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Benjamin Freeman’s fascination with birds began on a research trip to Bolivia, where he was stunned by the diversity of tropical avian species he found himself surrounded by. “Birds are really excellent subjects to study life on Earth,” he says. During graduate school, Freeman was researching disease in birds in the mountains of Papua New Guinea. But then Freeman, now a biologist at the University of British Columbia, unexpectedly fell ill himself. His experience taught him about how climate change is affecting the spread of diseases—which turns out to be more complicated than a simple march uphill. He told his story to science writer Ula Chrobak, recounted here.
One morning, I woke up on a concrete floor. I didn’t know how I had gotten there, to this hotel room in Lae, Papua New Guinea. My head was throbbing, and it felt like a really bad hangover. But I had been alone doing data entry the night before, so I was not hungover. It took a minute until I realized that I must have fainted.
I slowly realized what had happened. I had just been doing research on disease in birds up in the mountains and had arrived at the hotel the night before. I was not feeling that great and was grateful for a bed. I must have gotten out of bed that morning and immediately fainted. And I’m tall, I’m 6-foot-4. So it was really painful.
For me, getting malaria is, at least in part, a climate change story.
This is an environment with a lot of tropical diseases so it was like, “I need to find medical help.” The hotel owner was kind enough to take me to a clinic. I was thinking, “maybe I have typhoid, maybe I have yellow fever.” But it never crossed my mind that I could have malaria because I had been doing field work mostly at super-high elevations, and it was freezing. There are no mosquitoes there, and I’d been taking anti-malaria medication as a precaution.
At the clinic, the nurse took a blood sample, walked a few steps away to where the microscope was set up, and then a couple of minutes later, he said, “You have malaria, and you have falciparum”—the kind that kills a lot of people.
My very first reaction was: “That’s impossible. No way. This is unreal.” I got a shot in the butt, got some pills, went back to the hotel, slowly piecing it together: “Yeah, I did go down to a mid-elevation site where I slept for a night.” And I did remember getting bitten by mosquitoes there. But even the mid-elevation village was at about 5,000 feet. Everybody from there says, “Oh, no, we don’t have malaria here, it’s too cold.” But mine is not the only case of human malaria arriving in the New Guinea highlands.
As someone who was already studying tropical diseases in birds, I was curious: Do we see evidence that that’s what the birds are experiencing, too? The prediction would be that birds in the hot lowlands would have really high rates of avian malaria and that birds in the cool mountains would be uninfected.
Instead we found that it didn’t really matter what elevation the birds lived at. We took blood samples from more than 2,200 individual birds from 66 local species across 17 different sites, from sea level to the high mountains. Overall, about 40 percent of birds were infected, with only slightly higher infection rates near the coast than way up near 10,000 feet. And 10,000 feet is very chilly. I was totally surprised by that. I thought for sure it’ll be the same situation as human malaria, where there is more disease where it’s hot.
But for these birds, infection rates were more determined by what kind of bird they were. For these birds called berrypeckers, it didn’t matter if they were near the coast or way up high, they were almost uniformly infected. A group called whistlers, they were uniformly uninfected. The infected birds are largely able to do their bird thing, despite being infected. I suspect there’s been coevolution between the parasites and the birds’ immune systems over millions of years.
At least for these birds, we don’t see the pattern where warming is leading mountain birds to get infected more. Avian malaria can get transmitted by these little biting flies at 10,000 feet, not just the mosquitoes that need warmer temperatures. So we don’t predict that climate change will change things that much for the birds and malaria on the same mountain where it is changing things for human malaria.
This is not the case everywhere. For example, in Hawai’i, native birds have no evolutionary history with malaria, because that hadn’t existed there before Europeans introduced mosquitoes, so it’s just death to those birds. As it’s gotten warmer there, the mosquitoes have marched up, spreading diseases to resident birds as they go.
So I don’t have evidence this disease is changing for the birds in Papua New Guinea. But climate change does matter for them. It’s just more complex. Some tropical montane birds, including in Papua New Guinea and Peru, have responded to warming by living higher and higher on the mountain slopes. At the top of the mountain, there’s not much room, so it becomes, as the evolutionary biologist Mark Urban has put it, an escalator to extinction. The temperature changes, though, are not that big, and birds can handle being a little bit warmer. So it’s something in those changed ecological interactions—with what they eat, who eats them, how they get sick—that is dooming them. I’m working on new projects now to try to figure out what’s happening.
For me, getting malaria is, at least in part, a climate change story. I might not have gotten sick if this had been 20 years earlier, because the village I stayed in was right on the border of where malaria mosquitoes can survive and transmit the disease.
Catching malaria at 5,000 feet taught me that the impacts of climate change are here. Next I hope to learn more about what those impacts will mean for the future of these diverse birds. 
Ula Chrobak is a freelance science writer based in Nevada. You can read more of her work at ulachrobak.com.
Lead image: feathercollector / Shutterstock
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