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Inland aquatic systems connect headwater systems of streams and ponds to rivers and lakes downstream, transporting sediment, nutrients, biota and contaminants. In this web focus, we present a collection of articles and opinion pieces from Nature Geoscience about inland aquatic systems; the hydrological, chemical and biological functions they provide to ecosystems; their influence on biogeochemical cycles and the threats they face due to human demands and climate change.
The world's inland waters are under siege. A system-level view of watersheds is needed to inform both our scientific understanding and management decisions for these precious resources.
Debate rages over which water bodies in the US are protected under federal law by the Clean Water Act. Science shows that isolated wetlands and headwater systems provide essential downstream services, but convincing politicians is another matter.
Quality requirements for water differ by intended use. Sustainable management of water resources for different uses will not only need to account for demand in water quantity, but also for water temperature and salinity, nutrient levels and other pollutants.
Satellite measurements indicate that Greenland's meltwater rivers are exporting one billion tons of sediment annually, a process that is controlled by the sliding rate of glaciers. This rate is nearly 10% of the fluvial sediment discharge to the ocean.
Phosphorus loading can cause eutrophication of lakes. Analyses of lake chemistry in China reveal that policies have led to lower phosphorus levels overall, but increasing trends in some lakes suggest that expanded policies may be needed.
The terrestrial water cycle is often assessed annually at catchment scale. But water stored in catchments is poorly mixed, and at timescales often well beyond the calculation of annual water balance.
Climate change is causing widespread permafrost thaw in the Arctic. Measurements at 33 Arctic lakes show that old carbon from thawing permafrost is being emitted as methane, though emission rates have not changed during the past 60 years.