Inland waters comprise a minute proportion (much less than one-hundredth of one percent) of the world's water resource. Despite this, they encompass a very wide range of habitat types and contain a disproportionately high fraction of the world's biodiversity.
Freshwater is also a vital resource for human survival. In consequence, inland water ecosystems are placed under many, often conflicting, pressures, with increasingly adverse consequences for their biodiversity. There are indications that, overall, a higher proportion of inland water species are in decline than marine or terrestrial forms.