Depletion and Conservation of Natural Resources - U.s. Forests Under Stress
trees fire service national
The United States has 747 million acres of forested lands; they comprise roughly one-third of the nation's total land area. (See Figure 9.1.) Forests are valued for a variety of ecological and economical reasons. In their natural state they provide vital habitat for wildlife and play an important role in the carbon cycle. (See Figure 2.10 in Chapter 2.) Forests are also a source of recreation for humans and provide wood for fuel and lumber. Human uses combined with natural environmental stresses (such as disease and drought) pose a constant threat to the health and vitality of the nation's forests.
As shown in Figure 9.2 almost half of America's forested lands are in the hands of private owners with no ties to industry. Another 20 percent are part of the National Forest System overseen by the U.S. Forest Service, an agency of the U.S. Department of Agriculture. Other federal agencies control 13 percent of the country's forest lands. Industrial entities (such as timber companies) own 10 percent of America's forests, while the remaining 8 percent are under state control.
Forest Health—The Latest Government Assessment
In May 2003 the U.S. Forest Service published its latest assessment on the health and well-being of the nation's forests. According to America's Forests: 2003 Health Update, there are five key areas of concern:
- Outbreaks of native insects
- Nonnative invasive insects and pathogens (diseases)
- Invasive plant species
- Ecologically damaging changes in forest type
The Forest Service manages about 155 national forests across the country. (See Figure 9.3.) About 70 percent of these lands are located in the dry, interior areas of the western United States. Management practices in the past called for the Forest Service to put out all wildfires in the national forests. Scientists have recently put forward the idea that wildfires are necessary for forest health. They point out that wildfires are natural occurrences that serve to remove flammable undergrowth without greatly damaging larger trees.
Before pioneers settled the West, fires occurred about every five to 30 years. Those frequent fires kept the forest clear of undergrowth, fuels seldom accumulated, and the fires were generally of low intensity, consuming undergrowth but not igniting the tops of large trees. Disrupting this normal cycle of fire has produced an accumulation of vegetation capable of feeding an increasing number of large, uncontrollable, and catastrophic wildfires. Thus, the number of large wildfires has increased over the past decade, as have the costs of attempting to put them out.
Because the national forests are attractive for recreation and enjoyment, human population has grown rapidly in recent years along the boundaries scientists refer to as the "wildland/urban interface." According to a 1999 U.S. General Accounting Office (GAO) study, Western National Forests—A Cohesive Strategy Is Needed to Address Catastrophic Wildfire Threats, this combination of rising population and increased fire risk poses a catastrophic threat to human health and life along the wildland/urban interface areas. In addition to the risk fires pose to nearby inhabitants, smoke from such fires contains substantial amounts of particulate matter that contaminates the air for many hundreds of miles. In addition, forest soils become subject to erosion and mud slides after fires, further threatening the ecosystem and those who live near the forests.
In 1997 the Forest Service began an attempt to improve forest health by reducing, through "controlled burns," the amount of accumulated vegetation, a program to be completed by 2015. The GAO found that lack of funding and inadequate preparedness may render the program "too little, too late." The National Commission on Wildfire Disasters concluded: "Uncontrollable wildfire should be seen as a failure of land management and public policy, not as an unpredictable act of nature. The size, intensity, destructiveness and cost of … wildfires … is no accident. It is an outcome of our attitudes and priorities.… The fire situation will become worse rather than better unless there are changes in land management priority at all levels."
The summer of 2000 was considered the worst fire season in 50 years in the United States. Nearly 123,000 fires burned more than 8.4 million acres. Ironically, one of these fires resulted when a "controlled burn" near Los Alamos, New Mexico, raged out of control, sweeping across hundreds of acres of land and destroying homes and businesses for miles. In June 2002 a massive fire swept through Arizona destroying hundreds of homes and businesses and causing 30,000 people to flee. The fire burned 375,000 acres in only a week and was called a "tidal wave" by fire fighters trying to contain it. Numerous other fires roared through the American West during the summer of 2002.
According to America's Forests: 2003 Health Update, catastrophic fires are due to decades of fire suppression that have allowed forests to become overcrowded with highly combustible undergrowth. The situation is aggravated by a lingering drought in the West and trees stressed by pests and disease. The report warns that "the fire risk in many forested areas remains high."
Figure 9.4 shows the number of acres burned by wildland fires between 1960 and 2002. In 2002 federal agencies spent $1.66 billion putting out destructive wildfires.
