Water and values: ecological research as the basis for water management and nature management

Over the past 50 years ecology has developed into a mature branch of the natural sciences, comprising firm concepts (e.g. for rivers River Continuum Concept and Flood Pulse Concept) and extensive empirical surveys (sophisticated lab and field experiments, simulation models, GIS). Estuaries and rivers are continuously threatened ecosystems, considering the massive expansion of man's economic activities. I focus on rivers and estuaries in the Netherlands (W. Europe), where recent public interest has mainly been determined by two flooding disasters (mega-disaster in 1953; near-disaster in 1995). The measures taken to enhance the safety of the human population were adequate: building of large closure dams, and storm surge barriers in the estuaries, and heightening of levees along the rivers. Eventually these measures were detrimental for what was left of the dynamic river ecosystems from the past. This paper focuses on two ecosystem studies. (1) An ecosystem study in Grevelingen lagoon, a large embanked estuary that changed into a brackish water lagoon. Predictive ecological models (e.g. for the wax and wane of Eelgrass, Zostera marina) were inadequate because of the exceptional characteristics of the lagoon: the ecosystem appeared to be instable, and not resilient. (2) An ecosystem study at Afferdensche and Deestsche Waarden, a floodplain area along the river Waal, strongly affected by toxicants deposited before 1980. We studied the functioning and eco-toxicology of floodplain food webs, deteriorated by pollutants. Fine-tuned spatial components were introduced in ecological risk assessment models of several trophic levels (e.g. a top predator, the Little Owl, Athena noctua). Safety for the human population, living below sea level, and below the level of the main rivers, must be improved, but overhasty technocratic measures deteriorating the remaining semi-natural, highly appreciated landscapes, should be avoided. Stakeholder interests must be adapted to sustainable ecological river management, and not the other way round, as has been done for the past ten centuries.