Drought harming N.M. forest health

State report finds risk of mass tree die-off

New Mexico’s relentless drought is stressing forests, making them more vulnerable to a widespread pest infestation that could cause a mass tree die-off if wetter weather doesn’t come, a newly released state report says.

The 2020 state report on New Mexico’s forest health looked at how extensively pests killed and damaged trees on national, state and tribal woodlands.

Drought conditions have worsened, encompassing half the state at the beginning of 2020 and then growing until

every area of New Mexico was deemed in some level of drought by the year’s end, the report said.

“Drought and warming temperatures have been linked to amplified tree death,” the report said. “Consequently, if these conditions remain similar in 2021 then tree death may increase in direct response to drought and warming or indirectly by being more attractive and susceptible to bark beetle attack.”

Dehydrated trees can’t maintain healthy canopies nor can they produce the sap needed to repel pests — a double whammy.

Aerial surveys found beetles last year had killed trees on 60,000 acres and damaged trees on several hundred thousand acres, the report said. It noted that not every tree on every acre was affected.

This could be a mild foreshadowing of what’s to come if the drought doesn’t let up, experts say.

“The beetles have probably emerged in the last month, so as they start attacking trees, we’ll be seeing a lot more in the coming months,” said John Formby, a state Forestry Division entomologist who helped write the report.

Researchers say last year’s drought, which caused by an exceptionally light snowpack and monsoon, could become more the norm as climate change creates warmer, drier weather throughout the Southwest.

The state has been in a mostly dry period since the late 1990s. This winter is one of the driest in recent memory, compounded by La Niña, an ocean cooling event that reduces evaporation and results in even more arid conditions in the Southwest.

The piñon pine, New Mexico’s official state tree, is especially vulnerable.

An estimated 350 million piñons died statewide in the early 2000s and millions more died a decade later when harsh drought conditions led to severe beetle infestations.

Formby said he is seeing reports of dying piñons.

“Nothing major,” he said, “but definitely some more piñon mortality creeping in.”

At the same time, large expanses of Ponderosa pines have yellowed, a clear sign of drought stress that is lowering the trees’ defenses, Formby said.

Researchers will know more after this year’s aerial surveys are conducted in the summer, he said.

The spruce beetle has been the most devastating recently, leaving dead trees scattered across more than 31,000 acres, the report said. Again, only some trees were killed on each acre.

The report also estimates invasive beetles:

◆ Killed ponderosa pines on about 12,000 acres.

◆ Killed mixed conifers on about 13,000 acres.

◆ Killed piñons on several thousand acres.

Formby said he was “pretty darned concerned” about the overall trends of piñon and ponderosa pines. Those trees grow mainly on state and private land, which make them his agency’s responsibility, he said.

A lot of bark beetles were found east of Santa Fe, and they expand from there, he said.

“Our prediction for this year is that we will likely see an uptick in the amount of bark beetles — probably most apparent in the piñon woodlands,” said Andrew Graves, head entomologist for the U.S. Forest Service in New Mexico.

The agency doesn’t try to combat pests with insecticides because it’s too expensive and impractical, Graves said.

It costs $200 to $500 per tree, and must be done as a preventive measure, Graves added, because once a beetle infests a tree, it’s too late.

“It’s just too many trees to spray … before the bark beetles come out,” Graves said.

Both Graves and Formby say the piñons that survive the last two die-offs might be hardier stock that can better withstand the harsh conditions brought on by climate change.

But Graves said he has doubts that a tree could evolve that quickly.

Graves cautioned people who collect firewood from national forests to make sure it’s not from freshly felled trees that might be infested with beetles. They could end up spreading the insects to the trees in their yards, he said.

Choose wood from trees that look older and drier, he advised, noting beetles will abandon a tree a couple of months after it dies.

Graves said although the forecast seems bleak, he still holds hope for a decent rainy season.

“A few good rains could really help,” Graves said.