The Peace-Athabasca Delta, Canada, a RAMSAR Wetland of International Significance, has since the 1970s been viewed as an ecosystem in decline. The putative reason for its decline has been the regulation of the Peace River by the W.A.C. Bennett Dam in British Columbia. The dying delta paradigm has its origin in a short-term study that coincided with a transient drawdown of the open drainage lakes in the delta. The paradigm has circumscribed all subsequent studies of the delta in its a priori assumption that all detected changes are due to the dam and are negative. As a result, the growth of scientific understanding has been stifled. Factors that contribute to the lack of ecological understanding include problems of data quality, quantity, and scale, ecological complexity, media marketing, failure to consult or analyze older/historical datasets, over-reliance on gray literature, too few wetland ecologists, and too little interdisciplinary thinking. Factors that may be involved in the recent changes, or lack of changes, include climatic variation and change, normal wetland dynamism, stochasticity, flow regulation, weirs, dredging, avulsions and their prevention, influxes of weeds and contaminants, delta evolution, and cultural change. The assessment of health in a delta is problematic since deltas are naturally stressed, dynamic ecosystems. Indicators of anthropogenic stress, such as declines in diversity and abundance, changes in biomass and primary production, or retrogressive succession may be difficult to apply in deltas. Long-term datasets are required that allow differentiation of normal from anthropogenic changes. Critique of the ‘dying delta’ view reveals little scientific support. The often-stated decline in flood frequency seems to have no statistical basis. The ecological health of the Peace-Athabasca Delta was assessed based on 26 attributes; 18 attributes indicated health, 3 indicated stress/disease, and 5 attributes were either neutral or required study. When compared to other major deltas in North America, the Peace-Athabasca Delta stands out as a paragon of ecosystem health. This study presents a cautionary lesson in the power of unchallenged paradigms in shaping scientific and popular opinion. A new paradigm views the delta as predominantly healthy, driven by large-scale natural processes, complex, and dynamically varying.
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