The bark beetle feedback loop

 

Trees, you might say, are nature's ultimate do-gooders. A compound in the bark of Pacific yew trees fights cancer. Dead trees become nurse logs, nurturing forests' next generation of fungi and vegetation. In the ocean, rotting leaves boost the growth of plankton, fortifying the foundation of the sea's food chain. Living leaves scrub the air of the little nasties we humans like to overload it with: throat-irritating particulates and nitrogen oxides; world warming carbon dioxide. They are so skilled at sucking up CO2 that forests generally act as carbon sinks -- absorbing more CO2 than they put out, thereby tempering the effect of the climate changing gases we emit. 

In Western North America, though, bark beetles -- which proliferated during a series of warm winters -- have been steadily nibbling away at forests' ability to deliver this service. A few years ago, scientists predicted that by 2020, the beetles' tree killing spree in Canadian forests would have grown so prolific that the forests would become net carbon emitters. (When trees die, they not only stop absorbing CO2, they release what they've sequestered.) In other words, instead of mitigating climate change, they'd begin contributing to it. 

"This is the kind of feedback we're all very worried about in the carbon cycle," Andy Jacobson, a National Oceanic and Atmospheric Administration carbon cycle expert told the Associated Press in 2008. "A warming planet leading to, in this case, an insect outbreak that increases carbon dioxide in the atmosphere which can increase warming."

Now, new research out of British Columbia has delved deeper into the climate impact of all those dead trees, finding that summertime temperatures in beetle-killed B.C. forests have risen by about 1 degree Celsius, or about 1.8 degrees Fahrenheit. That's because live trees help to cool their local environment: "Trees sweat to help cool themselves in the same way that humans do," Holly Maness, an author of the study, told the Montreal Gazette. That "sweat" evaporates -- a process technically termed evapotranspiration -- moderating summer heat. "When you kill a tree, it's going to stop sweating. That means that solar radiation that was previously spent evaporating water from those trees is now going into heating the surface." 

The cascading effects of this uptick in temperature on local weather patterns and on things like the timing of spring runoff are, as yet, uncertain, according to the Gazette. "We've shown that the surface temperature increases that we've seen are sufficient to drive changes in cloud cover and precipitation, but it needs to be directly measured," Maness said.

Lest you finish this blog feeling totally depressed about the trajectory of our planet, consider what the study reinforces: the simple values of trees that we often take for granted. It says that there's something to programs in cities like L.A. to increase their urban canopy in anticipation of a warmer future, which to the the cynics among us might at first blush seem like mere feel-good stunts. Recognizing all that we're losing to the beetles also allows us to see what we have to gain by protecting the forests we still have and increasing tree cover in the places most of us live. Perhaps that age old tenet of DIY environmentalism -- to save the planet, plant a tree -- wasn't so dewy eyed after all. 

Cally Carswell is HCN's assistant editor. 

Photo: Beetle kill in Montana, courtesy flickr user LostDogPhotos, licensed under Creative Commons. 

High Country News Classifieds
  • WATERSHED PROGRAMS COORDINATOR
    Are you looking for a positive and success oriented work environment, the opportunity to join a (small but) dynamic group of people supporting watershed activities...
  • BACKCOUNTRY FILM FESTIVAL MANAGER
    Boise-based Winter Wildlands Alliance is looking for an experienced and highly motivated individual to organize our annual Backcountry Film Festival and Tour and coordinate additional...
  • LAND CONSERVATION MANAGER
    SUMMARY Leads, administers and manages the land conservation, conservation easement stewardship, and property management activities of the City of Fort Collins Natural Areas Department within...
  • CLEAN ENERGY PROGRAM ATTORNEY, NEVADA
    Position Summary: Western Resource Advocates (WRA) is seeking a Staff Attorney who is passionate about Western communities and the protection of the natural environment to...
  • EXECUTIVE DIRECTOR
    Deschutes River Conservancy in Bend, Oregon
  • WATER POLICY ANALYST WITH WRA (BOULDER)
    Position Summary: Western Resource Advocates seeks a passionate Water Policy Analyst with knowledge of western water issues to join our Healthy Rivers Team to strengthen...
  • GILA NATIONAL FOREST
    9+ acre inholding. Passive solar strawbale off the grid and next to the Continental Divide Trail in ponderosa pine/doug fir forest at 7400.
  • HIRING BEARS EARS EDUCATION CENTER DIRECTOR
    Conservation nonprofit Friends of Cedar Mesa in Bluff, Utah is hiring an Education Center Director to oversee the operation of the Bears Ears Education Center....
  • PROGRAM MANAGER, SUSTAINING FLOWS
    Friends of the Verde River, Cottonwood, AZ. Apply at https://verderiver.org/employment-opportunities/
  • PROGRAM ASSOCIATE - VERDE RIVER EXCHANGE
    Verde River Exchange - Friends of the Verde River, Cottonwood, AZ. Apply at https://verderiver.org/employment-opportunities/
  • CODE COMPLIANCE OFFICER
    Teton County Planning & Building is hiring! Our ideal candidate is a team-player, a problem-solver, pays attention to detail, and can clearly communicate technical material...
  • ARCHITECTURE DRAFTSPERSON/PROJECT MANAGER
    Studio Architects is seeking a full time Architectural drafts-person/project manager with1-3 years of experience to join our firm. At Studio Architects our mission is to...
  • ASSISTANT MANAGER/TRAINEE, COLORADO RANCH
    needed for 16,000+ acre conservation property in south central Colorado. Qualified candidate would have experience working on a ranch or wilderness property, general forestry/fire management...
  • FARM HAND &/OR NANNY IN ESCALANTE
    Nanny for 18-mnth-old. Yearly salary, vacation, health insurance. Spanish/other foreign-language native spkr prefrrd.
  • EXECUTIVE DIRECTOR
    Washington Association of Land Trusts seeks an ED to build on WALTs significant success & to lead the association to new levels of achievement. See...
  • EXECUTIVE DIRECTOR
    If you are deeply committed to public service and would like to become part of our high performing, passionate and diverse team, NCAT is looking...
  • BEAUTIFUL CUSTOM STRAWBALE HOME IN WESTERN COLORADO!
    Secluded, energy efficient Southwestern home on 40 wooded acres. Broker - Rand Porter - United Country Real Colorado Properties. 970-261-1248, $425K
  • FORMER RETREAT CENTER/CONSERVATION PROPERTY FOR SALE
    57 acres in Skull Valley, AZ, 17 miles from Prescott, year-round creek, swimming holes, secluded canyon, hiking/meditation trails, oaks, pines, garden, greenhouse. House, office building,...
  • HISTORIC RANCH HOME W/ 20 ACRES
    Historic 1893 Ranch Headquarters. 4 Bdrm, 3.5 Ba, 4000 ft2. Remodeled 2002. Includes 2 studio apts, stables, arena, workshop, 5 RV hookups. Chirachua & Peloncillo...
  • VICE PRESIDENT OF RETAIL OPERATIONS
    The Vice President of Retail Operations will provide overall leadership and accountability for purchasing, product development, merchandising planning, visual merchandising, retail operational excellence, oversight and...