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Earth's climate is changing, and by the end of the 21st century in Europe, average temperatures are likely to have risen by at least 2 °C, and more likely 4 °C with associated effects on patterns of precipitation and the frequency of extreme weather events. Attention among policy-makers is divided about how to minimise the change, how to mitigate its effects, how to maintain the natural resources on which societies depend and how to adapt human societies to the changes. Natural systems are still seen, through a long tradition of conservation management that is largely species-based, as amenable to adaptive management, and biodiversity, mostly perceived as the richness of plant and vertebrate communities, often forms a focus for planning. We argue that prediction of particular species changes will be possible only in a minority of cases but that prediction of trends in general structure and operation of four generic freshwater ecosystems (erosive rivers, depositional floodplain rivers, shallow lakes and deep lakes) in three broad zones of Europe (Mediterranean, Central and Arctic-Boreal) is practicable. Maintenance and rehabilitation of ecological structures and operations will inevitably and incidentally embrace restoration of appropriate levels of species biodiversity. Using expert judgement, based on an extensive literature, we have outlined, primarily for lay policy makers, the pristine features of these systems, their states under current human impacts, how these states are likely to alter with a warming of 2 °C to 4 °C and what might be done to mitigate this. We have avoided technical terms in the interests of communication, and although we have included full referencing as in academic papers, we have eliminated degrees of detail that could confuse broad policy-making.
This paper updates Recent Advances in the African Great Lakes: Fisheries, Biodiversity and Cichlid Evolution published by the Freshwater Biological Association in Freshwater Forum (Lowe-McConnell, 2003). Since 2003 many international teams have continued research on lakes Malawi, Victoria and Tanganyika. This review discusses the decline of the important commercial fisheries in all three lakes, together with changes in ecological and limnological conditions which the fishes now face. It also describes advances in our understanding of how the spectacular flocks of endemic cichlid species have evolved in each lake and continue to coexist.
Conservation of streams in Africa cannot be considered separately from their importance as water sources for local people. Humans and livestock interact daily with flowing water and its associated riparian vegetation, giving these landscape features social and economic importance. Despite the destruction that these activities cause, they provide opportunities for imaginative approaches to conservation. Issues focusing on resources other than water itself should be considered; for example, use of riparian vegetation for collection of medicinal herbs, firewood, timber for construction and as sites for spiritual, cultural and recreational activities. To address these concerns, Kenyan streams and their catchments are given as examples in this paper, with the assumption that they are typical of streams and catchments in many parts of Africa. These streams are used extensively for small scale abstraction, washing, livestock watering and exploitation of riparian vegetation. All of these activities occur with little regulation or management, despite the riparian zones nominally being protected government property. Effective management requires an understanding of patterns of supply and demand for water, which is seasonal, and for vegetation resources, which is continuous and increasing. Challenges for effective management are identified as: politically- and tribally-mediated insecurity; ineffective governance, particularly with respect to enforcing protective legislation; different use of resources by different ethnic groups; division of labour along gender and age lines; poverty and the inability to diversify resources; traditions and neglect of traditional ecological knowledge; and inadequate formal education. We propose that effective conservation of water and riparian resources — and therefore of essential ecosystem services — is best achieved by a combination of law enforcement and engagement of local communities with the resource upon which they depend. Understanding the importance of the resource and engendering a spirit of community ‘ownership’ will help to avoid the current ‘tragedy-of-the-commons’, in which uncontrolled exploitation is increasing in a totally unsustainable fashion in tropical Africa.
Over 100 marl lakes from the British Isles are described and compared. About 75 % of the lakes are extant with the remainder dating from the Late Glacial or Holocene and now completely filled with sediment. Most of the lakes are, or were, Chara-dominated and of glacial origin and the majority are shallow and less than 4 m deep. These lakes contain important plant and animal communities and their sediments provide a valuable fossil and geochemical record of changes since the last glaciation. Most are associated with Carboniferous Limestone, Chalk and Old Red Sandstone formations, and they are widely distributed. Their waters contain a mean dissolved calcium content of 2.79 meq L-1 (140 mg L-1 CaCO3), typical of temperate limestone groundwaters. Marl formation is closely associated with the growth of Chara but these plants are sensitive to disturbance and water pollution. Being shallow, the lakes possess rich emergent and submersed macrophyte floras, providing shelter for diverse invertebrate faunas, with the Crustacea and Mollusca well represented. They range from oligotrophic to eutrophic and several of the deeper lakes stratify during summer.
The future for many of the marl lakes in the British Isles is bleak. Being small and shallow, they are prone to siltation, particularly along the coast, and they are also threatened by sea-level rise, extreme weather events, drainage/abstraction, alien plants and animals. At least half of the lakes appear to have been affected by nutrient enrichment originating from agriculture within their catchments or human sewage and industrial effluents. Irreversible changes will almost certainly occur if nutrient enrichment is prolonged but there are no simple solutions. The review includes an annotated list of the lakes providing locations, geological setting and key references to their biology, chemistry and palaeolimnology where relevant. The lakes are also compared with those of continental Europe and the United States, and a revised definition of marl lakes is provided.