The sources and distribution of anthropogenic nitrogen (N), including N fertilization and N fixed during fossil-fuel combustion, are rapidly becoming globally distributed. Responses of terrestrial ecosystems to anthropogenic N inputs are likely to vary geographically. In the temperate zone, long-term N inputs can lead to increases in plant growth and also can result in over-enrichment with N, eventually leading to increased losses of N via solution leaching and trace-gas emissions, and in some cases, to changes in species composition and to ecosystem decline. However, not all ecosystems respond to N deposition similarly; their response depends on factors such as successional state, ecosystem type, N demand or retention capacity, land-use history, soils, topography, climate, and the rate, timing, and type of N deposition. We point to some of the conditions under which anthropogenic impacts can be significant, some of the factors that control variations in response, and some areas where uncertainty is large due to limited information.

Kosrae, Federated States of Micronesia, is a prototype of an island economy prone to economic crowding. Average family size is large, the habitable land area is small, economic activity is limited, and household dependence on natural resources for fuel and food is high. We analyze how economic crowding - and its mitigation through trade and migration policies - affects mangrove resource use. A comparison of household survey data from 1996 and 2000 indicates that despite decreases in US aid and public-sector jobs, average household consumption of mangrove resources has not increased. Migration and remittances have allowed the purchase of imported fuel and building materials substituting for mangrove wood. Despite changing preferences and shifts toward import consumption, population growth and further declines in US financial support will likely cause aggregate demand for mangrove and upland wood to rise. Moreover, continued emigration may accelerate the export of mangrove crabs to off-island Kosraeans.

The Evolving Sphere of Food Security seeks to answer two important questions: How do the priorities and challenges of achieving food security change over time as countries develop economically? And how do the policies used to promote food security in one country affect nutrition, food access, natural resources, and national security in other countries? The volume presents the many faces and facets of food security—their symptoms, their roots, and their possible remedies—through the lens of a multidisciplinary group of scholars. The authors share personal stories of research and policy advising from their field experiences to provide readers with a real-world sense of the opportunities and challenges involved in promoting food security at local to global scales. Their observations from countries around the world demonstrate how food security is tied to security of many other kinds: energy, water, health, climate, the environment, and national security. The book’s main goal is to connect these areas in a way that tells an integrated story about human lives, resource use, and the policy process—a story about global food security.