We hear a lot of talk about threats in the presidential debates, be they from the looming menace of ISIS or new challenges like Russia’s attempts to delegitimize our coming elections. But throughout three long conversations on the fate of our nation for the next four years, there was one entire category of threats that went virtually undiscussed: Climate change and our dependence on oil.

Climate and energy policy may not seem like national security issues, but the connections are there — as a veteran of the U.S. Navy, I’ve seen some of them firsthand.

Sailing through the Persian Gulf is one way to realize the operational and strategic burden that our dependence on oil puts on the military. Other folks who work in defense see oil’s negative effect through other lenses, whether they’re driving a slow-moving tanker of highly valuable and highly flammable material across a desert in Iraq or Afghanistan, or working on the military’s budget and watching a small spike in the price per barrel of oil translate to millions of dollars lost for other programs.

The cost — in both blood and treasure — of depending on one resource is serious when it comes to the military. And no matter how much oil we produce and consume at home, oil is priced in a global market. Ultimately, that means that revenues from our dependence (including the military’s) end up funding groups and countries around the world that don’t share our values.

The limited discussion of climate change, meanwhile — beyond arguing whether or not Donald Trump claimed it was “a hoax invented by the Chinese” (which he did) — is a disservice to my brothers and sisters serving in uniform around the world, too. Stronger and more frequent extreme weather events are a direct result of climate change, and on average, the U.S. military gets a request for humanitarian assistance in the wake of just these kinds of disasters once every two weeks.

Moreover, the Pentagon has been calling climate change a “threat multiplier” for years because the other effects of climate change — including fewer resources and faster migration to overcrowded cities — are drivers for the extremism that we fight around the world. Climate change hits vulnerable communities with weak governments the hardest, and terrorist groups are waiting to recruit those who are displaced and in despair. And that, of course, means more hard work for the military in the long run.

There’s an answer to all of this, and it was only briefly addressed by Secretary Hillary Clinton: renewable energy. Renewables are how we get away from burning oil and other fossil fuels, at once solving the dependency problem and stopping the emission of climate change-inducing greenhouse gases. And the best part is that they’re already working for the U.S. military — we’ve seen biofuels powering next generation fighter aircraft and naval warships, and solar-powered backpacks and generators serving soldiers and Marines in active combat zones.

There’s a lot to talk about in this election, including basic questions about what it means to be fit to lead our country and which direction it should go in. Those are important conversations that we all need to be having, but we can’t forget the more traditional, long-term questions about how to keep our country safe and prosperous.

As a veteran, I’m eager to hear more from both candidates about their plans for renewable energy — because we can’t afford to ignore the threats of climate change and oil dependence any longer.