Forests Lost To California Wildfires May Never Grow Back

Thomas Fire from 2017. BrittanyNY/Shutterstock

Jack Dunhill 04 Sep 2020, 15:24

A study looking at 1,840 square kilometers (710 square) miles of burnt area throughout the Southern Rocky Mountains has concluded that many of the trees lost in the flames this summer may never return. Wildfires continue to rage across much of California and Colorado, and although many are mostly contained as of now, scientists fear that irreversible damage may have already been done to affected forestry.

In a study published to Global Ecology and Biogeography, scientists from the University of Colorado Boulder found that changing conditions in the Southern Rocky Mountains will lead to just half of native tree species re-growing, with the projections being much worse if human greenhouse gas emissions stay constant.

"We project that post-fire recovery will be less likely in the future, with large percentages of the Southern Rocky Mountains becoming unsuitable for two important tree species – ponderosa pine and Douglas fir," said lead author Kyle Rodman in a statement.

A ponderosa pine seedling grows next to the burned remains of previous generations. Jason Cornell/Shutterstock

They surveyed 22 burnt areas, looking at the climate conditions and the abundance of seedlings in areas affected by wildfires. By comparing this to satellite images of pre-fire tree abundance, the team could get measurements on how successfully the forests were recovering from the loss of trees.

The results were that just half the ground was suitable for recovery, with those at higher elevations and more rainfall likely to bounce back than areas of less nurturing conditions. When compared to previous studies from the same areas, the team discovered the forests are recovering slower, if at all, than they did before. Even 15 years after a fire, as many as 80 percent of the plots the researchers surveyed had no new trees. 

As a result of climate change, the Southern Rocky Mountains are seeing conditions that are becoming both warmer and drier, increasing the frequency of wildfires while decreasing how likely the forest is to recover from it. Where trees should regrow, the researchers are predicting the areas to instead become grasslands.

"This study and others clearly show that the resilience of our forests to fire has declined significantly under warmer, drier conditions," said co-author Tom Veblen, professor of geography at CU Boulder. "The big takeaway here is that we can expect to have an increase in fire continue for the foreseeable future, and, at the same time, we are going to see much of our land convert from forest to non-forest,"

Alongside their observations, the team also input predictions of greenhouse gas emissions based on two scenarios: humans do nothing towards the climate crisis, and emissions stay the same; or a ‘moderate’ scenario, in which humans start reducing emissions after 2040.

If humans follow the "moderate" path, just 17.5 percent of the land will be suitable for Douglas fir and ponderosa pine by 2051. Predictably, if humans do not change emission rates at all, the number is significantly bleaker at just 6.3 percent and 3.5 percent for the fir and pine species, respectively.

The study serves as a stark reminder of the impact of climate change on native wilderness, and the importance of lowering emissions. In the short term, Rodman and the team hope that identifying the areas with the most likelihood of success when planted with seeds will allow initiatives to focus their resources on ensuring forest regrowth. They emphasize that we have not passed the point of no return, and progressing to a more sustainable future will help the forestry endeavor past current and future wildfires.

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