Why mosquitoes arrived in Iceland for the first time

HostIceland has always been this lucky place where you can spend all summer outside without ever hearing that high buzzing sound in your ear. It was one of the only spots on the map where you didn't have to worry about getting a single bite. But that long run of good luck seems to be coming to an end. Why is this bug-free world finally starting to change?

GuestIt's a huge shift for a place that has been a safe spot for so long. For years, the only mosquito in the whole country was stuck inside a jar of alcohol at a museum in the capital city. A traveler found it on a plane back in the eighties and caught it. That was it. One bug. But lately, people are seeing them for real. The main reason they stayed away for so long wasn't just that it gets cold. It was how the cold behaved. Most cold places like Alaska or the north of Canada have a very steady rhythm. It gets cold, stays frozen for months, and then warms up. Iceland is much more moody. The weather there can go from a deep freeze to a warm thaw and back again in just a few days. That back and forth is what kept the bugs away.

HostThat sounds like it would be harder on the bugs than just a long, deep winter. Is it because they get confused by the warmth?

GuestYou can think of it like a trap. Mosquitoes spend the winter as tiny eggs or young ones in the water. In a place like Greenland, they stay frozen solid until the big spring melt. But in Iceland, the sun might come out in January and melt the ice. The baby bugs feel that warmth and think it's time to wake up. They start to grow and get ready to fly. Then, two days later, a blast of arctic air hits and the water freezes solid again. They're not ready for that second freeze. They have already used up the energy they saved for the winter. So they die before they can ever reach the age where they can fly and bite. The weather basically tricks them into waking up too early over and over until they're all gone.

HostSo if that weather trap worked for thousands of years, what broke it? It seems like it would still be a pretty wild place for a bug to live.

GuestThe trap is losing its teeth because the winters are getting much softer. We're seeing more days where the ground doesn't quite freeze all the way through, or the warm spells last long enough for the bugs to actually finish growing. The big change is in the soil and the ponds. If the water stays liquid or even just slushy for a little longer each year, the bugs can make it through. They're very tough. They just need a small window of time where the weather doesn't try to kill them every single week. On top of that, the whole country is getting a bit greener. There are more trees being planted and more places for the bugs to hide from the wind. It's becoming a much more friendly home for them than it used to be.

HostI always thought they just couldn't handle the cold at all, but they're clearly tough. If they weren't there before, how are they getting across the ocean now? They're too small to fly all that way from Europe or America.

GuestThey're world class hitchhikers. Most of them are probably arriving the same way that museum specimen did. They fly onto a plane in London or New York and hide in the cabin. Or they get stuck in a shipping container full of plants or tires. A tire is a perfect home for them because it can hold a little bit of old rainwater that never quite spills out. It only takes a few eggs in a puddle of water inside a truck or a ship to start a whole new group. In the past, those travelers would land, try to hatch, and get hit by that crazy Iceland weather. Now, they're landing and finding that the world outside the airport is actually quite nice.

HostIt feels like such a small thing, but a few bugs can really change how a place feels. Is there a chance they might actually be good for the local birds or the fish?

GuestThere's always a balance to these things. In other parts of the far north, mosquitoes are a huge part of the diet for birds that fly in for the summer. They provide a massive burst of energy for babies in the nest. But they also change how animals act. In places with big swarms, reindeer will stop eating and just run for hours to try to get away from the bites. They lose weight because they're too busy hiding to find food. In Iceland, the sheep and the local birds have never had to deal with that kind of stress. Their bodies and their habits aren't built for it. So even if they provide a little more food for some birds, the constant pestering can wear an animal down.

HostIt's strange to think that such a small creature can signal such a massive shift in how the planet is working.

GuestThe bugs are like a tiny thermometer that tells us the ground isn't as cold as it used to be. They're moving into new spaces because we have opened the door for them, and once they find a way to survive that first winter, they're likely there to stay.

HostThe museum jar might not be the only place to see a mosquito in Reykjavik much longer.

GuestThe old weather trap that kept the island quiet for so long is finally starting to spring a leak.

HostThe empty skies over those green hills were a rare gift while they lasted.