Following the disastrous 2000 fire season the Forest Service collaborated with other agencies to develop The National Fire Plan, a long-term strategy for more effectively dealing with fire threats and preventing future wildfires. In August 2002 the Bush administration presented its plan for wildfire management in Healthy Forests: An Initiative for Wildfire Prevention and Stronger Communities. The so-called Healthy Forests Initiative implements core strategies of the National Fire Plan.
OUTBREAKS OF NATIVE INSECTS.
Native insects of concern in American forests include bark beetles and southern pine beetles. Under certain conditions these insects can infest huge areas of forests and kill thousands of trees. This is damaging by itself and exaggerates other threats to forests, such as wildfires. Wildfires are more likely to spread quickly and burn hotter when forests contain large amounts of trees that have been weakened or killed by insect damage.
The Forest Service estimates that southern pine beetles pose a moderate to high risk to more than 90 million forested acres across the Southeast. In 2001 beetle outbreaks affected tens of thousands of acres in the South resulting in $200 million of damages. The Forest Service spent $10 million that year alone fighting the beetle outbreak. In the western United States the bark beetle known as the Mountain Pine Beetle is a major killer of pine trees. Thousands of acres of pine forest across the West are considered at risk. The Forest Service focuses its resources on tracking, suppressing, and preventing beetle outbreaks and on replanting forests decimated by the pests.
NONNATIVE INVASIVE INSECTS AND PATHOGENS (DISEASES).
Another major threat to America's forests is the spread of nonnative invasive insects and pathogens. Non-native (or exotic) species can be very harmful, because they do not have natural predators in their new environment. This allows them to "invade" their new territory and spread very quickly.
Species of major concern to forest health are as follows:
- Gypsy Moths—An insect that arrived in the United States during the 1800s from Europe and Asia. In the springtime they devour newly emerged leaves on hundreds of tree species (primarily oaks). They are concentrated in eastern forests where they are blamed for defoliating more than 80 million acres of trees.
- Hemlock Woolly Adelgid—An insect that arrived in the United States during the 1920s from China and Japan. The pest eats the leaves off of eastern hemlock trees. It has infested hemlock forests across the Northeast and South Central states from Maine to northern Georgia. Trees die within only a few years of being infested.
- White Pine Blister Rust—A fungus native to Europe introduced to western Canada around 1910. It migrated quickly southward across the mountainous states where it is particularly lethal to high-altitude pine forests. Once firmly entrenched in an area the fungus can kill more than 95 percent of the trees it infects.
- Sudden Oak Death—A disease caused by the pathogen Phytophthora ramorum. Its origin is unknown, but it was introduced to the United States within the past few decades. So far, it has been found in forests in California and southern Oregon where it has killed thousands of trees (primarily oak) and ornamental and wild shrubs. Scientists fear that it could spread eastward and cause enormous damage to the country's massive oak forests.
- Emerald Ash Borer—An exotic wood-boring beetle from Asia that targets ash trees. Believed to have entered the United States in cargo packing materials, the beetle was discovered in Southeastern Michigan in the summer of 2002 and has so far killed millions of trees. Ashes are killed when the beetles' larvae bore tunnels within the wood, cutting off the tree's water and nutrients. Infested ash trees, which are predominantly in the Northeastern United States and Canada, die within two to three years of infestation.
The Forest Service employs a variety of measures to combat nonnative invasive pests, including application of insecticides and release of biological control agents. These agents include insects and pathogens found to prey upon the nonnative invasive pests. For example, since 1999 the Forest Service has raised and released more than 500,000 ladybird beetles into forests infested with Hemlock Woolly Adelgids. The beetles, which are native to the United States, feed on the Adelgids and their eggs. Experts hope this measure will wipe out nearly all of the Adelgid population in the forests treated.
INVASIVE PLANT SPECIES.
Insects and pathogens are not the only invaders causing damage to America's forests. Certain plants (native and nonnative) become a threat when they grow out of control and overpower regular forest vegetation. Invasive plants of major concern include leafy spurge in northern states (particularly in the West), kudzu in the South, and mile-a-minute weed in the Northeast and mid-Atlantic states.
Although these plants are most often a problem in rangelands they are increasingly affecting forests. Invasive plants strangle and smother young seedlings and gobble up resources, such as water and nutrients needed by other plants. They also contribute to buildup of highly combustible undergrowth, making forests more susceptible to hot-burning wildfires. This is one of the reasons that the National Fire Plan targets invasive plants for reduction. In addition, there is the Federal Interagency Committee for the Management of Noxious and Exotic Weeds. This is a collaboration of 17 agencies working to develop control techniques for invasive plants across the country. The Forest Service is working on a variety of measures, primarily biological agents (such as insects or fungi known to attack invasive plants).
