. A dominant
crop is one with a cultivation proportion than exceeds the mean (using the ACDI from Figure 7). If more
than three crops were dominant in a certain location (e.g., the Indian sub-continent), then we mention the
two most dominant crops and report the remainder as being mixed. See color version of this figure at
back of this issue.
world’s major growing regions, focusing on what crops or
crop combinations are dominant in each region.
[44] We use our 18 crops data sets to delineate the world’s
major crop ‘‘belts,’’ defined using a combination of the
most dominant crops (those with relative crop fractions
larger than the average relative crop fraction as calculated
for ACDI). Regions with a single dominant crop are
classified as a single-crop belt, while those with two
dominant crops form a two-crop belt, and those with three
dominant crops form a three-crop belt. In regions with
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Figure 8. (continued)
more than three dominant crops, we label the two most
dominant crops and label the remainder as being ‘‘mixed’’
(Figures 8a – 8c).
6.1. North America
[45] North America is composed of large, agriculturally
homogeneous regions (Figure 7). Three major features stand
out: two wheat belts and a maize belt in the north gradually
transitioning into a soybean belt in the south (Figure 8a).
[46] The North American wheat belt dominates this
region by far; wheat makes up 30% of the cropland in this
region (Table 5 and Figure 6). There are two wheat belts
extending west of the Mississippi and spanning the southern
Prairie Provinces in Canada and the Great Plain states in the
United States (the two belts being separated by the states of
South Dakota and Nebraska) (Figure 8a). Winter wheat is
cultivated predominantly south of Nebraska, where it is
planted in September through October and harvested in June
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Figure 8. (continued)
through July of the next year. In contrast, spring and durum
wheat, which are cultivated predominantly north of
Nebraska, are planted in April through May and harvested
in mid-July through mid-September of the same year
[USDA/JAWF, 1994]. Although wheat dominates these
two belts, there are a variety of secondary crops cultivated;
barley and canola are grown in the northern portions of the
North American wheat belt, maize is grown in the central
part, and sorghum and cotton are grown in the south.
[47] The maize belt is dominant in the lower half of the
Missouri River basin and the entire region east of the
Mississippi (Figure 8a). Here maize is planted April through
May and harvested October through November [USDA/
JAWF, 1994]. Throughout the maize belt, there is a single
secondary crop, soybeans, which often rivals maize for
dominance. In the Midwest, the maize belt in Wisconsin
transitions into a maize-soybean belt in Iowa and Illinois,
and then into a soybean belt in Missouri.
[48] Soybeans make the third most prominent crop belt in
North America. This crop dominates the lower half of the
Mississippi as far east as the Carolinas (Figure 8a). This
region has a similar but somewhat wetter and warmer
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RAMANKUTTY ET AL.: GLOBAL CROP DISTRIBUTION
climate than that of the maize belt. Soybeans are planted
slightly later than maize (May through June) but harvested
around the same time (October through November) [USDA/
JAWF, 1994]. Throughout the soybean belt, the secondary
crops are cotton and wheat.
[49] The other important crops in North America are
barley (which together with wheat forms a wheat-barley
belt in the Canadian province of Alberta) and cotton (which
dominates the cropland along the Gulf Coast with the
exception of Florida, and forms a cotton or cotton-sorghum
belt in Texas and cotton-groundnuts belt in Georgia).
Florida is dominated by sugar cane, making this region
agriculturally similar to the rest of the Caribbean, rather
than to continental North America. The state of Georgia also
contains a small groundnuts belt.
6.2. Central America and the Caribbean
[50] Central America has varied agroclimatic settings.
However, a single crop, maize, dominates the region from
central Mexico to Nicaragua inclusively (Figure 8a). In the
dry climate of northwestern Mexico, maize is planted in
September and October and harvested January through
March of the next year [USDA/JAWF, 1994]. In Mexico,
maize forms crop belts with three other crops: sorghum in
the state of Tamaulipas, pulses in Coahuila, and wheat in
Sonora. Throughout the Central American maize belt,
pulses are the next most dominant crop, followed by sugar
cane.
