Mapping contemporary global cropland and grassland distributions on a 5 × 5 minute resolution

Abstract 

This paper describes the development of agricultural land cover maps with 5 × 5 minute resolution based on satellite data and agricultural statistics from the Food and Agriculture Organization (FAO) for the period 1990-2000. Consistency with the FAO data allows for reconstructing past changes and developing scenarios for future changes in land cover. Two base maps were used:

1. the International Geosphere-Biosphere Programme (IGBP) map based on DISCover data using the IGBP classification
2. the Global Land Cover (GLC) map based on the Global Land Cover 2000 VEGA2000 data.

The underlying DISCover data from the seasonal land cover regions were used to allocate the areas of cropland and grassland for the IGBP map. For the GLC map no such data were available, so a trial and error approach was used. While neither of the two base maps completely matched the FAO country data, combination of the IGBP and GLC maps resulted in a satisfactory match with FAO data for all countries.

Apart from noise in the data, interpretation problems and uncertainties in the ancillary data used in interpretation, a major problem in allocating grasslands is the broad definition used by FAO, allowing for important differences between countries in the type of grassland included in the statistics. Comparison with Holdridge life zones showed that a large part (40%) of global grassland occurs in semi deserts, deserts and sub-polar tundra's, regions with unfavorable climates with low productivity and low carrying capacity. However, the distribution of grasslands over life zones varies widely in different parts of the world. Cropland occurs in more favorable climates.