The coming era of water wars, freshwater renewable capacity lagging behind humanity’s current rate of utilization,

There is a tongue-in-cheek saying in America — attributed to Mark Twain, who lived through the early phase of the California water wars — that “whiskey is for drinking and water is for fighting over.”

It highlights the consequences, even if somewhat apocryphally, as ever-scarcer water resources create a parched world. California currently is suffering under its worst drought of the modern era.

Adequate availability of water, food and energy is critical to global security. Water, the sustainer of life and livelihoods, is already the world’s most exploited natural resource.

With nature’s freshwater renewable capacity lagging behind humanity’s current rate of utilization, tomorrow’s water is being used to meet today’s need.

Consequently, the resources of shared rivers, aquifers and lakes have become the target of rival appropriation plans. Securing a larger portion of the shared water has fostered increasing competition between countries and provinces.

Efforts by some countries to turn transnational water resources into an instrument of power has encouraged a dam-building race and prompted growing calls for the United Nations to make water a key security concern.

More ominously, the struggle for water is exacerbating impacts on the earth’s ecosystems. Humanity is altering freshwater and other ecosystems more rapidly than its own scientific understanding of the implications of such change.

Degradation of water resources has resulted in aquatic ecosystems losing half of their biodiversity since just the mid-1970s. Groundwater depletion, for its part, is affecting natural streamflows, groundwater-fed wetlands and lakes, and related ecosystems.