Freshwater species and their habitats are on average among the most imperiled worldwide. Because they drain surface runoff from the landscape, freshwater ecosystems - also called inland aquatic systems or wetlands - are subject to impacts from land-based activities in addition to threats like direct habitat alteration and invasive species. Although limnology and related scientific disciplines are arguably well-developed, the field of freshwater biodiversity conservation lags behind that of the terrestrial and marine realms. This article details the state of freshwater biodiversity and habitats, summarizes major threats to freshwater systems, discusses conservation challenges for freshwaters, and provides an overview of more common conservation tools and strategies.
Recent studies show that freshwater species are on average more threatened than those in the terrestrial and marine realms. This is not surprising, as proximity to water bodies has been a preference for the establishment of human settlements for millennia. Society has used rivers for transport and navigation, water supply, waste disposal, and as a source of food. As a consequence we have heavily altered waterways to fit our needs by building dams, levies, canals, and water transfers and by heavily polluting our rivers, lakes, and streams with fertilizers and pesticides, industrial discharges, and municipal waste. And while freshwater ecosystems are very resilient, with examples of species refugia found in highly altered river systems, this resiliency is finite. We know there are thresholds that, once crossed, can put entire ecosystems at risk, with severe consequences for human well-being and biodiversity.
Given the importance of freshwater ecosystems in sustaining human well-being, it is surprising how little we know about their changing condition, their dependent species, or the roles that these species play in sustaining ecological functions. Knowledge is particularly poor for lower taxonomic groups (freshwater plants and invertebrates), especially in tropical regions. Here is a summary of the current status of freshwater biodiversity, given these gaps in our knowledge.
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