Trading carbon for food: Global comparison of carbon stocks vs. crop yields on agricultural land

Abstract

Expanding croplands to meet the needs of a growing population, changing diets, and biofuel production comes at the cost of reduced carbon stocks in natural vegetation and soils. Here, we present a spatially explicit global analysis of tradeoffs between carbon stocks and current crop yields. The difference among regions is striking. For example, for each unit of land cleared, the tropics lose nearly two times as much carbon (∼120 tons·ha −1 vs. ∼63 tons·ha −1 ) and produce less than one-half the annual crop yield compared with temperate regions (1.71 tons·ha −1 ·y −1 vs. 3.84 tons·ha −1 ·y −1 ). Therefore, newly cleared land in the tropics releases nearly 3 tons of carbon for every 1 ton of annual crop yield compared with a similar area cleared in the temperate zone. By factoring crop yield into the analysis, we specify the tradeoff between carbon stocks and crops for all areas where crops are currently grown and thereby, substantially enhance the spatial resolution relative to previous regional estimates. Particularly in the tropics, emphasis should be placed on increasing yields on existing croplands rather than clearing new lands. Our high-resolution approach can be used to determine the net effect of local land use decisions.cropland expansion | deforestation | greenhouse gases | ecosystem services | land use change

Biomass turnover time in terrestrial ecosystems halved by land use

“…We did this by using the minimum and maximum value per grid cell of the three biome maps and our best-guess map. A published carbon stock map 88 was used as a third SCpot map.…”

Measuring the relative importance of different agricultural inputs to global and regional crop yield growth since 1975

“…For example, most of the globe's 1975 to mid-2000s growth in cropland extent occurred in the tropics (Table 4). Further, the decline in the overall quality of cropped soil has been more dramatic in the tropics as more and more tropical forest area and their poor soils have been used for crops since 1975 26 .…”

Toward a whole-landscape approach for sustainable land use in the tropics

“…sensitive to improvements in yields than to reduced deforestation. West et al (15) underscore the need to increase yields in the tropics to alleviate the current situation in which a unit of cleared land in the tropics loses nearly twice as much carbon and produces less than half the crop yield compared with temperate regions. A notable exception to this general conclusion is the high-input farming practices in the southern Amazonian agricultural frontier (16,23).…”

“…Thomson et al (13), Angelsen (14), and West et al (15) take global-scale views of the linkages between food production and climate mitigation. Thomson et al use an integrated modeling approach to understand potential outcomes from climate mitigation policies combined with scenarios of growth in agricultural productivity.…”