For human societies, climate change manifests itself primarily through changes in water – increased intensity, frequency and variability of droughts, floods and storms, and a warming and rising ocean. The security implications of climate change are also primarily about water. Preparing for, and responding to, the water events listed above are increasingly becoming the domain of security planners today, charged with assessing credible risks to national security, and developing plans to mitigate those risks.

Freshwater constitutes only around three percent of the Earth’s water, less than one percent of which is actually available for use (the rest is locked up in glaciers and inaccessible groundwater). Yet, there are around 263 known trans-boundary water basins in the world (and likely some that have yet to be mapped), which are shared between at least 145 nations. That’s a small amount of water, but a large and growing number of people and nations that need it. Climate change places an added stress on this critical resource problem.

As the world’s oceans warm and sea levels rise, new land and seabed claims arise between nations, coastlines and some entire nations are threatened, fish stocks are compromised as fish seek colder waters (causing international tensions in places like the South China Sea), and sea water penetrates freshwater basins, thereby diminishing an already stressed supply.

These challenges open the door to opportunities for cooperation, whether it be sharing trans-boundary water resources, making existing water-sharing agreements more resilient to climate change, or conducting joint search and rescue operations in an ice-free Arctic. But climate change could also create the possibility of increased conflict, exacerbating existing water vulnerabilities, and setting nations and people on edge.

The challenge will be to develop climate-resilient water policies that encourage cooperation, and not conflict.