[51] Costa Rica’s croplands are a transitional area with a
mixture of maize, pulses, and rice being cultivated throughout the country (Figure 8a). Rice forms a much smaller
second crop belt in Costa Rica and Panama, with maize as
the secondary crop, although the average annual temperature and precipitation in this region are not much different
from those to the north. The Caribbean is dominated by
sugar cane (Figure 8a). In this region with a steady yearround climate, sugar cane is planted and harvested almost
throughout the entire year (November through May)
[USDA/JAWF, 1994]. Rice and maize are the secondary
crops throughout the Caribbean. Although not considered a
major crop in this study, coffee is a key commodity in the
Caribbean and accounts for 7% of the cultivated land (a
percentage higher than that of the third most dominant
major crop).
6.3. South America
[52] South America has far more diverse cultivation than
North and Central America (Figure 7). Here maize and
soybeans rival for dominance in the northern portions of the
continent, while wheat dominates in the south.
[53] One maize belt is draped over the entire Andes and
the lowlands to their west from the Columbian highlands
all the way into Argentina’s Patagonia, and another centers
on the Brazilian Highlands in southeastern Brazil (Figure 8a).
Here maize is planted March through May and harvested
October through December [USDA/JAWF, 1994]. While
maize is a major dominant crop in Central America, the
Andes, and the Brazilian Highlands, it is surpassed by wheat
and soybeans in the La Plata region of South America.
Throughout the Andean maize belt the secondary crops
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are rice (in the Columbian and Ecuadorian lowlands
west of the Andes), potatoes (throughout the Peruvian and
Bolivian Andes), and sunflowers (in the southern Andes of
Argentina). In the Brazilian Highlands, sugar cane and
soybeans complement the maize belt.
[54] Soybeans form the next largest belt in South America
(Figure 8a). This crop is extensively cultivated in the central
portion of the continent from the Brazilian state of Mato
Grosso in the north to the Argentinean state of Cordoba in
the south, in the Gran Chaco region and the area east of it.
Soybeans in this region are planted in the beginning of the
wet season (October through December) and harvested at
the end of it (March through May) [USDA/JAWF, 1994].
The secondary crops throughout this soybean belt are maize
in Brazil, cotton in Paraguay, and a combination of wheat,
maize, and sunflower in Argentina.
[55] Wheat forms the third largest crop belt in South
America, but it is the major crop in the southern part of
the continent in Argentina and Chile (Figure 8a). Wheat
covers the pampas of Argentina and the Western Coastal
Plain of Chile. As opposed to the maize and the soybean
cultivation areas in South America, the regions of wheat
cultivation do experience frosts. Wheat in this region is
planted May through July and harvested mid-November
through mid-January [USDA/JAWF, 1994]. Throughout the
South American wheat belt in the pampas of Argentina,
soybeans and sunflowers form the secondary crops, while
throughout the South American wheat belt in Chile, the
secondary crop is maize.
[56] In addition to maize, soybeans, and wheat, there are
several other major crop belts in South America. Although
sunflowers are cultivated in other parts of the world, South
America has the only sunflower belt (Figure 8a). In fact
sunflowers are the third-ranking crop in southern South
America, surpassing maize, with 12% of the cropland. Also,
the northern coastline of the continent and the Tocantins
river basin are regions of rice cultivation, while the Xingú
river basin is a region of cassava cultivation (Figure 8a). In
Brazil the region between Serra do Piaui and the town of
Recife makes up a small pulses belt, while south of São
Paulo has a sugar cane belt (Figure 8a).
