Beetle-killed forests are surprisingly rich in biodiversity

Imagine that.

Read the full article from Jonathan Romeo at the Durango Herald here. Below are some interesting snips from the article.

The Forest Service has long maintained such timber sales benefit the health of the ecosystem as it transitions from an old-growth to new-growth forest, but research from the University of Montana, as well as several conservation groups, challenges that idea.

“These areas where beetles killed trees is a really important habitat, ecologically,” said Chad Hanson, director of the John Muir Project, a nonprofit group opposed to salvage logging.

“It sounds counterintuitive, but for wildlife species, those areas are a bonanza,” he said. “Science is telling us these habitats are every bit as important as the forest before the kill-off.”

An infestation begins when a female spruce beetle finds a weak tree and signals to more beetles to attack. The insects chew through the bark and then enter a layer of the tree where they lay eggs in a network of tunnels. The eggs hatch, the beetles grow up and fly away. Before leaving, the mature beetles spread a special fungus in the center of the tree that ultimately kills it.

But it’s what happens after that Hanson says is so important for the ecosystem.

After the beetle moves on, woodpeckers feed on the larvae left behind, which creates nest cavities in dead trees for other species – such as bluebirds, chickadees and even squirrels – who are unable to make the safe havens themselves.

Then come the wildflowers, which thrive on the exposed understory of the forest, typically covered in shade. Flies and other insects arrive to feed on the flowers, and in turn bring birds, bats and other small mammals, which attract larger predators.

“What you end up with is a very rich and biodiverse ecosystem,” Hanson said.

Clark University associate professor Dominik Kulakowski agreed. He said the result, a “snag forest,” is a favorable habitat for many invertebrates and vertebrates because of the creation of canopy gaps and enhanced growth of understory plants.

“Outbreaks create snags that may be used by various birds and mammals, including woodpeckers, owls, hawks, wrens, warblers, bats, squirrels, American marten and lynx,” Kulakowski said.

By removing the trees, you remove this process, both Hanson and Kulakowski said.

In her 2014 report for the University of Montana, entomologist Diana Six said the long-standing method of thinning and salvaging does little to reduce to risk of beetles spreading and forest fires.

Instead, underlying conditions – warmer temperatures and drought – are the main drivers of those threats by allowing longer seasons for beetles to thrive and weakening trees to fight infestation. What has resulted is the largest outbreak of beetle kill recorded in human history.

“During an outbreak, these treatments are doomed to failure,” Six told The Durango Herald. “If warm temperatures and drought are driving an outbreak, by cutting trees you can’t reduce the outbreak because it doesn’t change the conditions.”

Six said it’s human nature to want to do something to address the problem, so methods like logging gain traction. The forests look devastated, and our gut feeling is ‘My God this has been terrible,’” she said. “But if we step back and look at forest processes, sometimes just standing back and not doing anything might be the best approach.”


7 thoughts on “Beetle-killed forests are surprisingly rich in biodiversity”

  1. Chad Hanson lives off of scare tactics and litigation. What is not stated. In California alone, in 2014, 909,000 acres of forest lands were at elevated rates of mortality. In 2014 there were 3.3 million trees killed. By 2015, aerial surveys taken over the entire Forest Service California region showed an estimated 29 million dead trees. The California Regions net growth of timber is 3,730.8 mmbf and the annual mortality is 842.6 mmbf or 22 percent mortality each year. Given these numbers and acreage, the US is allowing a more rapid deforestation than what we are concerned about in our tropical rain forest. Mr. Hanson has no concern for those issues, just trying to stop any reasonable treatment of forests to allow us to have the products generated from their wise use. He is also not concerned about the growing intensity of wildfires due to millions of dead trees left on the landscape to cause catastrophic soil and watershed impacts. There is nothing wrong with habitat variation, but not to the exclusion of wise use and management as well as compromise.

    • Ironically Bill, your comment here seems to be full of scare tactics.

      Meanwhile, here’s what Dr. Hanson said in the article, which doesn’t seem very scary at all, unless you fear a bonanza.

      “These areas where beetles killed trees is a really important habitat, ecologically,” said Chad Hanson, director of the John Muir Project, a nonprofit group opposed to salvage logging.

