The Effects of Agricultural Irrigation on Wetland Ecosystems in Developing Countries: A Literature Review

Abstract

"The purpose of this review was to evaluate the extent to which the current scientific literature allows us to determine and quantify the ecological costs and benefits of irrigated agriculture in wetland ecosystems of the developing countries, and to establish quantitative relationships between anthropogenic activities and ecological responses. The following are the main points that emerged: • Irrigation or activities associated with agricultural irrigation can and do cause adverse impacts to wetland ecological resources ranging from localized and subtle, to long-distance and severe. • Irrigation or activities associated with irrigation can also result in the creation or enhancement of important wetland ecological resources. • Depending on the irrigation activity and scale, irrigated agriculture and ecological resources can sustainably coexist. • The confounding effects of 'natural' or other anthropogenic stressors are not often evaluated when the effects of irrigation on wetlands are being assessed, and it can be difficult to partition the effects due to irrigation. • The potential long-term ecological benefits of water storage schemes are rarely investigated. Any measurement of impact usually stops once the project is implemented. • Because of the above (bullets 4 and 5), 'quantitative' information on the relationships between irrigated agricultural activity and ecological effects is sparse to non-existent. This severely impairs our ability to learn from previous failures or successes and, importantly, to design future activities and projects so as to minimize environmental impacts. • If we are to minimize the potential for ecological injury and enhance the likelihood of benefits in future projects, it is crucial that the existing data base be enormously expanded. Specifically, we need to treat each new project and scheme as a 'natural experiment' where the ecological resources and effects are quantified from before the project is implemented until long after implementation. Until this is accomplished, we run the risk of repeating the same mistakes that have been made in the past."