Plastics. From the devastating effects of plastic pollution on our oceans, to the news that plastic bottles likely pollute the drinking water they contain, plastic pollution—the theme of this year’s Earth Day—has been a highly visible issue, and we’ve seen some notable progress on fighting the plastic battle.  

Intense drought in South Africa’s Western Cape Province has led the world-renowned city of Cape Town to the brink of “Day Zero”—the date at which residents would be forced to collect strictly rationed water supplies from shared distribution taps. Water conservation efforts have so far prevented a massive water shutdown, but the city’s rapid population growth and reliance on surface water dams makes it particularly vulnerable to lower precipitation levels. 

The Lanjiang river in Eastern Zhejiang, China, reached its peak water level of 100 feet the night of June 25, 2017. Lanxi residents remember this day as “6.25,” marking the worst flood since 1955. Elsewhere in China that month, 7.3 million people were affected by floods, landslides, and heavy rains in northwestern Sichuan Province alone. Northern Guangxi suffered direct economic losses of 2.9 billion RMB (US$460 million). In the autonomous regions, 92,000 people were relocated. Flash floods caused the deaths of 10 people and forced 76,800 people to evacuate from Shanxi Province.

In 2014, we met with some of the technical leads of a major Chinese river basin authority in Beijing and asked them whether they were more worried about pollution or climate change impacts. Both, the engineers replied. Pollution affects us every day, they said, but changes in the climate erode our ability to supply drinking and irrigation water, manage floods, and generate electricity.

China must address its environmental and climate change challenges, such as reducing water pollution and building resilience to droughts, floods, and long-term climate shifts. But existing sources of finance have not met the growing demand for environmental projects.

Cape Town is running dry. But thanks to its sophisticated water management efforts, the city may ride out the crisis. However, other cities that lack these capacities are less likely to survive Day Zero. Especially in developing countries, where urban water services are often provided by informal or illegal actors, running out of water could have dangerous ripple effects for peace and security.

Environmental stress and climate change can accelerate instability and conflict—but shared environmental problems can also be a source of cooperation and facilitate peacemaking between states. Transnational environmental problems are common threats and often cross national boundaries, requiring international cooperation to address. In turn, this cooperation can provide a good entry point for building trust and cooperation.

“The demand for water will not be linear,” said Vice Admiral Lee Gunn (USN-Ret,), currently vice chairman of the CNA Military Advisory Board, at a recent Wilson Center event on water and security. As people’s quality of life improves, “the demand for water will increase as well. And so the stresses that we already see around the world—the arguments over basin rights for water, the depletion of water in major cities around the world—we think will aggravate problems that already are beginning to manifest themselves,” he said.