[Narrator] Majestic caribou make huge annual migrations across the Arctic, in herds which can number 300,000. They’ve been making these journeys for thousands of years, but changes in the Arctic are impacting these ancient pathways and could ultimately affect us all. [Florian] The Arctic National Wildlife Refuge is the biggest wildlife refuge in the United States. The Porcupine caribou herd migrates every year into this coastal plain and that’s where they calve, but also the place where the calves find the first, most important food. And it’s essential for their survival. [Narrator] This Garden of Eden is under threat as our planet’s changing climate causes temperatures here to rise. [Florian] The biggest issue for the caribou is warm weather events in the middle of winter when you suddenly have rain or just a strong melt, and then later on a freeze cycle, so then the caribou can’t get to their food. Then also in springtime, when you suddenly have a warm spell, so much of that snow melts quickly and the rivers then rise rapidly. And when the caribou are migrating with the calves and need to cross those rivers, a lot of the calves don’t make it. [Narrator] The rising temperatures here aren’t just affecting the caribou and the ecosystem they rely on. They’re also fundamentally changing landscapes across our planet’s frozen north. [Katey] When you see a drunken forest, where the trees are tilting every which way, that’s an obvious sign that the permafrost here is thawing. Permafrost is any ground that’s been frozen for at least two consecutive years. Often it’s been frozen for hundreds of thousands of years. Zero degrees is an important tipping point. If the ground is colder than zero, then any water in the ground is frozen. It’s ice. But when the temperature rises above zero, that ice melts. And that’s really important because it was the ice that was supporting the ground at a stable level. In most places around the Arctic, permafrost is warming and thawing, and the projection is this century that we could lose anywhere from a quarter of the permafrost area, up to two thirds of the permafrost area. [Narrator] Not only is melting permafrost carving up the landscape but as it thaws, it releases methane, a powerful greenhouse gas. [Katey] The frozen soils have carbon in them and that carbon is the remains of plants and animals that died some time in the past. That organic carbon that was in the soil becomes food for microbes that decompose it, and they generate carbon dioxide and methane. Methane is a greenhouse gas and when it enters into the atmosphere, it traps incoming solar radiation and it heats the surface of the Earth. So the more methane we have in the atmosphere, the warmer the Earth’s surface will get. We care about methane because it has a very strong lever on climate. It takes 30 carbon dioxides to equal the climate impact of one methane. There’s a lot of uncertainty in how much methane we think permafrost is trapping, but we think that there’s much, much more methane trapped beneath permafrost than there is in the atmosphere. [Narrator] The majority of greenhouse gases are produced by our burning of fossil fuels, to generate the energy we use. If we stand any hope of stabilising our planet’s changing climate, then we must look to clean energy sources such as wind, solar or hydroelectric. [Katey] What we need to do is take responsibility for our impacts and try to slow the speed of these changes so that ecosystems and people and cultures can adapt. The more information we have, hopefully the wiser we can become and the better decisions we make. We can all look for ways to reduce our carbon footprint, but I think one of the best things that people can do is spend time with nature and spend time with other people in nature and develop that relationship, because when they do, they’ll start to value it and that will be reflected then in the decisions… The way they spend money, the way that they vote. It will help them to value our natural resources to then protect them.
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