The changing landscape: ecosystem responses to urbanization and pollution across climatic and societal gradients

www.frontiersinecology.org © The Ecological Society of America B climate, land use – and its manifestation as land-cover change and pollution loading – is the major factor altering the structure, function, and dynamics of Earth’s terrestrial and aquatic ecosystems. Urbanization, in particular, fundamentally alters both biotic and abiotic ecosystem properties within, surrounding, and even at great distances from urban areas (Grimm et al. 2008). Around the world, rates of land change will increase greatly over the next 20–50 years, as human populations continue to grow and migrate (Alig et al. 2004; Theobald 2005). The nature, pattern, pace, and ecological and societal consequences of land change will vary on all spatial scales as a result of spatial variation in human preferences, economic and political pressures, and environmental sensitivities (Carpenter et al. 2007). To respond, we must determine how variables influence land change and ecosystem properties at multiple interacting scales, and understand feedbacks to human behavior. Human social and economic activities drive land change at all scales, and may enhance or hinder the movement of materials via wind, water, and biological and social vectors, sometimes in surprising ways that cut across scales (Kareiva et al. 2007; Peters et al. [2008] in this issue). For example, individual human decisions can influence regional dynamics within a continent when many people respond similarly to the same economic or climatic driver; the Dust Bowl in the North American prairies during the 1930s is a historical example of such cumulative effects (Peters et al. 2004). Individual decisions can also influence broad-scale land-change dynamics on other continents; for example, a switch to soybean production in South America is being driven by market demand from China. In turn, the changes wrought by humans produce ecosystem dynamics that feed back to influence resource availability and human well-being. Human responses may ameliorate or exacerbate these effects. Thus, there are complex interactions and feedbacks between the direct manifestations of human activCONNECTIVITY CONNECTIVITY CONNECTIVITY