As expected, the 2015 wildfire season has meant more bad news for drought-stricken Western states. As of June 30, 45 wildfires large active wildfires burned from Alaska down to Arizona and as far west as Colorado. Wildfires in Southern California had driven thousands from their homes, while fires in Alaska have burned more than one million acres this year.

Separate from human interference, wildfires are a completely natural occurrence that help a forest ecosystem with regeneration and growth. But decades of fire suppression tactics combined with climate change have provided wildfires with an abundance of dry, dead fuel, leading to more fires and a longer fire season. Fighting wildfires also comes with a large price tag, with an average of $1.13 billion spent on wildfire suppression each year. With climate change, that price could increase to $62.5 billion annually by 2050.

But wildfires impact more than just forests and the economy — they can have far-reaching impacts on public health, water quality, and climate change.

“These cascading impacts are the things that keep me up at night,” Jason Funk, a senior climate scientist for the Climate and Energy Program at the Union of Concerned Scientists, told ThinkProgress. “We haven’t been looking at them so much.”

Fires Can Cause Choking Pollution That Rivals Beijing

Wildfires come with smoke — and as residential developments continue to blur the boundaries between forest and urban, communities are increasingly facing health risks associated with smoke pollution.

“In the West, we have a lot of development and people living in the wildland-urban interface, and they’re in a position to be exposed to smoke and wildfire risk when it happens,” Funk said. “It’s rather difficult to predict where these smoke plumes are going to end up.”

In 2013, Climate Central looked at air pollution related to 11 of the largest Western fires from the past 12 years, and found that in nine cases, the worst air pollution day of the year in a nearby urban area was caused by a wildfire. Fires that burned within 50 to 100 miles of a city often resulted in air quality five to 15 times worse than normal. And, on at least two different occasions, wildfires burning in Southern California caused air quality in cities like Los Angeles and San Diego to resemble that of Beijing.

The biggest threat from wildfire smoke comes from the fine particles present in the smoke, which can enter into the lungs through the eyes, mouth, and nose, or aggravate preexisting health conditions like lung or heart disease. In 2007, during a period of sustained wildfires near San Diego, six area hospitals saw a 25 percent increase in respiratory syndrome diagnosis, and a 50 percent increase in asthma diagnoses.

As climate change accelerates snowpack loss across the West and drives up temperatures, wildfire seasons are expected to increase in length, with wildfires becoming more numerous and potentially more intense. That means more days of the year where communities could be exposed to lowered air quality due to wildfire smoke.

Eroding Soil Can Pollute Already Depleted Water Sources

As fires burn through forests, surface vegetation — trees, bushes, even leaf coverings — also burn, exposing soil to erosion. Soil erosion makes it easier for sediment and pollutants to make their way into water sources, diminishing water quality for fish and humans alike.

“It’s easier for water to runoff of a burned area than a forest area, because forests act as sponges,” Sheila Murphy, a research hydrologist with the National Research Program at the U.S. Geological Survey, told ThinkProgress. “Immediately after a fire, there’s an impermeable layer [of soil], and there’s no vegetation or trees to slow [runoff] down.”

According to the University of Wyoming, the annual volume of runoff in the year after a fire can be as much as 30 percent more than the year before, and impacts of soil erosion from wildfires can be seen as far as 100 miles from the actual site of the burn. High-intensity fires tend to impact soil erosion more than low-intensity fires, because they destroy greater amounts of surface cover.

Streams or watersheds that are located within the area of a burn can experience higher levels of sediment runoff after a wildfire, especially when the fire is followed by a major precipitation event — even if that storm comes months after the fire has finished burning. As soil runoff increases in streams and watersheds, fish are often the first to be negatively impacted — ash from the fire, for instance, can cause a stream’s pH levels to increase, or clog a fish’s gills. According to the USGS, many native fish species have evolved within a particular fire regime, and are capable of surviving natural wildfire cycles. But with wildfires becoming more common — and with the season stretching on longer — species could have a difficult time adapting, something that Funk says could spell trouble for both fish and fisheries.

“Probably all through the Pacific Northwest we’re going to see an impact on fisheries,” he said.

As sediment from increased runoff moves farther downstream, it can eventually end up in reservoirs, forcing municipalities to spend more on water treatment in order to remove sediment and pollutants before the water can be used as drinking water. Sediment from fires often contains high levels of pollutants — like nitrates leeched from burned plant tissues — which in high concentrations can be harmful to human health. Following the 2010 Fourmile Canyon Fire in Colorado, high-intensity precipitation events that happened as much as 10 months after the wildfire caused significant changes in water quality that, according to the USGS, had “the potential to profoundly influence downstream water treatment processes, water-supply reservoirs, and aquatic ecosystems.”

“In the western U.S., part of the problem is we have limited water resources and we use up a lot of our water already, so there’s already stress on the water,” Murphy said. “Wildfire is an added stressor, in a way.”

Alaskan Fires Are Especially Bad News For Climate Change

In 2009, a multi-author study published in Science found that forest fires have a “substantial positive feedback on the climate system” — that the burning of forests releases carbon into the atmosphere, hastening climate change, which in turn impacts wildfire season.

But if longer, more numerous wildfires in the lower 48 are bad, scientists worry that an increase in Alaskan wildfires could be even worse. That’s because Alaska is home to vast tracts of permafrost — soil, rocks, and dead organic material that remain frozen all year. Permafrost stores a lot of carbon (some 1,400 gigatons, more than is currently in the Earth’s atmosphere), and a lot of Alaska sits on top of permafrost — about 85 percent of the state sits on top of some permafrost.

As of Sunday, more than 300 wildfires were actively burning in Alaska — a fast start to the wildfire season that could foreshadow a larger trend. According to a new report by Climate Central, the number of wildfires in Alaska has increased dramatically over the past decade.

“This is an area that has not seen regular fire for a very long time, maybe 5000 or more years according to some studies,” Todd Sanford, a climate scientist at Climate Central, told ThinkProgress in an email. “Scientists, in particular, are keeping an eye on the vast stores of carbon in these areas and how wildfire and warming in the region may put these at risk of being emitted and contributing to further warming.”

A lot of that carbon is stored in permafrost — and Sanford worries that increased wildfire activity could accelerate its melting.

“Wildfires can burn off the top vegetation layer that provides insulation for the colder layers of the permafrost. Also, wildfires can char and blacken the surface,” Sanford said. “These darker surfaces absorb more sunlight leading to increased surface warming, which can further accelerate thawing.”

As global warming continues to alter the Arctic climate — which has been warming twice as fast as the rest of the world, on average — wildfires in Alaska could become the new normal, a change that could have global ramifications.

“The risk of wildfires appears to be on the rise and future projections have a great deal more warming in store for Alaska in the coming decades meaning this is a risk that won’t be going away anytime soon,” Sanford said. “Fires in Alaska also have the potential to impact areas well beyond Alaska through degraded air quality and carbon emissions.”