2024-07-23 22:00:00
Continental freshwater represents only about 3% of the terrestrial water volume and, of this, only 0.3% is surface water in liquid form. Lakes are the main reservoir (between 80 and 90%), distributed in a few hundred million units. Although this lake water is very scarce and its distribution on the globe very fragmented, lakes represent a key element in the terrestrial environment and human development.
Lake ecosystems are indeed places of biodiversity and varied uses, important for human societies. Over the centuries, lakes have been in turn borders or links, places of human development on their banks, places of fish resources*, drinking water, then tourism. It is only recently that the development of limnology* has made it possible to identify the functioning of lake ecosystems, then the ecological mechanisms that lead to their degradation (the founder of this discipline is François-Alphonse Forel, 1841-1912). It is now well documented that human activities push most of these ecosystems beyond their ecological carrying capacities, that is to say their natural possibilities to absorb disturbances and support uses.
The UN Environment Programme (unep.org) has identified five main factors underlying the nature crisis: changes in land and sea use, climate change, pollution, intensive exploitation of natural resources and invasive species. Lakes are subject to these pressures (apart from that of marine exploitation) and, given their small volume compared to oceans or continental surfaces, are particularly sensitive to them, so much so that they are often considered as “sentinels” of the state of the environment. The implementation of remedial actions requires knowledge of the ecology of these apparently closed systems, but in fact open to their environment via their watershed and the atmosphere.
This article aims to provide the essential elements for understanding the functioning of lake ecosystems, particularly under the effect of anthropogenic pressures. In view of the degradation recorded on most lakes worldwide, this article presents a brief summary of the means and tools for ecological restoration, based on concrete cases.
* a glossary of important terms and expressions in the article is presented in § 6.
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