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Melissa Harris-Perry: Welcome back to The Takeaway, I'm Melissa Harris-Perry.

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Kristin Laidre: Polar bears are the largest bear in the world. They can swim for days. A female polar bear will fast meaning not eat for up to eight months between the time she enters her maternity den and emerges with cubs.

Melissa Harris-Perry: This is Kristin Laidre, as the principal researcher for the Polar Science Center at the University of Washington, she's been in the field tracking, tranquillizing, probing and researching polar bear populations in Greenland for over a decade.

Kristin Laidre: Polar bears are basically serial killers at any opportunity, any seal they see, they go for it.

Melissa Harris-Perry: Now about that, it has long been feared the polar bears are among the species particularly threatened by climate change. That's because, well, they hunt or as Laidre put it, they are seal serial killers. Seals tend to hang out on sea ice. What happens when with a warming planet, the sea ice melts and disappears faster and faster, and there are fewer and fewer seals to hunt? I talked with Kristin about her newest research paper, which recently made headlines for what it may and may not tell us about polar bears and climate change, and to asked her to explain why polar bears have become such a symbol of climate change.

Kristin Laidre: We're seeing extensive loss of sea ice in the Arctic with climate warming, and that is a threat to all polar bears. Without sea ice, you really don't have a polar bear. The reason they need that sea ice is they hunt seals that live on the ice and they basically live off of a diet of fat or blubber from these animals to be able to survive in such a cold environment.

As sea ice declines, this decreases survival for polar bears. It affects their reproduction, it affects their body condition, their ability to have cubs and raise cubs. Part of the reason they've become such a symbol is they've been largely like an early warning system. Polar bears are showing us that as we continue to warm this globe, there will be repercussions.

Melissa Harris-Perry: Polar bears in this case are canaries?

Kristin Laidre: Yes, that's one way to say it.

Melissa Harris-Perry: Are you out there on the sea ice looking for the polar bears? Are the polar bears wearing radio trackers? What's the methodology?

Kristin Laidre: We're studying animals that range over huge areas, hundreds and hundreds of miles. We have a helicopter and we fly out over the sea ice or the frozen ocean. We basically start to search for bears. We spot them one of two ways. If you're lucky, you can actually see a small yellow dot on the sea ice and after a while, you realize that's a polar bear. Then we also track them. We will see their footprints in the snow and we follow those footprints from the air until we find a bear.

Once we find a bear, we do one of two things. One method is to actually capture the animal. We shoot a dart into the rump of the barrel, which is basically a mobilization agent and a sedative. The animal will basically fall asleep on the sea ice, then we land our helicopter on the sea ice and we can get out. Then we can basically be right up and personal with the bear taking a suite of samples, we collect fat and blood. Then we'll weigh the bear, and basically, get a health assessment of the animal.

In the case where we cannot capture the animal safely, either for the bear or for us, we will take what's called a remote biopsy. It's essentially the same thing. We have a different type of gun that we can shoot a small dart and it just grabs the smallest piece of skin and hair and pops off the bear. The dart lands on the ice, and then we pick that up and that gives us a genetic sample.

Melissa Harris-Perry: Talk to us about the findings. What are the key takeaways from this study? What makes these polar bears different?

Kristin Laidre: We lay out evidence for a previously undocumented and very highly isolated sub-population of polar bears living in Southeast Greenland. Our results show that these are the most genetically isolated polar bears on the world. A lot of that has to do with geography. There's at the end of the line. They're at the southern extent of the range. They're locked in by the Greenland ice cap and open ocean and a big current. They have been living in this area for what we think is at least several hundred years.

Once we realize these bears were very local, meaning they really don't move very far, we asked ourselves, "Well, how could you have this population of bears in this area?" The reason we ask that is the sea ice in Southeast Greenland, the sea ice season is very short. It's on average around 100 sea ice covered days per year for a polar bear to hunt seals. That's just way too few.

The bears are using that sea ice when it's there, but it's just not long enough for a bear to hunt enough seals and get fat enough to survive a fasting period. What we could see from our data is that when the sea ice disappears, they actually move deep into the fjords and they are hunting on what we call the glacial mélange. Glacial mélange is essentially freshwater ice that comes off the Greenland ice sheet.

Melissa Harris-Perry: The freshwater makes them different in terms of how they're able to hunt relative to this broader conversation you were having about sea ice?

Kristin Laidre: They use the same techniques to hunt seals on the sea ice as they do on the freshwater ice. It's just that it's uncommon to have access to this freshwater ice. They're using the same hunting techniques, it's just that they're able to supplement an environment that has a very short sea ice season with this freshwater ice and that's how they survive down there.

Melissa Harris-Perry: Okay. These genetically distinct distant cousin polar bears have this other adaptation with this short season. I feel like I've been hoodwinked and duked a little bit by the headlines that were telling me that polar bears have figured out how to adapt to climate change by hunting on freshwater ice. Are you just telling me these are different bears with different hunting techniques, rather than an adaptation of the bears I thought had learned something new?

Kristin Laidre: Yes, and that's a little unfortunate. These bears are just like other polar bears in the Arctic. They just are lucky in that they live in an environment where they have a supplemental type of habitat to use. These bears are also vulnerable to climate warming. They're also dealing with-- Glaciers are retreating, the sea ice is going away, but these bears have basically found a way to hang on in an area that is unique. We don't see this habitat across most of the Arctic. Most polar bears don't even have this as an option.

Melissa Harris-Perry: If there's not that particular hope, is there some other kind of hope associated with what you've learned here?

Kristin Laidre: Yes, I think there's a couple of hopeful things. I think first is we've identified a population of polar bears we didn't know about and they are very genetically unique. We know that genetic diversity plays a role in conservation. I think the second piece that is hopeful is that with future monitoring, really future studies of these bears, we can learn a lot.

We can look at how they continue to persist in this environment over the next few decades and understand really, how and where polar bears might be able to hang on in an ice-free Arctic. When we talk about that as ecologist, it's the word persistence. Where might a species persist when much of their habitat is gone. It is quite possible that this glacial ice will support small numbers of isolated groups of polar bears, but it's not going to be big numbers of polar bears.

Melissa Harris-Perry: What about humans? Is there something that can be learned here about adaptation for our species?

Kristin Laidre: Global climate warming is going to affect humans in many different ways. We're headed towards 1.5 degrees warming pretty soon here. If you care about ecosystems, if you care about humans, if you care about polar bears, climate action is the number one most important thing that we can do.

Melissa Harris-Perry: Kristin Laidre is principal researcher for the Polar Science Center at the University of Washington. Thanks so much for your time today.

Kristin Laidre: Thank you very much.

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