Historic Fireffires Burn Rocky Mountain Forests Never Before • Protecting Children’s Health

A new study shows the U.S. West fire season in 2020 is pushing ecosystems to burning levels not seen in even at least 2000 years-a shocking example of how that is changing. of climate-changing ecosystems on which life and economy depend.

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By Philip Higuera, Bryan Shuman and Kyra Wolf

The unique drought in the US West there are people all over the region on the edge after fire record in 2020. Last year, Colorado alone saw the three largest fires in recorded state history, one that burned in October and crossed the Continental Divide wilderness above the tree line.

Those fires just don’t feel bad. The evidence now shows the 2020 fire season These ecosystems have been pushed to combustion levels unprecedented in at least 2,000 years.

That evidence, which we describe in a study published on June 14, 2021, serves as a compelling example of how climate change is changing life-dependent ecosystems and economies. A previous study almost a decade ago warned that by the middle of the 21st century, global warming could increase burning to past historic levels and transform some of Rocky Mountain’s forests. Our results show such changes in fire activity that are ongoing today.

Fire History Chart
Historically, fires have burned in the subalpine central Rockies every 230 years, on average. Much of that has increased in the 21st century. Photo credit: Philip Higuera

Enter uncharted territory

As paleoecologists – scientists who study how and how ecosystems have changed in the past – we have spent decades researching how fire, climate and forests change over time.

We can look back to when extraordinary events like multiple fires occurred and it is said thatwe have seen it before and our ecosystems are often back. ”In the last few years, however, it has become increasingly clear that many ecosystems are entering uncharted territory.

Having witnessed more and more wildfires burning in tall forests in 2020, which is not uncommon in the latter part of the season, we wondered if we had experienced a real unprecedented event.

In Colorado and Wyoming, the most fires in 2020 burned in a region where ours RESEARCH REVEALS tem has spent more than 15 years creating records of fire history and ecosystem change from materials stored beneath the lakes. This work focuses on understanding how climate change will one day affect fires. We looked at those records for an answer.

Evidence of past fires is preserved in lake sediments

When a fire burns in a forest, it sends small soot into the air. If there is a lake nearby, some of that charcoal settles to the bottom, adding to the layers that grow each year. By inserting a long tube of mud and extracting a core, we can examine the history of the surrounding landscape – revealed by the layers of everything that has sunk beneath thousands of years.

Carbon dating of tree needles and branches helps us determine the age of each layer of a core. Pollen stored in sediments can tell us what grew nearby. And the thick layers of charcoal told us when it burned.

We use such past fire records stored in the sediments of 20 lakes in the central Rocky Mountains. In all, the ten researchers who helped analyze these cores counted more than 100,000 small charcoal particles, within thousands of 0.5-centimeter layers of the lake’s surface. examined. Identifying the distinct increase in coal accumulation within the cores allows us to estimate when fire burned around a lake, and compares current patterns with those of the past.

The result: Many 21st century fires have not occurred in this region in the last 2,000 years.

Burned almost twice as often as before

We estimate that fires have burned forests around each lake once every 230 years, on average, for the past 2,000 years. Over the 21st century, the number of fires has nearly doubled, with fires now expected to burn in a given area once every 117 years.

Even more surprisingly, 21st century fires now burn 22% more frequently than the highest burning rate reached in the past 2000 years.

The first record was established about 1,100 years ago, during a period called the Medieval Climate Anomaly. The Northern Hemisphere at that time was 0.3 C (0.5 F) much warmer than the 20th century average. Submarine forests in the central Rockies during the early Medieval Climate Anomaly burned on average once every 150 years. To put the temperature outlook at that time, the Northern Hemisphere is in 2020 1.28 C (2.3 F) above the 20th century average.

In a previous study based on a subset of the same records, the Medieval Climate Anomaly stands as a mentor as can happen as the forests of Rocky Mountain warm. Research on boreal forests in central Alaska has also been documented unprecedented fires in recent decades.

Climate change is the cause, with associates

The current rise in fire activity across the West is clearly linked to research. more warm, dry summer and man-made climate change. Our evidence shows that the rate of burning over the past 2,000 years has also been in line with small climate variations. in the central Rockies.

hot, the drier the conditions the more easily the plants burn, the dice are loaded for the possibility of multiple fires. Human activities, a history of suppressing most fires and trees killed by insects all affect when, where and how the fire. These influences different throughout the West and each put on top of the warmer, drier conditions of the 21st century.

Adapting to a future unlike the past is a significant challenge land managers, policy makers and communities. Reducing the threats of increasing fires requires both combating climate change and learning to live in ways that help make our communities more numerous strong in our future fire.

Originally published on The Speech.

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