Agricultural land use and its Earth system implications

农业用地面临两难境地。一方面，人类通过土地利用获取食物、纤维和淡水等宝贵资源。另一方面，土地使用和覆盖的变化是全球环境变化的主要驱动力，而这反过来又可能危及我们今后获取资源的持续能力。 在过去的40年里，我们全球粮食生产的大部分增长都是通过农业集约化（即，通过使用新的作物品种和更多的投入，如灌溉和化肥，而不是通过扩展（扩大生产面积），提高每单位土地的产量。有一个激烈的辩论，主要是在保护社区，关于集约化与扩展化的好处。一方面，扩大种植范围可以实现“野生动物友好型”农业。但是集约化，通过减少土地的使用，可以让我们“为自然腾出土地”。然而，这场辩论对其他环境问题也有意义，这一点尚未得到广泛认识。扩张导致二氧化碳排放（通过砍伐森林）和生物多样性丧失，而集约化则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不同的环境问题。 我的研究项目旨在研究在集约化-扩展化辩论的内容中作物生产和全球环境之间的权衡。我建议开发全球数据集和建模工具，以应对这一挑战。我还建议在巴西亚马逊，印度和加拿大，三个案例研究地区选择考虑一系列的农业系统和环境问题，做更多的重点工作，研究已经取得的历史权衡，并探索潜在的未来权衡。

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.