FIGURE 2.2 Map of Earth with the locations of major biodiversity hotspots in red (Myers et al., 2000), the latitudinal biodiversity gradients for mammals, amphibians, and threatened bird species (MEA, 2005), and cities with populations greater than 1 million (UN, 2009). SOURCE: Adapted from Myers et al. (2000); MEA (2005); and UN (2009). Used with permission of Island Press, Washington, D.C.

FIGURE 2.2 Map of Earth with the locations of major biodiversity hotspots in red (Myers et al., 2000), the latitudinal biodiversity gradients for mammals, amphibians, and threatened bird species (MEA, 2005), and cities with populations greater than 1 million (UN, 2009). SOURCE: Adapted from Myers et al. (2000); MEA (2005); and UN (2009). Used with permission of Island Press, Washington, D.C.

Geographical scientists have demonstrated that both biophysical and sociocultural dimensions are central to the causes and consequences of land-cover and landuse change, and they have advanced understanding of how human circumstances (e.g., social marginalization) and associated processes (e.g., policy changes) affect biodiversity or ecosystem loss. This has resulted in the development of the emerging interdisciplinary field of land change science (LCS), the goal of which is to develop integrated explanations of land change (Turner et al., 2007). The Global Land Project of the International Geosphere-Biosphere Programme represents an international effort to understand the interacting drivers, patterns, and impacts of such changes.

An exposition of the aims of LCS and insights into the role of the geographical sciences is provided by a recent special feature on the topic in Proceedings of the National Academy of Sciences (Turner et al., 2007). In one study particularly representative of the spatial and integrative nature of the geographical sciences, Irwin and Bockstael (2007) use geographical pattern metrics of land-use change in Maryland from 1973 to 2000 to document the spread of urban development and the resulting fragmentation of habitat (Figure 2.3). They drew three conclusions. First, contrary to earlier work on national patterns, urban growth is an ongoing phenomenon and is being underestimated in other studies because of insufficient attention to increasing low-density exurban development. Second, the increasing growth is often peripheral and low density and is leading to increased habitat fragmentation and loss. Third, the environmentally sensitive Chesapeake Bay region is actually experiencing increased development because of its commercial and recreational amenity value. The movement of people to economically and environmentally attractive urban areas causes habitat loss and fragmentation, but much remains to be done to assess the precise impacts of these demographic shifts on ecosystems and biodiversity. It follows that an important question for the geographical sciences, environmental sciences, sociology, economics, and environmental ethics is how to manage the growing



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