6.4. Europe
[57] Europe, like North and Central America, is also
composed of large homogeneous agricultural zones
(Figure 7). The top five most common major crops for the
continent as a whole (wheat, barley, maize, potatoes, and
sunflower) represent 63% of the croplands (Table 5). The top
five most common major crops for the continent as a whole
(wheat, barley, maize, potatoes, and sunflower) represent
63% of the croplands (Table 5). Most locations in Europe
can benefit from two harvests. Winter grains (winter wheat,
winter barley, and rye) are planted September through
October and harvested mid-June through August of the next
year, and spring grains (maize, spring barley, and most oats)
are planted April through May and harvested September
through October of the same year [USDA/JAWF, 1994].
[58] Wheat is cultivated across the entire European continent, except for the Iberian Peninsula, Belarus, and the
Baltic Republics (Figure 8b). While most of the wheat
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cultivated throughout this region is winter wheat, durum
wheat is also grown here. Winter wheat is most often
cultivated in combination with winter barley and rye, and
is also most often cultivated on the same land (doublecropped) with maize, oats and to a lesser extent with spring
barley [USDA/JAWF, 1994]. Throughout southern Europe,
spanning France, Italy, Hungary, Moldova, and all countries
south of there, the secondary crop is maize. To the north, in
Croatia, Bosnia and Herzegovina, northern Serbia, and
Romania, can be found a maize-wheat belt. In Poland, the
much more cold-tolerant rye can be found as the secondary
crop. In this northern sub-region, barley and rye are also
found. Throughout Poland, the Russian oblast of Nizhny
Novgorod, and the surrounding regions the croplands can
be described as a mixture of wheat, barley, rye, and
potatoes.
[59] Second in size in Europe is the area of barley
cultivation (Figure 8b). Winter barley is the dominant crop
on the Iberian Peninsula, especially in Spain, and is surrounded by barley-wheat and wheat alone belts. The spring
barley belt is found in Belarus, the Baltic Republics, and the
European part of Russia. Ireland stands alone in having both
spring and winter barley cultivation. Throughout the barley
belts, the secondary crops are wheat, potatoes, and rye.
[60] The region along the Mediterranean Sea has a distinct
climate. While wheat and barley are the top crops, a minor
crop, olives, occupies a large portion of the region’s
cropland (over 43,000 km2 or 15%). In this region, fruits
come next in the other categories with 40,600 km2, of which
area 65% is in grapes, 7% in oranges, and 6% in peaches
and nectarines.
6.5. Africa
[61] With 13% of the global harvested area, Africa has less
cropland than any other part of the world. The agroclimatological zones in Africa are very diverse, ranging from the dry
and barren desert, through the rich soil of the Rift, Nile, and
Niger Valleys, to the southern extremes. But unlike any other
parts of the world, there are no large crop belts in Africa.
Rather, there are agricultural regions within which different
combinations of crops are cultivated (Figure 8b).
[62] Northern Africa is characterized by a Mediterranean
climate with the alternation of pronounced warm dry and
cool wet seasons. Morocco, Algeria, Libya, and Tunisia
have large crop areas along the coast, dominated by a
mixture of wheat and barley (Figure 8b). With a single
growing season, both winter wheat and barley are planted
November through December and harvested May through
June of the next year [USDA/JAWF, 1994]. In the Nile delta
and Nile Valley, wheat, maize, and rice form a unique
agricultural belt (Figure 8b). Again, akin to southern
Europe, olives are a major crop in this region, representing
11% of the cropland.
[63] The Sahel region, with low rainfall, is dominated by
the drought resistant millet and sorghum. In Senegal,
Gambia, and Guinea-Bissau another drought resistant crop,
groundnuts or peanuts, is grown. Maize and a mixture of
other crops are also found in northern Nigeria (Figure 8b).
