The Future of Forests

| 6/28/2011 10:12:39 AM

Dying TreesI keep hearing about how pine beetles are killing whole sections of forests. How serious is this problem? Are our forests dying? 

The mountain pine beetle epidemic that has been occurring throughout the West for the past few years understandably has many people concerned. From British Columbia to Montana to Colorado, pine beetles are killing millions of lodgepole, white bark and ponderosa pines. While this affects recreation, wildlife and aesthetics, it doesn’t mean the end of our forests. Bark beetles are a natural element of Western forest ecosystems; outbreaks such as these have occurred before, and the forest has recovered. Already, new seedlings and surviving trees are thriving in the open conditions created by the beetles. The question now is what the future forest will look like given additional pressures from climate change.

Historically, native bark beetles served as an “occasional” agent of forest disturbance, similar to fire, disease and wind. The beetles went through population booms and busts depending on temperature fluctuations, drought and the availability of vulnerable forest stands. Typically, when temperatures fall below minus 30 degrees Fahrenheit for several days running, it ends population outbreaks, but warmer winters caused by climate change are allowing more beetles to survive than ever before. Also, widespread forest disturbance caused by logging and fires at the end of the 19th century created conditions that favored lodgepole pine, resulting in the establishment of stands dominated by this single species that have now reached a vulnerable stage throughout the West.

Unfortunately, after a bark beetle outbreak has begun, options for curtailing infestations are limited, and harvesting beetle-killed forests may simply start the cycle over. Attempting to harvest large amounts of this dead wood may exacerbate the problem by increasing erosion and damaging surviving trees. Beetle-killed trees should only be logged where they represent a hazard to people, such as near homes, roads or other infrastructure.

As a sign of climate change, the current bark beetle outbreak raises alarming questions about the future of our forests. Scientists have long thought that climate change will manifest as more frequent droughts and extreme events, and our Western beetle epidemic is consistent with this prediction. Thus, while the impact of this outbreak is not unprecedented and recovery already appears to be underway, the future of Western forests is far from certain. Future management will need to be experimental in nature, trying new techniques in some places while protecting and monitoring conditions in others.

Mother Nature always takes corrective actions. In this case, the widespread uniformity of forest conditions resulting from 19th-century disturbances are being “corrected” into a more diverse condition with more species and likely more open, drought-resistant stands. This diversity should help increase resilience to future climate change compared with forests before the beetle outbreak, but the long-range prospects for these forests aren’t clear. Will these forests continue to develop, or will they succumb to other consequences of climate change? We do not yet know, but for now, the current bark beetle outbreak does not appear to be the end of America’s forests.

Martin Twer
12/12/2011 7:01:50 PM

One issue not addressed in the above article are forest fires. With large and continuous parts of the landscape now covered with dead trees, the severity and intensity of forest fires will potentially increase. While fire is one of the natural agents of disturbance in these ecosystems, it remains to be seen what the effects will be in the short and long term under these extreme conditions (compounded by climate change as well). If fires burn long and hot, there is chance that most organic matter (roots, humus, etc...) in the soil will burn as well, leaving a more or less sterile substrate without the components that "hold it together". This could dramatically increase erosion risk and diminish the chances for fast re-vegetation that would stabilize the soil. Some of us might remember images of large mud slides and slumps as a result of barren ground in combination with major precipitation events. These present "a hazard to people, such as [...] homes, roads or other infrastructure" as well and might justify dead tree removal/logging BEFORE the fires, not only in the immediate area surrounding those structures.

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