Why Freshwater Biodiversity Is Declining Faster Than Other Biomes
Context: Freshwaters occupy less than 1% of Earth’s surface yet support roughly 10% of described animal species and disproportionate ecosystem services. Findings: Evidence from assessments shows that rivers, lakes, wetlands and aquifers are losing populations and ecological functions faster than terrestrial or marine systems. Drivers are cumulative: flow regulation by dams, water abstraction, floodplain disconnection, pollution, invasive species, overharvest, land-use change and warming interact along whole catchments. Longitudinal connectivity makes rivers efficient conveyors of stress, while many freshwater organisms have small ranges and limited dispersal. Losses are severe among migratory fishes, mussels, amphibians and large river fauna, with monitored freshwater vertebrate populations declining by about 83% since 1970. Implications: Reversing decline requires basin-scale governance, environmental flows, pollution prevention, barrier removal or redesign, wetland restoration, protected free-flowing rivers and inclusion of Indigenous and local knowledge. Freshwater recovery is possible, but only if conservation treats water, species and catchments as system.
Introduction
Freshwater ecosystems are small in area but unusually large in biological importance. Rivers, lakes, wetlands, floodplains, springs and aquifers cover less than 1% of Earth’s surface, yet they support a large share of global diversity, including roughly one tenth of described animal species and about one third of vertebrate species [1], [7]. Rivers are also living infrastructure: they move sediment, recharge floodplains, cycle nutrients, sustain fisheries, dilute wastes and connect mountain, inland and coastal ecosystems [1], [3].
Despite this importance, freshwater biodiversity is declining more rapidly than biodiversity in terrestrial or marine realms by several widely…
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