Ornamental lakes - An overlooked conservation resource?

Abstract

1. Shallow lakes excavated for ornamental purposes during the 18th and 19th centuries are abundant in lowland Europe. However, relative to older man-made and/or natural lakes, these lakes may have been undervalued from the perspective of nature conservation. 2. To evaluate this idea a comparison was made between the aquatic macrophyte communities (submerged and floating-leaved vegetation) of 66 shallow, English lakes including 34 ornamental lakes and 32 flooded medieval peat workings (the Norfolk and Suffolk Broads system), the latter being widely protected by conservation legislation. 3. Some 47%, 38% and 15% of the lakes studied were phytoplankton-dominated, macrophyte-dominated or deemed too shallow (< 50 cm water depth), respectively, to support a macrophyte vegetation. A higher proportion of the ornamental lakes were macrophyte-dominated (51%) by comparison with the broads (34%). In addition, many of the ornamental lakes contained diverse plant communities including abundant populations of Characeae, a common feature of lakes in the region before the major onset of eutrophication. 4. From the perspectives of macrophyte species richness, charophyte communities and indeed 'reference condition macrophyte assemblages', many of the studied ornamental lakes can be considered to be of high conservation value. Yet, in contrast to the broads, the vast majority of ornamental lakes have little conservation protection and are rarely subject to biological monitoring and/or surveying, thus leaving them vulnerable to eutrophication and inappropriate management. This study suggests that ornamental lakes are worthy of much greater attention from conservation organizations. Copyright © 2008 John Wiley & Sons, Ltd.