Monday, March 14, 2016

Conifer die-off increases threat of wildfire

by Laura Paskus, New Mexico In Depth 

In the past few years, New Mexico has experienced huge, record-breaking fires in both the Jemez Mountains and the Gila National Forest. Big fires haven’t hit the Sandia district of the Cibola National Forest to the east of Albuquerque. But thousands of acres of dead conifer trees pose a hazard. That’s because after the trees die and dry out, they provide fuel for wildfires.

Silviculturists like the Sandia District’s Shawn Martin practice a specialty within forestry, managing forest health by paying attention to everything from tree sizes to insect types.

Insect outbreaks are a massive problem in southwestern forests, where drought and overgrowth have weakened millions of acres of trees. Two years ago, the Forest Service conducted aerial surveys over 21 million acres, and while the number of acres affected by new insect-related dieoffs was down from the previous year, it’s still high: Ponderosa-type bark beetles defoliated 70,110 acres in New Mexico; mixed conifer-type bark beetles, 66,620 acres; spruce-fir type bark beetles, 21,550 acres; and western spruce budworms killed more than 300,000 acres.

Such a challenge requires vigilance, which is why on a cloudy morning last October, Martin headed up the west face of the Sandia Mountains. About 10 miles above the Village of Placitas, he stopped to check an insect trap hanging from a tree alongside the gravel road. Bugs fill the sticky interior of the cardboard triangle; it’s part of an early warning system for Douglas fir tussock moths.

Over the past five years, those moths and fir engraver beetles have hit the higher elevations, while the piñon ips beetle infested lower elevation trees.

All told, there are about 9,000 acres of dead conifers in the Sandias.

According to Andy Graves, the district’s entomologist, these native insects did what comes naturally in an overly dense forest that hasn’t seen fire in decades and is experiencing drought: They took advantage of stressed and weakened trees.

While the insect infestations have declined with wetter conditions, the dead trees and overgrown brush still pose problems.

That’s obvious when Martin tries to hike toward some of the largest stands of dead trees. New Mexico locus, oaks, and chokecherries, along with miscellaneous prickly and stickery plants block the way. Chickadees and Northern flickers call from the thickets.

Had the forest been thinned, he says, or natural fires burned here over the past century, the trees would have been more resilient when the drought crept in beginning in the late 1990s.

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