With a single growing season in the Sahel, most crops are
planted May through July and harvested October through
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November [USDA/JAWF, 1994]. Coastal West Africa has a
more moderate climate because of the oceanic influence and
thus benefits from two growing seasons. The dominant
crops here are hydrophilic: rice from Guinea to Liberia
and maize from the Ivory Coast to Nigeria. Here the first
crop of rice is planted April through May and harvested
August through October, and a second crop of rice is
planted November through December and harvested March
through April. Maize is also cultivated in two crops, with
the first one being planted March through April and
harvested June through August, and the second being
planted August through September and harvested December
through January [USDA/JAWF, 1994]. The secondary crop
throughout Africa’s West Coast rice belt is cassava, while in
the maize belt it is a mixture of sorghum, rice, cotton, and
millet. Since the agricultural area along the western coast of
Africa is much smaller than the one in the Sahel, rice is not
one of the top five crops in Sahelian Africa (Figure 6).
However, maize is the third most dominant crop, after
sorghum and millet, occupying 11% of the cropland in this
region (Table 5).
[64] Directly east of the Sahel, in Ethiopia, is the northern
tip of the African Rift Valley. Throughout the Rift Valley,
maize is the dominant crop (Figure 8b). The only locations
where maize is not dominant are Zaire (where cassava and
cassava-maize-pulses are the prevalent combinations),
Mozambique (where cassava dominates), and the drier
Botswana and Namibia (where sorghum and millet, respectively, are the crops of choice). Throughout eastern Africa,
maize is a winter crop generally planted March through
June and harvested August through December, while in
South Africa, maize is a summer crop planted October
through December and harvested April through June. With
water being the limiting factor throughout eastern Africa,
the secondary crop is cassava (in Tanzania, Angola, Zambia,
and Mozambique), pulses (in Uganda and Tanzania), sorghum (in Mozambique), and cotton (in Zimbabwe, with
somewhat better irrigation facilities). South Africa, on the
other hand, benefits from a second crop of winter wheat that
is planted May through July and harvested October through
December [USDA/JAWF, 1994]. The island of Madagascar
benefits from two growing seasons, and the most dominant
crop is rice, followed by cassava and maize. Rice here is
planted November through mid-January and harvested April
through June. The two winter crops in this area are wheat
and sweet potatoes. The former is planted in May and
harvested in November, and the later is planted mid-February through mid-May and harvested mid-May through midDecember [FAO/GIEWS, 2001]. There is a ’’minor’’ crop
that should be included for a more complete regional
picture; plantains occupy a significant portion of the croplands in both eastern and central Africa, representing about
6% of the cropland (Figure 6 and Table 5).
6.6. Middle East
[65] The dominant crop in the Middle East is wheat,
cultivated from Turkey in the west to Iran in the east and
along the Mediterranean coast, briefly interrupted by a
combination of barley and wheat in Syria (Figure 8b).
Winter wheat and barley are planted mid-September
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through December and harvested April through August
[USDA/JAWF, 1994]. With a far smaller proportion (7%
of the cropland) pulses are the third major crop in the
Middle East, cultivated in the summer together with maize
in northern Turkey, with cotton along the Turkey-Syria
border, and with sunflowers in western Turkey.
6.7. Asia
[66] Rice dominates this region with 24% of the cropland.
The Asian rice belt stretches from India and Nepal on the west
to Japan, South Korea, and Taiwan on the east, from the
Yangtze River in the north to Timor in the south (Figure 8c).
This area receives ample precipitation from the monsoons.
Throughout this region, farmers plant a single crop of rice in
April and May and harvest it in August through October;
however, several sub-regions plant multiple crops of rice
[USDA/JAWF, 1994]. Rice is double cropped in southeastern
China, along the final stretches of the Xun Xi River,
throughout most of Indochina, in the eastern half of India
and the Ganges floodplain, and on the island of Java.
Throughout parts of Bangladesh, in the Ganges-Brahmaputra
floodplain, three crops of rice are cultivated. This large
crop belt is dominated almost exclusively by rice, but there
is a large number of diverse secondary crops: wheat, maize,
groundnuts, and sugar cane in China; maize, cassava and
pulses in Indochina; wheat in Nepal; wheat, pulses, and
groundnuts in India; and maize in Indonesia.
