If you like to take a walk in the woods in the United States or you prefer to decorate a tree at Christmas, you should know that climate change is making both of those activities a lot more 1.
Looking at two 2 and economically important species -- the Douglas fir and the Ponderosa pine -- scientists found that fires and drought 3 by climate change make new growth difficult, especially in low-elevation forests, according to a study published Monday in the Proceedings of the National Academy of Sciences.
Some forests in four regions in California, Colorado, the Northern Rockies and the southwestern part of the United States have crossed "a(n) 4 climate tipping (转折) point for post-fire tree generation," the study says.
Climate conditions over the past 20 years have 5 changes that would have taken decades or even centuries to 6 across broad regions of the country. This is leading to the sudden 7 of trees and making these lands increasingly unsuitable for tree regeneration.
"Climate changes is 8 our forests now, not just in some distant future. Maybe in areas where there are really 9 seed sources, there could be some trees, but it is becoming really hard to get these trees back due to climate change,"said study co-author Kim Davis.
The problem probably won't get any better, as climate change is making intense wildfires much more 10 . Western foresters say there used to be a fire season. But devastating and 11 fires have become a reality all year long. In 2018, fire cost California more than $9.05 billion, according to the USA insurance commissioner, the deadliest and most destructive wildfires season in the 12 history.
A higher number of fires and low seed availability means a high probability that these trees in these regions won't come back, Davis said. This study 13 on the driest and hottest areas of the Western forests, but researchers will next try to focus on how much will be impacted.
14, there are some things people can do to ease some of this problem. Forest management plans that reduce high-severity burns can help. Increasingly, forest managers are considering allowing some fires to burn under more moderate conditions, Davis said, Forest 15.
