Agriculture, water, and ecosystems: avoiding the costs of going too far
Fisheries, cropping, and gardening are among the many human activities supported by oodplain wetlands.
e Millennium Ecosystem Assessment concluded that a failure to tackle the decline in
ecosystem services will seriously erode efforts to reduce rural poverty and social inequity and eradicate hunger; this is a critical issue in many regions, particularly in Sub-Saharan Africa (WRI and others 2005). It is also true that continued and increasing poverty can intensify pressure on ecosystems as many of the rural poor and other vulnerable people are left with no options but to overexploit the remaining natural resource base. e result is often a vicious cycle in which environmental degradation and increased poverty are mutually reinforcing forces (Silvius and others 2003). e Millennium Ecosystem Assessment (MEA 2005c) con- cluded that interventions that led to the loss and degradation of wetlands and water resources would ultimately undermine progress toward achieving the Millennium Development Goals of reducing poverty and hunger and ensuring environmental sustainability.
Consequences and ecosystem impacts
Modifications of the landscape to increase global food production have resulted in in- creased provisioning services, but also in adverse ecological changes in many ecosystems, with concomitant loss and degradation of services (MEA 2005c). Water management has caused changes in the physical and chemical characteristics of inland and coastal aquatic ecosystems and in the quality and quantity of water, as well as direct and indirect biological changes (Finlayson and D’Cruz 2005; Agardy and Alder 2005; Vörösmarty, Lévêque, and Revenga 2005). It has also caused changes in terrestrial ecosystems through the expansion of agricultural lands and changes in water balances (Foley and others 2005).
ese changes have had negative feedback on the food and fiber production activities of
agroecosystems, for example through reductions in pollinators (Kremen, Williams, and orp 2002) and degradation of land (see chapter 15 on land) [established but incomplete]. Adverse changes have varied in intensit , and some are seemingly irreversible, or at least difficult or expensive to reverse, such as the extensive dead zones in the Gulf of Mexico and the Baltic Sea (Dybas 2005). e catastrophic collapse of coastal fisheries as a consequence of environ- mental change is another example (see chapter 12 on inland fisheries). is chapter focuses on the consequences for ecosystems of green and blue water management in agriculture while acknowledging that many other human activities also play a role. Synergistic and cumulative effects can make it extremely difficult to attribute change to a single cause (box 6.4).
Photos by C. Max Finlayson