Bernie Sanders came under fire recently for comments he made in the last

Democratic presidential debate. When questioned about a previous assertion that climate change is the greatest threat to our national security, Sanders doubled down on those comments and asserted that climate change is directly related to the growth of terrorism. Sanders was later widely ridiculed by critics.

Perhaps many believed his comments were far removed from the immediate crises, the Paris attacks, the rise of ISIS, and of course the fate of Syrian refugees that ignited fierce debate throughout the country. However, the fight against terrorism is a long game, not a short one, and the question must be asked, how will climate change affect the nation’s security?

The migrant crisis in Europe is a clear example of the social disruption that can occur from a sudden influx of displaced persons. At least 750,000 refugees have poured in, mostly from the Middle East and North Africa. Many cities and towns are struggling to cope with the influx of people and the services they need.

The crisis has ignited fierce debate over the ultimate fate of the refugees and the identity of Europe itself. Anti-migrant sympathies appear to be growing in the wake of the Paris attacks and the question of whether Islam can coexist within the realm of western values is likely to be debated again and again.

But there is a migration crisis that no one is talking about, one within Syria itself and one that helped ignite the Syrian civil war. That crisis began in 2007 when the worst 3-year

drought ever recorded coupled with crop failures caused an exodus of 1.5 million rural Syrians to pour into Syrian cities. These migrants settled in cities already overburdened with unemployed Iraqi refugees.

This cauldron of poverty, crime, and desperation along with preexisting grievances helped kick start the protests that ultimately sparked the civil war.

While it cannot be stated that climate change caused the civil war, it certainly helped to spark it. But the wider point made is how changes in climate can cause mass migrations that can in turn destabilize countries or even entire regions. When climate change is viewed in that context, the ramifications are striking.

When one considers the social, economic, and potential security costs of the migrant crisis in Europe today, it is difficult to even imagine how dwarfed these costs may be in the context of future migrations caused by climate change.

A recent study found that by 2100, the temperature in much of the Middle East will be above the level in which humans can survive, effectively making wide swaths of the region uninhabitable. This comes at a time when the population is projected to nearly double from 329 million people in the year 2000 to 678 million in 2050 before slowing.

As if the situation did not seem dire enough, the Middle East is also facing the threat of a major water crisis within the next few decades. From 2003 to 2010, the Tigris and Euphrates river basin lost 117 million acre feet of stored fresh water -- almost the entire volume of water in the Dead Sea.

Furthermore, the aquifers in the Middle East are being depleted at an astonishing rate, second only to India. It is no surprise that 14 out of 33 of the countries most likely to experience water stress in 2040, according to the World Resources Institute, are in the Middle East, with nine designated as extremely stressed.

The answer is clear: if Europe cannot adequately deal with the turmoil caused by several hundred thousand Middle Eastern migrants, imagine that of millions, or even hundreds of millions of climate refugees fleeing the region. Imagine the abysmal conditions citizens of this already volatile region may be subjected to as a water crisis forces more poor farmers and herders into crowded cities. It is very easy to see how this environment can breed a new generation of terrorists.

The Middle East is just one theater of the conflicts of climate change. Aquifers around the world are dwindling while at the same time sea levels are rising. In Bangladesh, as many as 18 million people may be displaced by the rising seas. Already, 1.5 million people have moved from coastal villages to the slums of Bangladesh’s capital, Dhaka.

While the

Maldives and other low lying island nations may face complete destruction, leading to an influx of now stateless people who will have to go somewhere. Worldwide, it is estimated that around 100 million people live within 3 feet of sea level and face possible displacement.

The future of food production also appears bleak. A recent report found that due to pollution and erosion alone, the world has lost approximately one third of its arable land, land suitable for agricultural use. Some of these losses can be attributed to an increase in severe weather events or salt water intrusion as a result of climate change.

Additionally, the Intergovernmental Panel on Climate Change found that the rate of crop yields is slowing. This is particularly true of wheat, a staple grain that is highly susceptible to variations in temperature. Projections now suggest that wheat yields may decline by 2% per decade. In the most water stressed areas, yields may decline 25%.

In fact, Saudi Arabia, once a producer of grains, has now begun to import them as a result of depleting aquifers. Fish catch declines in the tropics, of which many people depend on for subsistence, are also expected to decline between 40 and 60 percent.

Stress on the food supply comes at a time when the world is estimated to require a 50% increase in the food supply by 2050 to accommodate a global population of 9 billion people. These declines will likely lead to increased food prices that could potentially destabilize nations in the developing world who will feel the bulk of the stress.

The decline of easy access to water and food, and the displacement caused by sea level rise and extreme weather events, among other impacts, will multiply threats and likely exacerbate terrorism. That is the conclusion that the Department of Defense came to in a 2014 report. The report continued:

“These developments could undermine already-fragile governments that are unable to respond effectively or challenge currently-stable governments, as well as increasing competition and tension between countries vying for limited resources. These gaps in governance can create an avenue for extremist ideologies and conditions that foster terrorism.”

The Pentagon has even gone as far as to include climate change analysis in its war games and defense planning scenarios. In addition to accessing the impact abroad, the Department of Defense has also conducted an exhaustive study on the impacts climate change may have on its own locations and equipment, including its 7,000 bases, installations. and facilities.

The military’s top brass are clearly taking the threats of climate change seriously.

While Bernie Sanders' remarks may have been seen as insensitive, or far removed from the immediate fears, they are indeed accurate in the long run. The statistics speak for themselves; the future may very well contain hordes of desperate, poverty stricken people fleeing environmental catastrophes and the ensuing unrest that follows.

Such calamities will likely exacerbate existing challenges to America’s national security and indeed create more of such challenges.

The situation in Syria, a situation itself exacerbated by climate change, may only be the prologue for what is about to come if the issue is not taken seriously by future leaders, whether one of those leaders is Senator Sanders himself or any other candidate currently running for the nation’s highest office.

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