Agriculture, water, and ecosystems: avoiding the costs of going too far
Human society depends on an array of services provided by ecosystems, including agro- ecosystems. However, agriculture has resulted in the serious degradation of the compo- nents and processes of many other ecosystems, including processes that are essential for food production. ese include:
River depletion and consequent degradation of downstream aquatic ecosystems, in- cluding effects on groundwater and fisheries.
Drainage of wetlands and runoff or discharge of wastewater to surface water– and groundwater-dependent ecosystems.
Groundwater depletion by overexploitation for irrigation, causing damage to ground- water-dependent ecosystems.
Land degradation and alterations of local to regional climate from land-use changes.
Pollution from overuse of nutrients and agrochemicals, with consequences for terres- trial and aquatic ecosystems and for human health because of water pollution.
A worsening of water pollution problems by river depletion, decreasing possible river dilution, as illustrated in the tributaries to the Aral Sea and in the severe health prob- lems caused to downstream populations.
ere are four ways to respond to these adverse impacts:
By rehabilitating lost or degraded ecosystems and ecological processes.
By improving agricultural practices using existing and improved technology.
By ensuring more careful forward planning that includes conscious striking of trade- offs between water for food production and for other ecosystem services and dealing with uncertainty.
By addressing the underlying social issues and divisions that affect how decisions are made in many communities, especially within poor rural communities that often disproportionately suffer the effects of environmental degradation. It is also essential that unknown, poorly understood, or uncertain phenomena be
brought into these tradeoffs. e social context for addressing these issues can be important, especially when such issues as culture, gender, health, and education come to the fore.
Where ecosystem degradation has not progressed too far, it may be possible to re- habilitate ecosystems, for instance, to reduce severe eutrophication of lakes and coastal waters or important wetlands and to secure, by reallocation, enough residual stream flow to restore environmental flows that support downstream ecosystems and ecosystem ser- vices. More essential are actions that focus on preventing further degradation and loss of important ecosystems.
Because food production will have to increase to alleviate undernutrition and to feed a projected 50% increase in the world population (before it stabilizes by the middle of the present century), many challenges remain for land and water managers. e type of responses available will differ depending on whether the effects of particular instances of ecosystem degradation are avoidable or unavoidable. Avoidable effects can be minimized largely through concerted responses, while unavoidable effects have to be considered when striking tradeoffs.
A more cautious approach toward water management and food production will be essential to ensure social and ecological sustainability