      “It sounds counterintuitive, but for wildlife species, those areas are a bonanza,” he said. “Science is telling us these habitats are every bit as important as the forest before the kill-off.”…

      “What you end up with is a very rich and biodiverse ecosystem,” Hanson said.

  2. The Forest Service harvests about 3% of the annual timber mortality on western national forests. The 97% left may be a bonanza for bluebirds, chickadees, squirrels, wildflowers, woodpeckers, owls, hawks, wrens, warblers, bats, American marten and lynx, but they enjoy this bonanza (on those areas where the fire intensity doesn’t sterilize the soil) at enormous economic and social cost to the human component of the ecosystem. Could they perhaps survive and prosper with a bit less than 97% ?

    It is a fact that thinning decreases interception of rainfall (more water enters the soil) and reduces transpiration (less leaf area) thus increasing water availability and reducing stress. The purpose of thinning, along with bettering wildlife habitat, increasing growth of quality trees and reducing stand density to lessen fire hazard, is to prevent future mortality. Thinning is not a treatment designed to stop an ongoing outbreak.

  3. Food chains – it all begins with the soil’s nutrients, rainfall/water, air, and solar energy. Any time the forest is opened up, through either human or natural means, more sunlight reaches the forests floor and plant/animal diversity increases. There is nothing counter-intuitive about this.

    Some years ago I was part of a group leading a week-long teacher-in-the-woods workshop. They were to form 3-4 member teams and, as a team, pose some sort of question. During the ensuing week, they’d answer the question. I remember this one teacher who felt the new plantation would have the least diversity, the 40-year forest would have more, and the old-growth would have the most. He was beside himself when the data his group had collected showed the new plantation had the most diversity followed by the old-growth and, lastly, the 40-year old forest.

    I told him that was pretty much what I’d have guessed. The plantation had lots of sunshine (i.e., there was still no crown closure); the old-growth had some canopy openings beginning to develop; and the 40-year old forest had a very dense canopy.

    We later learned this teacher had been a tree-sitter and, during the week, he’d made it quite apparent that he had little use for foresters. Now, how much of his biases entered his teaching is anybody’s guess.

    I’d also suggest that dense, over-stocked forests, if they aren’t already, will become less healthy and more prone to insect attacks, disease, drought, and, eventually, fire. By definition, dense, over-stocked forests have already exceeded their carrying capacity (i.e., there are not enough nutrients, water, and solar energy to maintain all the flora/fauna) and the forest’s health will decline. As noted, warmer temperatures and drought may be contributing factors but these are merely part of the land’s carrying capacity. The real question is: we can choose to let nature take its course (insects, disease, fire) or we can do something about it.

  4. It is no surprise to managers that these affected stands are biologically rich. The process of succession means that there will be a progression of different biological assemblages on these areas over time. Along the way, various components of the ecosystem will become prominent, and later fade away. Sure, woodpeckers are benefitting from the current situation, but what will their population be like in 50 years?

    This is a “straw man” argument. No manager will say that management activities are designed to “stop the beetle”. The areas being proposed for treatment are a trivial proportion of the total area affected by the beetle. All of the proposed treatments have secondary objectives including public safety, recreation and restoration.

    It is difficult to understand how observers can claim that conversion of over 90% of the mature spruce to a single, earlier successional stage will result in “very rich and biodiverse ecosystems”. On the contrary, diversification of ecological conditions across the landscape can be accomplished by initiating restoration efforts now. By using proven methods of salvage logging, site preparation and tree planting, managers can establish a wider range of age classes and species mixes to help create a more diverse and resilient forest for the future.

  5. Such a fascinating conversation.

    Just tossing in my $.02: I can’t comment on how much or how little beetle-killed wood is harvested, or what the effects are on people who benefit from those forests, or how these outbreaks and their effects ought to be managed.

    As far as public perception, though, I think there’s a sense that the beetles represent apocalypse: the trees will die, game over, end of forest. There isn’t an appreciation of future succession and the richness of those habitats. Articles like this and perspectives like Hanson’s would seem an useful corrective on that side of things.

    • In a humanless forest, we could allow old growth to take 500 years to return. We cannot do that today, because humans interrupt the “natural” succession. They have been doing that in the Sierra Nevada since last glaciers retreated back into their cirques.


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