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#ISeeChange: Is climate change responsible for SoCal's mosquito problems?

Over the last several months, KPCC has been asking you to share observations about your environment for a project called #ISeeChange.  The goal?  To have you-our audience-help us look for possible signs of change, climate and otherwise, in your backyard. We collect your observations, look for patterns and then share them with scientists to get their take. In these dog days of summer, we’re following up on some of your favorite summer complaints: bugs and heat.

The observation

Learka Bosnak, a resident of Los Angeles, likes to spend time in her backyard during the summer. When she does, she says, she now finds herself using a blanket to cover her entire body — a novel effort to prevent bug bites — and one she didn't need to worry about not too long ago. 

“I’ve had welt-sized bug bites,” she said. “Normally other people are my insect repellent. I don’t get bitten. And this past year has been treacherous.”

Bosnak is not the only one who wrote in to us with observations that the number of bug bites they receive seem to be increasing.

The questions sound a lot alike: “Why have the mosquitoes gotten worse?”

Interactive: Explore #ISeeChange observations

Mosquitoes are hard to count, easy to find

Levy Sun, a spokesman for the Greater Los Angeles Basin Vector Control, says it’s hard to know if mosquito numbers are growing. County mosquito technicians set traps every year, but there’s no historical census or population estimate.

But according to Sun, California has seen increasing variety in its mosquito population. “The mosquitoes that we’ve had here, have always been here,” Sun said. “Now we have more, new ones in our cities.”

Invasive Aedes aegypti and Aedes albopictus mosquitos may have come here through global trade or travel. They could spread yellow fever, dengue fever, and chikungunya.

So vector control has tailed them into the L.A. area — to communities including Whittier, Pico Rivera and Commerce — where technicians say they’ll find the mosquitos at one out of every three houses. 

Asian and Australian mosquitoes only need a capful of water to breed in, so the drought isn’t slowing them down, according to Vector Control officials.

“We used to say a season is summer, but because of these mild winters, mosquito season is yearlong practically. We don’t rest.” said Sun.  So controlling the mosquitoes becomes harder because their peak season is growing.

Mild winters are associated with climate change in California.

Warming predicted for Los Angeles region

Like most urban centers, greater Los Angeles temperatures have risen in the last century — by about 5 degrees. During that time, cities' populations swelled and became more dense. Forests and fields were paved over and covered with concrete, which helped fuel the rise in temperatures.

“We really have two factors,” said Alex Hall, UCLA atmospheric scientist. “One is the urban heat island effect. The other is global warming. And both of those are contributing to this warming we’ve seen over the last century.”

Hall’s team is predicting that climate change will warm the L.A. region another 4 to 7 degrees by 2100, and some places will get hotter than others.

“We know that in the future, oceans will warm much more slowly than land areas,” Hall said. “These areas that are influenced by the marine environment experience less warming than areas that are not.”

So, not only are there more kinds of mosquitoes here, but warmer temperatures will enable them to thrive.

Climate may be changing behaviors

Learka Bosnak knows her outdoor blanket strategy only goes so far. “I just put screens on my whole house,” she said.

She’s not the only one adapting to warm weather and the bugs they bring.

Kenny Tashman runs a hardware store in West Hollywood.  His screen business has been booming as Southern Californians — who like to open windows to cool their homes — respond to breeze and bug problems.

“I can tell — by the amount of people crying to me about when their screens are going to be ready — when it gets hot,” he said.

Demand for Tashman's services depends on the time of year. “Earlier in the year, spring, you’ll get more calls from the valley. Cause it’s a little warmer earlier there,” he says. “To the end of summer, it’s more West L.A.-type of customers because the valley gets too hot and everybody’s turning on their air conditioner.”

Tashman's business is likely to keep booming as the number of days of extreme heat rises. UCLA scientists are predicting climate change will give the L.A. region 3 or 4 times as many of them as we have now.

But Tashman says he’s ready: energy efficient windows can keep out the heat and, of course, the dreaded mosquitos.

#ISeeChange is a national effort to track how climate change is affecting our daily lives. 

Notice any bugs in your backyard lately? Wondering why you're seeing coyotes where you don't expect? Seen changes in your favorite tide pool? Snap a picture and tag it @KPCC and #ISeeChange on Twitter or Instagram, let us know through our Public Insight Network, or post your questions on Then see what others have found and observed in their environment.