| Expansion of the human appropriation of net primary production (HANPP) is a future certainty, given a growing global food demand -- driven by near-exponential population growth coupled with increasing global meat consumption -- and an increasing global investment in bioenergy - promoted by nearly all global energy policy. Yet, our current understanding of the impacts associated with increased HANPP is limited and the subject of intense debate in the scientific community. The focus of my dissertation is to improve our understanding of the impacts of, and future potential for, HANPP through the use of satellite data and landuse modeling.;In chapter 1, I develop a framework to evaluate global bioenergy potential using Moderate Resolution Imaging Spectroradiometer (MODIS) net primary productivity (NPP) data in an effort to put fundamental quantitative sideboards on the overall potential for global bioenergy production. In chapter 2, I apply the framework developed in the first chapter to quantify the gross bioenergy potential of the conterminous United States (U.S.) and evaluate the feasibility of current U.S. bioenergy policy, namely the Energy Independence and Security Act of 2007 (EISA). In chapter 3, I evaluate the potential for intensifying productivity on existing agricultural land by controlling for management intensity and comparing current rates of agricultural and natural productivity across long-term, global-scale climate zones.;The results of this work show that global-scale bioenergy potential has been generally overestimated by previous analyses, due to the under-representation of biophysical constraints on yield potential. Further, using EISA as a case-study, I show over-optimistic bioenergy estimates have resulted in unrealistic future bioenergy targets. Finally, I present strong evidence that agricultural productivity does not exceed natural rates of productivity, except in limited cases of intense management inputs, suggesting that humanity may be reaching a HANPP planetary boundary within the next few decades. |
