Rick Battarbee, UCL (with Ewan Shilland)
Upland streams and lakes in the UK are, with few exceptions, located in areas of natural beauty, they contribute immensely to the recreational attraction of the uplands, they provide unique habitats for wildlife and are the source of water needed to sustain ecosystems and centres of human population downstream. Protecting and improving biodiversity and water quality in the uplands is or should be a national priority.
Until the the acid rain controversy of the 1980s there had been little concern over the ecological condition of upland waters in the UK. The intensive research campaigns that followed quickly demonstrated not only that many upland waters were acidified but that all were contaminated to a greater or lesser degree by atmospherically transported pollutants. Acidification caused the decline or loss of many salmonid fish populations and the replacement of acid sensitive invertebrate, plant macrophyte and algal populations by acid tolerant ones, resulting in an overall decline in biodiversity.
Today, after over 20 years of reductions in the emissions and deposition of sulphur and nitrogen compounds from fossil fuel combustion in the UK (and more generally across Europe) acidified waters are beginning to recover. Evidence from the 22 lakes and streams in the UK’s Acid Waters Monitoring Network (http://awmn.defra.gov.uk/index.php) shows an improvement in some fish populations and the appearance in recent years of a number of plant and invertebrate taxa thought to have been lost as a result of acidification. The extent of recovery, however, is still limited. This is clearly indicated at the lake sites in the AWMN where present day diatom floras still contain a greater proportion of acid tolerant taxa when compared to fossil assemblages preserved in pre-acidification sediments. Further recovery from acidification is expected to occur but it is unlikely that the composition of plant and animal communities in future will return to match those of the past as the biodiversity of upland waters faces new threats from eutrophication and climate change.
The continuance of high quality, long-term ecological monitoring designed to track the response of water quality and biodiversity to projected changes in air quality, land-use and climate remains the central priority for upland water research. The AWMN is the principle instrument that needs developing for this purpose. Although it was principally designed as a national research network to assess recovery from acidification it is increasingly providing information on the impact of additional pressures. Our priority is to enhance the network by instrumenting the sites to monitor water temperature, stream flow and lake level, enabling biodiversity responses to projected climate change to be tracked alongside changes in other pressures.