Impacts of land cover change: Energy regulation, breadbasket production, and precipitation.

摘要

Human activities are a major influence on the Earth's environment. Perhaps the most apparent factor of this influence is the impact on the physical state of the land surface itself. With terrestrial vegetation influencing climate on variety of scales through biogeophysical exchanges of water and energy, the widespread conversion of land cover has played a vital role in the evolution of recent climate. In this dissertation, I examined the potential impacts that changes in land cover have on energy, moisture, and food production using a combination of computational models and observations.;The Amazon Rainforest is a region that is currently experiencing extensive land cover change. Additionally, the southern portion of the region has experienced two "once in a century" level droughts in the past six years. Using a series of twelve high-resolution mesoscale model simulations, the biogeophysical impacts of Amazonian deforestation on regional hydrology and climate under varied rainfall regimes were tested. In particular, backtrajectories of water vapor were analyzed to focus on how changes in evapotranspiration due to land cover change may enhance or diminish drought or pluvial conditions, and how these changes may influence ecosystem services.;A limitation of using high-resolution mesoscale models to assess the impacts of deforestation are the extensive computational requirements needed to complete a limited set of scenarios. With this in mind, a new land surface and boundary layer model is presented. This model was designed to be capable of assessing the biogeophysical impacts of land cover change under multiple scenarios with limited computational requirements and reduced numbers of unknown parameters. Using this model, the global biogeophysical influence of vegetation on near surface climate regulation was tested. Finally, taking advantage of the crop modeling capabilities of the model I examined the potential for land cover change to influence crop yields in the major breadbasket regions of the world, and found the potential to be similar in magnitude to that expected with greenhouse induced warming.