[67] With only a slightly smaller area (19% of the
cropland), wheat forms the second largest crop belt in Asia.
This crop is characteristic of the Indus River Valley in
Pakistan, the Huang He River Valley in China, and most of
Central Asia with the exception of Turkmenistan, Uzbekistan, and the southern parts of Kazakhstan (Figure 8c). In
Pakistan and northwestern India, winter wheat is planted
October through December and harvested March through
May. In the Huang He River Valley, spring wheat is planted
in March and April and harvested in mid-July through midAugust, but winter wheat accounts for 85 – 90% of the
wheat and is planted mid-September through October and
harvested in June. In Kazakhstan and the Russian oblasts
north of it, winter wheat is planted in September and
harvested mid-July through August, but spring wheat is
the larger crop and is planted in May and harvested midAugust through September [USDA/JAWF, 1994]. Unlike in
the Asian rice belt, secondary crops are far fewer in the
wheat belt. In the Indus River Valley, the major secondary
crop is cotton, in the Huang He River Valley it is maize, and
in Kazakhstan and the Russian oblasts north of it the major
secondary crop is barley.
[68] In Asia, maize is grown in small pockets of dominance (Figure 8c). It is the dominant crop in two of the
northeastern Chinese provinces of Jilin and Liaoning. To the
north, this area transitions into a maize-wheat-soybean area
and then into a soybean-maize-wheat area, while to the
west, it progresses into a wheat-maize and later into a wheat
cultivation area. The secondary crop throughout this area is
rice. China has another maize pocket in the southern
province of Yunnan; this stands alone in the middle of the
Asian rice belt, and the secondary crop here is wheat.
Finally, together with rice, maize forms the dominant crop
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combination in the Philippines, where cassava and sugar
cane compete for third and fourth place. While for Asia as a
whole, maize represents 7% of the cropland, this crop is one
of the top five only in East and Southeast Asia (Table 5 and
Figure 6).
[69] Together with rice and wheat, pulses form a dominant crop complex in western India. In Asia as a whole, they
represent 6% of the cropland, but in India, this proportion is
12%. Here they are the third most important major crop
after rice and wheat, and the area they cover is about half
that of rice and about equal to the area of wheat. Pulses are
also the secondary crop in Myanmar and a tertiary crop in
North Korea and several southern Russian oblasts.
[70] Several other crops form a number of small crop belts
(Figure 8c). Potatoes dominate in far northeastern Russia,
barley is the most dominant crop in parts of southeastern
Kazakhstan, a combination of cotton and wheat dominates
Uzbekistan, and oil palm fruit stands out in Malaysia. India
alone has the most diverse combination of crop belts.
Groundnuts stand out in Gujarat; millet in Gujarat and
Rajasthan; a combination of pulses, rice, and wheat exists
in Madhya Pradesh, with the agriculture of the rest of this
state being a mixture of more than three crops; sorghum
dominates the state of Maharashtra; while rice spreads along
the southern and eastern coast.
6.8. Australia and New Zealand
[71] The agriculture of this region closely resembles that
of the other temperate regions of the world. Wheat dominates Australia (Figure 8c); it is interrupted only briefly by a
combination of wheat and barley in the area around Adelaide. Winter wheat here is planted May through July and
harvested October through December [USDA/JAWF, 1994].
In the western portion of the Australian wheat belt, pulses
are the most prominent secondary crop, while barley is the
secondary crop in the eastern portions. Winter barley is also
the most dominant crop in New Zealand, forming its own
belt there; it is planted April through June, and harvested
November through January. Wheat is the secondary crop in
New Zealand. Pulses are the third crop category with a
significant enough proportion to be included here (11%).
