Dehydration and the threat to East Anglian fens, England

Abstract

The vegetation communities of East Anglian valley head fens are dependent for their water supply upon calcareous spring water. Many of these fen vegetation types are nationally localised, some are rare and all have considerable conservation importance.Many of the fens have been detrimentally influenced by drainage, and increasingly abstraction of water from the aquifer threatens their nature conservation importance directly and by exacerbating the effects of climatic drought. Changes have occurred in the species composition of a significant number of sites and in some instances this has resulted in a change in vegetation community type.The effect of drainage upon fens is longstanding and whilst this has undoubtedly caused a decrease in nature conservation interest, the spring-dependent communities have often survived. The threat of groundwater abstraction is comparatively more recent and directly threatens the springs themselves and the nationally important vegetation communities associated with them. With the exception of a few cases where intensive hydrological studies have been undertaken, it is difficult to establish the impact of groundwater abstraction upon fen water table levels. In many cases reference is made to past floristic records and the descriptions of fens to provide evidence of dehydration.Engineered measures to ameliorate the impact of water loss are often suggested but are seldom ecologically acceptable. The problem of dehydration due to water abstraction needs to be tackled strategically in the long term, though action needs to be taken over currently existing licences. The alleviation of the problem will be helped if water resource plans accommodate the water demand of those fens with a high wildlife interest.