Saving the planet’s bloodstream

"WE HAVE LOTS OF WORK TO DO": Water is at the center of the planetary drama currently unfolding before our very eyes. Water not only supports ecosystem services like food and energy, it is also a critical regulator of temperature and climate on Earth.

As it flows through rivers and streams, rests in lakes and oceans, and falls as rain, water serves as the bloodstream of the biosphere. Any changes to water’s stabilizing capacity could push societies to the brink of collapse.

Despite this, humans continue to change landscapes and ecosystems to the point that water may go from being a friend to becoming a foe.

Why?

Part of the problem is that there are no global water management organizations, and consequences of human actions are not always felt at a regional level. Deforestation in one area of the world may trigger increased floods or droughts in another faraway region.

Failing to grasp the planetary consequences

Water resources management concepts and frameworks are typically designed for the local to regional scale. In three studies recently published in Water Resources Research, One Earth, and Earth’s Future, centre researcher Lan Wang-Erlandsson with colleagues argue that such existing methods and frameworks fail to grasp the planetary consequences of human interferences on the water cycle.

In their studies, Wang-Erlandsson and her colleagues illuminate the role of the water cycle for maintaining fundamental Earth system functioning, and present a roadmap for detecting, monitoring, and establishing safe global limits to water cycle modifications, and present an approach to include planetary stability in local water resource governance and management.

Towards a revised water planetary boundary

The authors believe a robust, holistic, and locally applicable framework for Earth system water governance is needed to complement existing local-regional scale water governance.

The Planetary Boundaries framework, which sets quantified boundaries to human perturbation of key Earth processes including freshwater use, is considered the most suitable framework to depart from.

This means reframing the “freshwater use planetary boundary” to a “water planetary boundary” which accounts for the importance of all five major water stores: atmospheric water, soil moisture, surface water, groundwater, and frozen water. This highlights four fundamental Earth system functions of the global water cycle: hydroclimatic, hydroecological, transport, and storage. The use of sub-boundaries could further make the water planetary boundary more measurable as well as understandable to both hydrologists and a broader public.

To succeed, Wang-Erlandsson and her colleagues urge the hydrology and water resource community to join a “Grand Challenge” in order to develop the suggested water planetary sub-boundaries.

“We are excited by our proposed new water planetary boundaries and how to quantify them over the coming years – we have lots of work to do," says lead author Tom Gleeson from University of Victoria.