7. Summary and Conclusions
[72] Agricultural activities have been one of the most
important drivers of global environmental change in recent
decades and centuries. To assess the consequences of
cultivation practices for global food production and the
health of the environment, data sets of the worldwide extent
and intensity of agricultural land use and land cover change
are critically needed. While remotely sensed data are able to
delineate some of the patterns of agricultural land cover,
they are unable to distinguish some of the important features
of agricultural land use practices such as the different types
of cropping systems (crop varieties, crop rotations, intercropping, multiple cropping), agricultural inputs (irrigation,
fertilization, machinery), and outputs (yield, production).
Such information is critically needed for studying the
consequences of food production systems on the global
biogeochemical cycles, global and regional climate, and
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food security; only ground-based data sources, such as
agricultural censuses, contain the necessary information.
[73] In this study we have synthesized crop specific
agricultural census data and spatially explicit data on the
extent of the world’s croplands to generate global data sets
for the distribution of 18 major crops. Although the study
uses a simplified approach with several assumptions, it
succeeds in producing a ‘‘first cut’’ global data set that is
generally consistent with common agricultural knowledge.
Quantitative validation of the data set has not been possible
due to the lack of good alternative data sources for many
regions of the world. However, we have qualitatively
compared our data sets to a recent publication on the
distribution of major crops of the world by the U.S.
Department of Agriculture; the comparison reveals the
major consistencies between the data sets, as well as the
deficiencies in our approach.
[74] This study shows that the selected 18 major crops
(barley, maize, millet, rice, rye, sorghum, wheat, cassava,
potatoes, sugar beets, sugar cane, pulses, soybeans, groundnuts/peanuts, rapeseed/canola, sunflower, oil palm fruit,
and cotton) are representative of the agriculture of most
regions in the world. In certain regions however, one would
need to include other crops to obtain a more complete
picture (i.e., oats for many parts of the world and grapes
and olives in the Mediterranean) (Table 5). Using the crop
cover data, we were able to objectively delineate the major
crop belts of the world (Figure 8). The location of these crop
belts is also in concert with the rest of the agricultural
literature. Some continents are composed of large agriculturally homogeneous zones (North America, Europe, Asia,
the Middle East, Australia, and New Zealand), while others
truly are tapestries of crop mixtures (South America and
Africa).
[75] These crop data sets have a wide range of applications. They can be used within global ecosystem models
and climate models, to assess global food production
systems (food production, food security), global water use
(irrigation water requirements, impacts on water quality),
and consequences for global climate and biogeochemical
cycles. Digital versions of these major crop data sets will be
made available through our web site (http://www.sage.wisc.
edu) upon publication of this paper.
Appendix A. Compilation of Crop Inventory
Data: Assumptions Made in Countries With
Unavailable Sub-National Data
A1. Andora
[76] There are no FAO data for Andora. Therefore, to
obtain the proportion of harvested area of each crop to the
total harvested area, we used an area-weighted average of
data for each particular crop from France and Spain.
A2. Argentina
[77] In Argentina, census data were available only for the
following states: Entre Rios, Buenos Aires, San Luis, La
Pampa, Santa Fe, and Cordoba. For the remaining states, we
used an area-weighted average of data from the known
states. For cotton, only national level data were available.
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This was distributed among the states in proportion to the
total harvested area of the remaining major crops.
A3. Australian Capital Territory
[78] In the Australian Capital Territory, we assumed the
proportions of each of the 18 crops to the total to be the
same as those of the Australian state of New South Wales.
A4. Brazilian Litigated Zone
[79] In the Brazilian Litigated Zone, to obtain the proportion of each crop to the total, we used an area-weighted
average of that particular crop from the Brazilian states of
Ceara, Piaui, and Amazonas.
A5. Canadian Northwest and Yukon Territories
[80] In the Canadian Northwest and Yukon Territories, to
obtain the proportion of each crop to the remaining, we used
an area-weighted average from the Canadian provinces of
Alberta and British Columbia. Also, state-level data for
pulses were available only for dry peas and dry beans. The
sum of these data was scaled up to match the FAO nationallevel statistics for pulses.
