Conservation of pond systems: a case study of intractability, Brown Moss, UK.
Brown Moss is a Site of Special Scientific Interest in north-west England, of significance because of the occurrence, at least in the past, of the rare plant Luronium natans (Linnaeus) on the one hand, and its public popularity on the other. It is also a part of Ramsar site that comprises several other water bodies, the Meres, collectively valued for their water birds. It includes several fishless pools, in an area of semi-natural vegetation, that differ in character. Such features are favoured in pond conservation. The surrounding terrestrial vegetation reflects nutrient enrichment in the past century and the pools at Brown Moss are now hypereutrophic from intensive agriculture on the margins of the site and guanotrophication of the main, central pool. Feral Canada geese (Branta canadensis (Linnaeus)) and resident waterfowl, encouraged by feeding by the public, have had major effects. Lower total phosphorus concentrations but higher nitrate concentrations were found in marginal pools, too small for bird flighting. Sedimentary studies suggest that nutrients and productivity in the pools have increased. Raised phosphorus in sediments was significantly correlated with numbers of sedimentary diatoms. Ponds are potentially of major importance in freshwater conservation in the UK, as they contain a high proportion of the country's freshwater biodiversity, but many have been filled in or severely polluted by farm wastes. Their situation in intensively used agricultural land means that, as in this case study, solution of their problems may often be intractable. The intractability is amplified at Brown Moss by the difficulty of removing aggressive alien species, a common problem in UK pond systems, and by bird-feeding, again a widespread problem particularly in urban ponds. The difficulties at Brown Moss thus typify the problems of pond conservation in the UK and indeed throughout lowland Europe. Current legislation appears impotent to remedy the situation.