What’s the Buzz on Beetles? – Clearcutting Forests

The real reason that clear cutting is prescribed for beetle salvage logging is purely economic. If beetle-killed pine is not harvested, the timber company does not get access to cheap timber (stumpage is roughly one-third of the usual), and the Annual Allowable Cut for the forest area will be lowered.

Further, the clearcut prescription for the war on beetles allows logging companies access to pine stands without having to go through the usual 60-day public review and comment period, and without having to pay the usual stumpage fee (even for healthy pine). The natural function of the Lodgepole Pine ecosystem is practically forbidden by current forest practices and policy.

We keep seeing that expedited (immediate) clearcut salvage logging is being prescribed by timber companies in order to deal with 'beetle infestations' or 'outbreaks.' They claim that beetles are 'attacking the forests,' that the beetle is 'aggressive' and that it poses a 'threat to forest health.' In some cases the course of action is immediate 'forest sanitation.'

This so-called 'destructive pest' is the mountain pine beetle (dendroctonus ponderosae)–a tiny black beetle about half the size of a grain of rice.

Once one starts reading the literature, this beetle doesn't sound so nasty after all.

The mountain pine beetle naturally exists at low (endemic) populations in all lodgepole pine forests. A pair of beetles will lay eggs within the inner bark of a tree. These hatch into tiny larvae who feed on the inner bark of the mature pine tree. If many beetles 'attack' the tree at once then they will likely kill it.

The beetle is a naturally occurring part of the lodgepole pine forest ecology. Beetles have been killing mature pine since the glaciers retreated. Beetles have also provided food for many beetle-eating birds such as woodpeckers for millennia. In return, these birds keep beetles at moderate levels. Mountain pine beetles are intricately woven into these ecosystems.

When climatic conditions (mild winters, warm summers) and food supplies (large lodgepole pine trees) are favourable over a long period of time, the small endemic populations grow into large epidemic proportions.

In a mixed species stand, if a beetle epidemic kills most of the pine, the other tree species will benefit from the space and take over.

In pure lodgepole pine forests, a beetle epidemic will kill a large percentage of the mature trees thus leaving behind a thinned out pine forest.

The trees that are killed by beetle will eventually fall down, then decompose or become fuel for an intense stand replacement forest fire. Pine will eventually regenerate the holes in the stand over time.

Contrary to common belief, the beetle will not kill all of the forest if we do not act.

Even in pure pine stands, some pine trees will survive. In some areas, lodgepole pine stands that are 140 to 250 years old exist. The beetle seems to be climatically limited when the weather is too cold. Epidemics end naturally when:

1. the food supply is no longer continuous enough to support the population, or
2. when there is a cold snap (-25%C) in early fall or late spring, or
3. when there is a sustained cold winter (< -40%C).

The mountain pine beetle is an integral part of the pine forest ecosystem. It is not going to go away and it cannot be exterminated. So next time you see clearcutting as the proposed method of dealing with beetle, think twice.

Clearcutting is not the answer
Clearcutting pine stands will not control the beetle. The beetle will continue to evolve new epidemics in uncut stands if the conditions are right. The reason for this is that it is already there but at very low levels. Only modifying stand or tree conditions to varied age classes and species mixtures will prevent epidemics.

Clearcutting will only reduce beetle hazard temporarily. The expanses of even aged, single species forest which (hopefully) regenerate following such a program will again be prime beetle habitat in 80 to 100 years, which is the short term in responsible forest management. Also, monocultures contain the lowest level of the beetle's natural predators and other controls, and are most susceptible to all forest pests.

What we can do is try to prevent a beetle epidemic.

Clearcutting the forest is the most common method of "dealing" with the beetle. The tactic is, get the trees before the beetles do. Yet endemic populations of beetles exist in every pine stand. Present at low populations, beetles are waiting for favourable conditions (warm winters, mature stands with low light intensity and low airflow) to increase their populations.

Tom Bradley's literature review on the Mountain Pine Beetle (1993) suggests the following:

"The only hope for long term control of pine beetle populations lies in managing the forest in such a way that habitat conditions never become favourable enough for epidemic populations to build up, and/or epidemics occur in geographically isolated pockets that will not spread extensively because the food supply is not continuous.

"Studies in the USA have shown that lodgepole pine forests can be selectively logged to create unfavourable habitat conditions for beetles. Thinning resulted in greater insolation, light intensity, wind movement, and a reduction in humidity. This effectively altered the stand microclimate enough to suppress beetle populations.

"Wind firmness of pine can be developed over time and successive entries. Mistletoe problems can be managed with careful leave tree selection." – Bradley, 1993

When it comes right down to it though, the solution is the development of a long-term, wholistic, insect management plan. This plan must recognize that there will be timber losses that will not be recovered. Wildlife habitat, travel corridors, streams and water quality, all need to be considered right at the beginning of planning.

Objectives of the plan need to prioritize healthy ecosystems that include beetle, not the sterilization of the landscape. Unlike what some in the forest industry would have us believe, this is not radiation therapy for cancer, but rather an additional factor to be considered by forest ecologists.

* Originally published in the East Kootenay Society Newsletter, February and March 2000.

* Sources

• Tom Bradley, 1993. Mountain pine beetle literature review. Sylva Ecosystem Consultants Ltd.
• L. E. Maclauchlan, and J.E. Brooks, 1999. Strategies and tactics for managing the mountain pine beetle, Dendroctonus ponderosae. BC Forest Service, Kamloops Region Forest Health. Brochure. 1999.
• Bark beetles in BC. BC Government.
• Steeger, M. M. Machmer, and B. Gowans, 1998. Impact of insectivorous birds on bark beetles: A literature review. Pandion Ecological Research Ltd.

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[From WS October/November 2000]