How Yellowstone 'erased' the scars of the 1988 fires

• Massive blazes ravaged nearly 500,000 hectares of Yellowstone National Park from June to November 1988, according to our partner The Conversation.

• Yellowstone's forest ecosystems regenerated rapidly, without human intervention.

• This analysis was conducted by Monica G. Turner, professor of ecosystem and landscape ecology at the University of Wisconsin (Madison, USA).

In the United States, from June to November 1988, massive fires ravaged Yellowstone National Park in Wyoming, affecting approximately 500,000 hectares of the park and its surroundings.

The subject of heavy media coverage, the size and intensity of the fires surprised scientists, park managers and the public.

Several media had proclaimed the total destruction of the park, which was totally false.

I was there during the fires and came back just after to see the damage.

Burnt forests stretched for miles, blackened tree trunks gave the impression of a desolate landscape.

Observing the park from a helicopter, however, we were surprised to see a mosaic of burnt but also intact plots.

I have studied the regeneration of Yellowstone's forests since 1989, watching landscapes of charred trees transform into lush young forests.

Fires play an important ecological role in many ecosystems and Yellowstone Park is no exception.

The local fauna and flora of the site are well adapted to these historical cycles of destruction and regeneration.

Today, the burnt landscape is dominated by young lodgepole pines.

Such fires mostly occurred in national parks or wilderness areas, where post-fire management was minimal.

It taught us a lot about the natural reactions of ecosystems to such events.

Yellowstone's forests are remarkably resilient, so the 1988 fires were not an ecological disaster.

Today, however, climate change and the frequency of fires could push forests beyond their limits.

​Heat, drought and strong winds

Extreme weather conditions started the 1988 fires and are responsible for many fires today.

The summer of 1988, unusually dry compared to usual summers in Yellowstone, is singled out as the main cause.

Indeed, that year, the quantities of combustible materials present (logs, pine needles, flammable trees) were usual.

The fires could only have been caused by high temperatures, drought and strong winds.

Gusts of more than 100 km/h had prevented me from flying over the fires in early July, well before the peak of the fire.

Roads, rivers and even canyons could not stop the flames which continued to spread when the wind was blowing.

Powerful gusts carried burning branches, spreading the fire.

The fires also continued to burn at night.

​How forests recover

During its last 10,000 years, fires have occurred in Yellowstone at intervals of 100 to 300 years.

“Crown fires” burn the canopy, killing trees while causing a sprout of new vegetation.

Such fires are common in Yellowstone, other high elevation forests, and in the North.

The thin bark of lodgepole pines burns quickly, but pinecones are adapted to fires.

When they heat up, they secrete large quantities of seeds, allowing the forest to regenerate after fires.

In addition, the fires create soils rich in minerals and are followed by sunny weather, ideal conditions for growth.

In Yellowstone, grasses and wildflowers were able to sprout from surviving roots because the land had not been deeply burned and retained essential nutrients for their growth.

Native plants also sprouted again.

Aspens were also able to establish from seeds sown through burnt pine forests, several kilometers from the nearest mature aspens.

These trees are doing well at higher elevations than before the fires.

Yellowstone's forest ecosystems regenerated rapidly, without human intervention.

I think that visitors no longer see the trace of the 1988 fires and admire the landscape, the fauna and the flora.

Similar regeneration mechanisms have been observed at Rocky Mountain (Colorado), Glacier (Montana), and Grand Teton (Wyoming) national parks, which have also evolved with fires over millennia.

Historically, high intensity fires kill trees, but do not destroy the forest.

​Climate change and fires

The 1988 fires ushered in a new era of major wildfires;

they are burning more and more forests every year.

Due to global warming, hot and dry weather, responsible for major fires, is no longer so rare.

The snow is melting earlier and earlier, fuels are drying up faster and faster, the temperature is breaking records and the fire season is getting longer.

Recently, fires have occurred in several national parks, including Bandelier, the Rockies, Glacier and Yosemite.

A hotter, drier climate aggravates drought in already hot and dry places.

In the western United States, climate change has dried up fuels and nearly doubled the area burned between 1984 and 2015.

Although lightning is responsible for most fires in the Rockies, human-caused fires lengthen fire seasons in populated areas.

Even in the rainforests of the Southern Appalachians, drought allowed a human-caused fire to spread from Great Smoky Mountains National Park to Gatlinburg, Tennessee, covering an area of ​​72 km2.

​What the future holds

In a warming world, even forests well adapted to large fires are no longer safe.

By the end of the 21st century, a hot, dry climate like the summer of 1988 could become the rule in Yellowstone.

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The frequency of megafires will tend to increase.

Such fires have already started burning forests long before they have had time to regenerate.

In Yellowstone and Grand Teton, fires in 2016 burned young forests that had previously burned in 1988 and 2000. Our studies of these recent fires showed that the fires were more intense and there were fewer shrubs born after the fire.

Also, the survival of these young trees in a warmer climate is not guaranteed.

Our "FIRES" file

National parks are the last untouched landscapes in the United States, and our best laboratories for understanding environmental change.

Research on the 1988 fires has become a benchmark for assessing the effects of fires today.

Yellowstone will maintain its beauty, its native species and its ability to inspire us.

However, only time will tell if its forests will retain their resilience to fires in future decades.

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This review was written by Monica G. Turner, Professor of Ecosystem and Landscape Ecology at the University of Wisconsin (Madison, USA).

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