Many tree species are projected to decline or die out due to a huge “migration” of trees across the Western North America due to global warming, insect attack, diseases, and fire, a new study finds.

In regions where these species have been present for centuries, scientists say some of trees will decline or die out, while others move in and replace them.

“In an enormous display of survival of the fittest, the forests of the future are taking a new shape,” the authors of the study wrote. The research was led by Richard Waring, professor emeritus at Oregon State University.

Researchers suggest that many tree species that were once able to survive and thrive are losing their competitive footholds and newcomers will eventually push them out.

"Some of these changes are already happening, pretty fast and in some huge areas," Waring said. "In some cases the mechanism of change is fire or insect attack, in others it's simply drought.”

The scientists predict that, the once-common species, lodgepole pine, will eventually be replaced by other trees, possibly ponderosa pine or Douglas-fir, while other areas may shift completely out of the forest and into grass savannah or sagebrush desert. Researchers have concluded that in central California, more than half of the species that are now present will not persevere in the climate conditions of the future, as global warming persist.

"We can't predict exactly which tree (species) will die or which one will take its place, but we can see the long-term trends and probabilities," Waring said. "The forests of our future are going to look quite different."

Waring explained that tree species that are native to a local area or region survive because they can most effectively compete with other species given the specific conditions of temperature, precipitation, drought, cold tolerance, and many other factors that favor one species over another in a specific location.

Therefore, a change in climate will force these species to decline or die out.

As climatic conditions change species that have been established for centuries or millennia will lose their competitive edge and will be unable to have the strength to withstand the new climate changes.

The study was done over a period of 4 years, using remote sensing of large areas, comparing 15 coniferous tree species that are found widely across much of the West in Canada and the United States, exploring impacts on 34 different “eco-regions” ranging from the Columbia Plateau to the Sierra Nevada, Snake River Plain and Yukon Highlands.

The study projected which tree species would be at highest risk of disturbance in a future that is expected to be 5-9 degrees Fahrenheit warmer by 2080, with perhaps more precipitation in the winter and spring, and less during the summer.

The researchers outlined the findings, in a release, which can be found below.

  • Some of the greatest shifts in tree species are expected to occur in both the northern and southern extremes of this area, such as British Columbia, Alberta, and California.
  • Large declines are expected in lodgepole pine and Engelmann spruce, and more temperate species such as Douglas-fir and western hemlock may expand their ranges.
  • Many wilderness areas are among those at risk of the greatest changes, and will probably be the first to experience major shifts in tree species.
  • Some of the mild, wetter areas of western Oregon and Washington will face less overall species change than areas of the West with a harsher climate.
  • More than half of the evergreen species are experiencing a significant decrease in their competitiveness in six eco-regions.
  • Conditions have become more favorable for outbreaks of diseases and insects.
  • Warming will encourage growth at higher elevations and latitudes, and increased drought at the other extremes. Fire frequency will continue to increase across the West, and any tree species lacking drought resistance will face special challenges.

"Ecosystems are always changing at the landscape level, but normally the rate of change is too slow for humans to notice," said Steven Running, the University of Montana Regents Professor and a co-author of the study. "Now the rate of change is fast enough we can see it."

Although the rate of change is increasing the process will take time, so our future environment is in danger and changes should be made now, however, there is only so much that can be done.

"There's not a lot we can do to really control these changes," Waring said. "For instance, to keep old trees alive during drought or insect attacks that they are no longer able to deal with, you might have to thin the forest and remove up to half the trees. These are very powerful forces at work."

One of the best approaches to plan for an uncertain future, the researchers said, is to maintain "connective corridors" as much as possible so that trees can naturally migrate to new areas in a changing future and not be stopped by artificial boundaries.

But a climate activist would likely say, we should just stop polluting our Earth in order to save our future “green.”