Global Warming and Western Forests

Western forests (including Alaska) cover more than 360 million acres across vast and often rugged terrain. Ranging from large fast-growing trees along the Pacific coast to high-altitude tree lines where tree size is smaller and growth much slower, most western forests are coniferous, although there are also significant hardwood forests.

The interspersion of western forests with shrub steppe habitats, mountain meadows and streams provide important habitat for a rich diversity of wildlife species ranging from songbirds to large ungulates such as elk, moose and deer.

Benefits for Humans and Wildlife

Western forests are extensively managed and harvested to supply wood for home construction and other purposes. In many areas of the West lumbering is the major economic driver. Forests and their interspersed grasslands provide grazing lands used extensively for ranching. These habitats also contribute greatly to water supply and quality, as well as air quality.

Western forests are very important for hunting, fishing and many other popular outdoor recreational activities, such as hiking.

Threats from Global Warming

Global warming will have a huge impact on western forests, and in fact already is. Warmer winter temperatures are contributing to unnaturally large, frequent and deadly outbreaks of bark beetles. As a result, nearly half of Colorado's 660,000 acres of lodge pole pine forests were infested by mountain pine beetles in 2006. Eastern Washington State lost 4million ponderosa and lodge pole pine trees in 2004 alone. Outbreaks have also occurred in Alaska, Arizona, California, Idaho, Montana, New Mexico, Oregon and Wyoming.

These tree-killing insect epidemics set the stage for catastrophic wildfires, especially in combination with the higher temperatures caused by global warming, leading to lower soil moisture. Moderate fire is natural and helpful in many ecosystems, but catastrophic, drought-fueled fire with abundant fuel from large acreages of dead trees can destroy vast expanses of wildlife habitat, put human lives at risk and cause extensive property damage. In the Western United States scientists have documented a six-fold increase in the area burned over the past two decades, which they attribute to global warming. These forest fires exacerbate the global warming problem because the burning forest releases more carbon dioxide into the atmosphere.

The economic costs of tree die-offs and catastrophic fires associated with global warming are almost beyond reckoning. Damage to homes and property from wildfires totaled $3.2 billion during the 1990s. In 2006 alone, the Federal government spent $1.5 billion to fight forest fires (throughout the U.S.). While loggers have in some places turned to harvested trees killed by insect epidemics, large forest fires lead to the loss of income and jobs in the logging industry. Continued warming and more severe droughts associated with global warming will only further increase the risks and costs of catastrophic wildfires.

Catastrophic fires are especially damaging when they destroy the fertile detritus layer of soils, leaving only highly erodible mineral soils. Reduced vegetative cover, increased erosion and higher stream temperatures are harmful to cold-water species such as trout.

Conservation Investments to Minimize Global Warming Impacts

Minimizing the impact of global warming on western forests will require extensive financial investment in a variety of management actions. The beetle outbreaks aided by global warming have created challenges for forest managers who must now incorporate new ecological, economic and social issues into forest management plans.

Forest managers need to research and implement new methods of suppressing large beetle outbreaks to avoid extensive loss of mature trees. They will also need to study methods of reducing fuel loads and fire risks without detriment to natural ecological cycles. This may require extensive increases in prescribed (controlled) burning, selective logging, and other techniques to reduce fire risk.

The cost of additional firefighting alone will be enormous. Already costing $1.5 billion annually, investing in additional fire management and control will be essential for minimizing an increase in fire risk associated with a hotter and dryer climate.

The increase in area burned requires extensive restoration efforts to minimize impacts. These efforts will need to include, among other things, reforestation and erosion control. Reforestation reduces water problems caused by loss of snowpack. It also will improve air quality, and enable sequestration of atmospheric carbon dioxide through growth.

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