By Kitson Jazynka

In honor of International Polar Bear Day, National Geographic spoke with Steven Amstrup, who has been studying polar bears in the wild for 35 years.

“I couldn’t imagine a more interesting or captivating species to study—giant white bears roaming around in an environment that looks like the surface of the moon,” says Amstrup, chief scientist for Polar Bears International.

Although polar bears remain the top predator in the Arctic, their vital hunting platform is at risk. The Arctic’s sea ice habitat is changing “more profoundly than I could have ever imagined,” he says, which in turn affects polar bear populations. “On a global level, polar bears represent a challenge that we might all face one day, if we don’t stop the rise of global temperatures.”

Addressing the climate change issues facing polar bears, he believes, will ultimately benefit people, too. “The good news is that if we act in time to save polar bears,” Amstrup says, “I believe we can save the world.”

National Geographic talked to Amstrup about the issues facing polar bears in the Arctic.

What’s the origin of International Polar Bear Day?

The celebration was an idea conceived 11 years ago by Polar Bears International (PBI) to have a day in the late winter when we could encourage people to think about the challenges polar bears and other Arctic animals face in a warming environment.

We want to encourage people to reduce their output of CO 2 and other greenhouse gases to increase the chances of survival of this vulnerable species and its fragile ecosystem.

Why is the sea ice environment so critical for polar bears?

Polar bears spend almost their entire lifecycles on the surface of the sea ice. They very seldom, at least historically, come on land across most of their range.

For polar bears, melting sea ice means less access to their food. The loss of sea ice negatively impacts polar bears’ energy balance. They only have access to their seal prey from the surface of the ice because polar bears aren’t good enough swimmers to catch seals in open water. And these particular ice-loving seals rarely come ashore.

If the sea ice is gone or has a shorter season each winter, polar bears spend more time being food deprived and must live off stored body fat for longer periods. There is a limit to how long they can do this.

How do you think the average citizen can help save polar bears?

The critical thing is to reduce carbon emissions. On Polar Bear Day we encourage people to take action by joining our Thermostat Challenge—turning thermostats down in winter and up in summer.

About half of our CO 2 output comes from heating and cooling buildings. For every degree a household lowers its thermostat setting, it can save up to 3 percent in energy costs. That also means a three percent savings in CO 2 emissions. If we really want to save polar bears, however, we need to scale up those savings. This means leadership from the highest policy levels that will require transition to sustainable energy sources, assuring we all are minimizing our carbon footprints.

Walking, riding bikes, and using more mass transit instead of driving also help reduce emissions.

How do you think the challenges facing polar bears affect people?

Continually rising temperatures means the same thing for people. Look at the impact of drought on food production in Africa, the Middle East, and other highly populated parts of the world.

On our current CO 2 emissions path, average summer temperatures at the end of this century will be hotter than any summer temperatures ever experienced. Hotter temperatures will lead to greater food insecurity as growing crops and raising livestock becomes more difficult. Because polar bears depend on a habitat that melts when temperatures rise, they are an early warning of the problems posed by global warming.

How does carbon affect the planet?

The vast majority of energy that we derive in this country is from fossil fuels. When we burn fossil fuels, like coal, we oxidize their stored carbon to release energy, which becomes electricity or powers our cars. In the course of releasing the energy from which we benefit, the carbon combines with oxygen to produce CO 2 .

CO 2 stays in the atmosphere for thousands of years, so more emissions mean higher concentrations. There may be some uncertainty about how fast the world will warm, but it is certain the world will warm as long as CO 2 levels rise.

What are your thoughts on the recent global conservation strategy developed for polar bears?

The five nations that have polar bears—Norway, Canada, Greenland, the Russian Federation, and the United States—long have had their own research and management programs. These national plans historically have addressed things like the impacts of oil and gas development, hunting, and other human interactions. The Circumpolar Action Plan, completed last year, is an attempt to align the efforts of all five nations to the global benefit of polar bears.

The best recent news for polar bears is that during the climate meetings in Paris, nearly 200 nations established a goal of limiting temperature rise to two degrees or less. Although the path to achieving that goal was not established, recent studies show it is achievable. In doing so, we can save polar bears and preserve a better future for all life on earth.

This interview has been edited and condensed.

Kitson Jazynka is a freelance writer. Follow her on Twitter @KitsonJ.