Scientists say the parks and woods throughout the Great Lakes are experiencing shorter winters and displaced wildlife.

Chicagoans are already seeing bigger storms and less predictable seasons.

But some scientists predict people will soon see more concrete examples of changing climate: disease.

Scientists are predicting a greater danger of diseases like West Nile and Lyme disease as temperatures rise. Some even believe dengue fever could become a problem in the U.S.

“One of the things that we’re already seeing is a shifting of growing zones,” said Josh Mogerman, a spokesman for the Natural Resources Defense Council. “We’re seeing plants and animals that we would expect further south making their way into our region, and they’ll have a real impact on our natural environment here.”

Mogerman thinks for a lot of people, it will be a reality check.

“You know, when I think of dengue fever, I don’t think of the United States, I think of developing countries, like Heart of Darkness, and that sort of thing,” Mogerman said. “And I think this is one of those issues that really makes people sort of step back and say ‘whoa, this really is a problem.‘”

Diseases like Lyme, dengue, and West Nile are known as “vector-bound diseases.”

The vectors that carry these illnesses — ticks and mosquitoes — didn’t used to be a big problem in Chicago.

But a warmer climate is changing that.

Dr. Justin Harbison teaches at Loyola University’s School of Public Health.

“We know that mosquitoes develop more quickly when it’s warmer,” Harbison said. “And pathogens also go through their life cycle faster, and reproduce more quickly. So as the weather gets warmer, typically you’re going to get a more rapid disease cycle.” 

He says the worst case for disease is a short, warm winter followed by a dry summer. That’s what we saw in 2012, when the Illinois Department of Public Health reported almost 300 cases of West Nile virus.

Warmer weather also drives migrating deer north. They come with hitchhikers: black-legged ticks that carry Lyme disease.

The Illinois Department of Public Health has been reporting increasing cases of Lyme disease.

In 2002, there were only 32 cases. By 2012, there were over 200. The deer ticks that carry Lyme disease are now found in at least 35 counties in Illinois. In 2013 alone, they appeared in seven more counties.

The suburbs are of particular concern for Lyme disease. There, humans are more likely to come into contact with the animals that carry ticks, like woodland mice and deer.

Mosquitoes are the bigger problem in urban areas.

On a walk through Busse Woods in Chicago’s Northwest suburbs, Harbison pulled open an iron sewer grate to explain.

“This is going to hold water all year round,” Harbison said. “It’s polluted. West Nile virus is transmitted by a specific species that does very well in these polluted habitats, essentially.”

This isn’t limited to the Midwest, of course. And it’s about more than just ticks and mosquitoes.

“Health is where climate change starts to get very personal for people,” said Dr. Kim Knowlton, a top scientist for the NRDC. She says Americans are about to see all sorts of public health effects from climate change.

“The hotter it is, the more ground level ozone, which is basically smog,” Knowlton said. “And that is terrible news for people who have asthma. It’s making longer pollen seasons. There’s more and more of these climate-change-related exposures, and we, as a nation are becoming more vulnerable.”

That’s not to say there’s nothing we can do about it.

Public health officials in Illinois recommend getting rid of standing water to cut down on mosquito growth, wearing bug spray to prevent transmission, and knowing the dangers of these new illnesses.

Sean Kennedy is a reporter in Chicago. Follow him @stkennedy