Center for Sustainability and the Global Environment (SAGE), University of Wisconsin, Madison, WI 53726, USA.
Proc Natl Acad Sci U S A. 2010 Nov 16;107(46):19645-8. doi: 10.1073/pnas.1011078107. Epub 2010 Nov 1.
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.
开垦农田以满足不断增长的人口、饮食变化和生物燃料生产的需求，这是以减少自然植被和土壤中的碳储量为代价的。在这里，我们对碳储量和当前作物产量之间的权衡关系进行了全球范围的空间分析。不同地区之间的差异非常明显。例如，每开垦一单位土地，热带地区损失的碳量（约 120 吨/公顷）几乎是温带地区的两倍（约 63 吨/公顷），而作物年产量则不到温带地区的一半（1.71 吨/公顷·年）与 3.84 吨/公顷·年）。因此，与在温带地区开垦同样面积的土地相比，热带地区新开垦的土地每生产 1 吨作物年产量，就会排放近 3 吨碳。通过将作物产量纳入分析，我们明确了所有当前种植作物地区的碳储量与作物之间的权衡关系，从而相对于以前的区域估计，大大提高了空间分辨率。特别是在热带地区，应重点提高现有耕地的产量，而不是开垦新土地。我们的高分辨率方法可用于确定当地土地利用决策的净效应。
