Using a status-quo scenario for greenhouse-gas emissions, the Rocky Mountain Research Station office in Moscow, Idaho, projected the tree’s habitat will shrink steadily this century until practically blinking out with two small islands of ponderosa remaining above either end of the Rim by 2090.
The work is based on established growth zones similar to those that gardeners follow when choosing what to plant. Rising temperatures are shifting where the trees can survive, and Arizona’s forest already is on the southern edge of the species’ range.
The maps aren’t absolutes. Some trees may persist in unlikely places due to extraordinary genes, and other surprises may occur. But they portend a seriously altered ecosystem.
“It’s well-known in plant geography that plant distributions are controlled by climate,” said Jerry Rehfeldt, who retired from the Forest Service after helping map the futures of Western tree species. “So if climate changes, so does plant distribution. It’s quite simple.”
He expects chaparral and desert to encroach on Arizona’s pine country.
“The impacts are unbelievably huge,” he said, “especially in the interior West.”
The Arizona Legislature has been silent on climate change in recent years. The exception is repeated attempts by the Legislature’s far-right wing, unsuccessful so far, to block any policies that might stem from the 1992 United Nations conference on Environment and Development. Critics fear the “Agenda 21” that resulted from that treaty is an attempt to impose a one-world-rule on environmental matters.
State Sen. Chester Crandell, R-Heber, doesn’t believe climate change is man-made. His belief reflects that of many GOP members of the Legislature, which explains the absence of climate-related legislation.
“I’m not one that thinks in the scheme of things that we have a whole lot of effect on what the environment’s doing,” said Crandell, whose eastern Arizona district includes many areas hit by recent megafires. “We can pollute, we can do those kinds of things, but I’m not sure that in climate change ... that humans have that much effect on completely changing the climate in the world.”
Sandy Bahr, chapter director of the Sierra Club in Arizona, said the Legislature is out of step with the general public on climate change.
“Most Arizonans do believe in it,” Bahr said. “The problem is with our elected officials.”