At the second Democratic debate, one day after the attacks in Paris, Bernie Sanders stated “climate change is directly related to the growth of terrorism.”

Conservatives scoffed that people don’t flee their homes because of an extra-hot summer. However, a closer look reveals some truth to this brief statement. Links between climate change and political turmoil in the Middle East have been suggested for years. Only in the past year have political figures such as Barack Obama, Prince Charles and now Sanders brought this issue into the mainstream conversation.

To discover what Sanders meant, let’s start by ascertaining ‘status-quo’ climate conditions. The Middle East and Northern Africa (MENA) is the driest region in the world. Control of major water sources have contributed to regional tensions over this scarce resource — the region contains 5 percent of the world population with access to 1 percent of drinkable water. That ratio is about to grow.

For at least two decades, climate scientists have been warning us about desertification — the spread of uninhabitable desert because of increased droughts and unsustainable agricultural practices. More specifically, recent studies have predicted the region will uninhabitable by 2100 due to climate change.

Additionally, the MENA population has doubled from 1970 to 2005, placing further strain on water allocation. Oil-rich MENA countries have recently built desalination plants and bought arable land in African countries, which could begin a series of other negative consequences. And not all countries can afford these measures.

So how do these conditions contribute to political unrest? Lower levels of precipitation during drought decreases available water, decreasing arable land and creating tensions from soaring food prices and loss of agricultural jobs.

The start of the Syrian Civil War is a perfect example. The worst drought on record, lasting from 2006 to 2011, led farmers to move to cities where work is scarce and resources were limited due to a 300 percent population increase in Iraqi refugees. Combined with the brutality of Bashar al-Assad’s regime, it created a “perfect storm” for political unrest. Finally, the lapse in governance from civil war creates an avenue for terrorist organizations, such as ISIS, to establish themselves within the country.

More generally, a study in Africa focusing on conflicts between 1980 and 2002 found a correlation between 1°C temperature rise and the occurrence of a civil war. Why? Crops are less prolific even if rainfall stays the same. Farmers are then out of work and rural incomes fall, leading the rural population to take up arms — literally fighting for something to eat.

Even the Department of Defense believes climate change exacerbates the problem, calling it a “threat-multiplier.” (pdf) So Bernie’s statement has credibility — terrorism arises from many factors that need to be addressed if we hope to eradicate it.

As the Climate Summit in Paris proceeds, we will all be waiting for an agreement not only to slow climate change but also to decrease terrorism associated with its consequences.

Alyson Hoffman, from Elizabethtown, Pennsylvania, is a graduate student studying biochemistry at Duke.