AGADEZ, Niger — The world dismisses them as economic migrants. The law treats them as criminals who show up at a nation’s borders uninvited. Prayers alone protect them on the journey across the merciless Sahara.

A roughly three-foot increase in sea level will threaten 128 coastal military installations in the United States, valued at $100 billion, according to a study from the Union of Concerned Scientists. The report, The U.S. Military on the Front Lines of Rising Seas, argues that the growing exposure to storm surge and sea-level rise puts vital infrastructure, training and testing grounds, and housing for thousands of personnel at risk.

As global climate change affects livelihoods across the world, migration patterns are also changing. In a recent study published in Global Environmental Change, Clark Gray, Valerie Mueller, and I found that since the 1970s, climatic variations have been increasing internal migration across many South American countries, with few exceptions. And many people are headed to cities.

Environmental security? Climate security? How about planetary security. Last week at the venerable Peace Palace in The Hague, nearly 300 experts from around the world met for the somewhat dramatically named Planetary Security Conference, a new initiative aimed at bringing together people working on all things related to the environment, climate change, and their security implications.

“Before the famine my life was better. I was a man in my own country,” Abdi Abdullahi Hussein, a Somali refugee living in Kenya, tells The Climate Reality Project. “When you have livestock and a farm and it all disappears, it feels like falling off a cliff.”

Eddah Senetoi lives with her son in the small pastoralist community of Elangata Waus. They keep cows, goats, sheep, and donkeys to buy food and pay school fees. For her and other pastoralists living in southern Kenya’s Kajiado County, climate change is compounding challenges from land subdivision and privatization, and magnifying social tensions and community conflicts over access to resources.

Last month, headlines around the world heralded a breakthrough for international environmental cooperation. During ongoing ozone treaty negotiations in Rwanda, China broke with the developing world, agreeing with the United States to aggressively phase out hydrofluorocarbons, a significant global warming pollutant found in refrigerators and air conditioners. These changes are expected to make a big difference in combating climate change, mitigating half a Celsius degree of warming.

Record levels of displacement and accelerating climate change have prompted many to wonder if the world is headed toward a more violent future. The nexus of climate change, migration, and conflict is posing fundamental challenges to societies. But not always in the ways you might think. In a new report prepared for the U.S. Agency of International Development, Lauren Herzer Risi and I present a small guide to this controversial and consequential nexus of global trends.