A6. Kazakhstan
[81] For Kazakhstan, only national level data on barley
were available. This was distributed among the oblasts in
proportion to the total harvested area of the remaining major
crops.
A7. Liechtenstein
[82] In Liechtenstein, as FAO data were not available, to
obtain the proportion of harvested area of each crop to the
total, we used an area-weighted average of data for particular crop from Austria and Switzerland.
A8. Luxembourg and Belgium
[83] The agricultural census data for Luxembourg and
Belgium were reported together; therefore, we assumed the
two countries to have the same crop proportions for all crops.
A9. Montenegro
[84] In Montenegro, to obtain the proportion of each crop
to the remaining, we used an area-weighted average of that
particular crop from Albania, Bosnia, and Herzegovina.
A10. Russia
[85] In Russia, barley data were only available for regions
(group of oblasts). This was uniformly distributed among
the oblasts within each region. Only production data were
available for rye (in tons). Knowing the total harvested area
at the national level from FAO statistics, and assuming that
yield is relatively constant among the different oblasts
where this crop is cultivated, we estimated harvested area
for each oblast.
A11. San Marino
[86] In San Marino, as FAO data were not available, we
assumed the proportions of each of the 18 crops to the total
to be the same as those of Italy.
A12. Serbia
[87] For Serbia, to obtain the proportion of each crop to
the total, we used an area-weighted average of that partic-
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RAMANKUTTY ET AL.: GLOBAL CROP DISTRIBUTION
ular crop from Albania, Bosnia and Herzegovina, Croatia,
Bulgaria, Hungry, Macedonia, and Romania.
A13. Taiwan
[88] In Taiwan, we assumed the proportions of each of the
18 crops to the total to be the same as those of the Fujian
province in China.
A14. District of Columbia and Guantanamo Bay
[89] The cropland area in the District of Columbia in the
United States and Guantanamo Bay of the United States is
negligible, and therefore we assumed the cropland proportions for all crops to be zero.
A15. West Bank
[90] In the West Bank, we assumed the proportions of each
of the 18 crops to the total to be the same as those of Israel.
[91] Acknowledgments. We would like to thank Tom Lillesand and
Jun Zhu for fruitful discussions and advice during this project. We would
like to thank Lex Bouwman for providing the RIVM crop data sets. The
two reviewers of this paper provided very constructive suggestions that
greatly improved the quality of the final manuscript. This work was
supported by NASA’s Office of Earth Science (through Interdisciplinary
Science (IDS) Program grant NAG5-9452).
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Figure 1. Global cropland data set of Ramankutty and Foley [1998]. This data set was created by
merging satellite-derived land cover data and administrative unit level agricultural census data. It
represents the fraction of a 5-min resolution (in latitude by longitude) grid cell occupied by arable lands
and permanent crops in 1992.
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Figure 6. Regional distribution of major crops of the world. The world is divided into 24 agriculturally
and culturally distinct regions. For each region, in a pie chart, we present the proportions of the top five
most common crops (here we include minor crops, ones for which census data were collected, but for
which no spatial data sets were generated). For completeness, we include the Islands as a region (defined
as any island in the world with an area less than 5000 km2) although they are not part of our spatial maps
or the discussion. The information for the Islands arises purely from the census data.
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Figure 7. Degree of diversification of agricultural commodities. Here we map an Agricultural
Commodity Diversification Index (ACDI), which is based on the ratio of the relative crop fraction of
existing crops to the average mean relative crop fraction (see text for details). This data set only
represents the diversification in cultivation of the selected major crops in this study.
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Figure 8. Crop belts of the world. This map is derived from the three most dominant crops. A dominant
crop is one with a cultivation proportion than exceeds the mean (using the ACDI from Figure 7). If more
than three crops were dominant in a certain location (e.g., the Indian sub-continent), then we mention the
two most dominant crops and report the remainder as being mixed.
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Figure 8. (continued)
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Figure 8. (continued)
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