Agricultural land use and its Earth system implications

农用地利用面临两难境地。一方面，人类通过土地利用获取有价值的资源，如食物、纤维和淡水。另一方面，土地利用和覆盖的变化是全球环境变化的主要驱动力，这反过来可能危及我们未来持续获取资源的能力。 在过去的40年里，我们全球粮食产量的大部分增长是通过农业集约化(即通过使用新的作物品种和更多的投入，如灌溉和化肥来提高单位土地产量)，而不是通过延伸(扩大生产面积)。关于集约化与扩大化的好处，有一场激烈的辩论，主要是在环保界。一方面，延伸化允许“野生动物友好型”耕作。但集约化，通过总体上使用更少的土地，可能会让我们“为自然腾出土地”。然而，这场辩论对其他环境问题也有意义，这一点还没有得到广泛认识。虽然延伸化会导致二氧化碳排放(通过砍伐森林)和生物多样性的丧失，但集约化会导致一氧化二氮排放(另一种强有力的温室气体)，以及淡水枯竭和污染。因此，任何一种选择都会带来一系列不同的环境问题。 我的研究计划的目的是在集约化-扩大化辩论的内容中检查作物生产和全球环境之间的权衡。我建议开发应对这一挑战所需的全球数据集和建模工具。我还建议在巴西亚马逊、印度和加拿大这三个案例研究地区进行更有针对性的工作，这三个地区被选为考虑一系列农业系统和环境问题的案例研究地区，以检查已经做出的历史权衡，并探索未来可能的权衡。

Agricultural land use presents a dilemma. On the one hand, humans derive valuable resources such as food, fiber, and freshwater through land use. On the other hand, land use and cover change is a major driver of global environmental change, which may, in turn, jeopardize our continuing ability to derive resources in the future. Over the last 40 years, most of our global increase in food production has come through agricultural intensification (i.e., extracting higher production per unit of land by using new varieties of crops and more inputs such as irrigation and fertilizers) rather than through extensification (expanding area under production). There is a raging debate, mainly among the conservation community, about the benefits of intensification versus extensification. On the one hand, extensification allows for "wildlife friendly" farming. But intensification, by using less land overall, may allow us to "spare land for nature". However, this debate also has significance for other environmental issues, which has not been widely recognized. While extensification results in carbondioxide emissions (through deforestation), and biodiversity loss, intensification can cause nitrous oxide emissions (another potent greenhouse gas), and freshwater depletion and pollution. So either option presents a different suite of environmental problems. My research program aims to examine the tradeoffs between crop production and the global environment in the content of the intensification-extensification debate. I propose to develop global data sets and modeling tools necessary to address this challenge. I also propose to do more focussed work in the Brazilian Amazon, India, and Canada, three case-study regions chosen to consider a range of farming systems and environmental problems, to examine the historical tradeoffs that have already been made and explore potential future tradeoffs.