However, less than one percent of the Earth’s fresh water flows freely, and burgeoning human populations are making unsustainable demands on this vital resource. Demand for fresh water is already outstripping supply in many regions around the world.

Both biodiversity and human communities are at risk: an estimated one out of every six people on Earth has no access to clean drinking water; two out of six people lack adequate sanitation; and four out of six are afflicted by water-borne illnesses.

FEATURE: Water in the Sacred Mountain

The degradation and decline of freshwater resources is now far too prevalent to be ignored. With the human population expected to increase to 9 billion by 2050, and with much of that growth happening in developing countries, the global freshwater crisis is only going to get worse.

What Nature Provides

Water is vital for more than direct human health: water also sustains freshwater ecosystems, which in turn provide food and livelihoods for millions. The ecosystem services provided by freshwater systems, including fisheries, filtration, and flood regulation, have global economic value estimated at trillions of dollars annually.

Nearly 70 percent of all freshwater used by people is for agricultural purposes. We have also come to rely on steady water flows for a significant portion of the world’s energy generation. Increasing infrastructure, agricultural development and demands on our drinking water and sanitation systems are drying our underground aquifers, polluting our sources of clean water, and diverting water away from where it is needed to replenish freshwater stocks as well as maintain healthy freshwater ecosystems.

READ MORE: In the Cardamoms: Life Downstream

Climate change represents another formidable threat, resulting in too much water in some places, and not enough in others. Freshwater systems have aesthetic and recreational value as well.

Exploring Freshwater Ecosystems

A remarkable array of biodiversity shares this limited supply of clean, fresh water with humanity. Freshwater ecosystems support unparalleled concentrations of species, yet they are among the most imperiled ecosystems on Earth, with extinction rates as high as 15 times greater than in the marine realm.

This makes freshwater ecosystems and the biodiversity they support a global conservation priority.

CI’s five-year vision is to work with existing and new partners to set global, science-based priorities for freshwater conservation, implement management and protection of key resources to benefit both human communities and freshwater biodiversity, and promote innovative policies for governments and markets.

EXPEDITION: Follow our scientists' trip to study the freshwater habitats of Cambodia.