ECOLOGICALLY DAMAGING CHANGES IN FOREST TYPE.
America's forests have been changed over the years by many human and natural factors. This has led to ecological changes in entire forest types. For example, prior to the 1900s the forests of the Appalachian Mountains were dominated by the American Chestnut. A fungus introduced from Europe virtually wiped out the chestnut population by the 1950s. Other species of trees soon became predominant. Today scientists consider this type of forest change to be harmful from an ecological standpoint. Major changes in forest type have profound effects on the overall health of a forest, wildlife habitat, and even soil conditions. The Forest Service worries that a combination of stressors, including fire, drought, destructive pests, and human activities, pose major dangers to forests. Human activities that can negatively affect forests include agriculture and residential development.
Forest Health—Other Problems
Environmentalists fear that the forests of the northwest United States are being depleted by "clear-cutting" practices—the method of logging in which all trees in an area are cut—as opposed to "selective management" techniques, in which only certain trees are removed from an area. The lumber industry continually battles with environmentalists and the U.S. Forest Service over the right to clear-cut ancient forests. Experts believe that North American "old growth" forests (stands of old, large trees) may store more carbon than any of the world's other sinks (repositories).
National Aeronautics and Space Administration (NASA) scientists report that satellite pictures show a high level of damage to the evergreen forests of the Pacific Northwest. They attribute the damage to clear-cutting and claim the region has been so fragmented by clear-cutting that the overall health of the forest is at risk. Many observers believe that the biggest threat from this logging technique is the loss of diversity of species in the area. The logging industry contends that restrictions on logging devastate rural communities by causing the loss of thousands of jobs and leading to an increase in retail prices for lumber nationwide.
Logging roads are increasingly blamed for contributing to landslides, floods, and changes in rivers and streams. The Roadless Area Conservation Rule was adopted in January 2001 to protect nearly 60 million acres of national forests from further road building and logging, while keeping them open for recreational uses. The rule had both environmental and economic goals. The Forest Service oversees approximately 386,000 miles of roads, and their upkeep costs billions of dollars. The high cost of building and maintaining these roads is often cited as a reason many national forests lose money on timber sales. The rule was immediately challenged in court by a variety of groups, but a federal appeals court upheld the rule in December 2002.
In an effort to counteract tree loss, forests are often "replanted" or replaced. Most experts contend that, when a natural forest (that has been replanted after clear-cutting) is replanted with commercially valuable trees, the plot becomes a tree farm, not a forest, and the biological interaction is damaged. Primary forests represent centuries, perhaps a millennium, of undisturbed growth. Trees will rebound after clear-cutting within 70 to 150 years but, researchers have found, the plants and herbs of the understory (growth under the canopy of the trees) never regain the richness of species diversity and complexity of their predecessors.
The Effects of Pollution
Many biologists believe that regional air pollution is a serious anthropogenic (made by humans) threat to temperate forest ecosystems. The most dangerous impact on forests comes from ozone, heavy metals, and acid deposition. Ozone exposure reduces forest yields by stunting the growth of seedlings and increasing stresses on trees. Such damage can take years to become evident. Numerous studies suggest that both photosynthesis and growth decline significantly after one or two weeks of ozone at levels of 50 to 70 parts per billion (ppb), more than twice the normal background level of 20 to 30 ppb. During growing seasons average ozone levels are highest in the West (California, Nevada, Utah, and Arizona) and on the East Coast south of Pennsylvania.
In 1995, in a four-year study of a widespread timber species called loblolly pine, researchers at the Oak Ridge National Laboratory in Tennessee determined that ground-level ozone levels that frequently occur in the eastern United States caused growth to slow, especially under drier soil conditions. The loblolly pine, covering approximately 60 million acres, contributes billions of dollars to the economy of the South.
In 2001 the Hubbard Brook Research Foundation reported that more than half of large-canopy red spruce trees in the Adirondack Mountains and the Green Mountains had died since the 1960s. Acid rain was considered the primary cause. Along with acid rain, the Environmental Protection Agency (EPA) also blames other pollutants and natural stress factors for the increased death and decline of northeastern red spruce at high altitudes (in the Adirondacks, for example) as well as the decreased growth of red spruce in the southern Appalachians. Acid rain is also closely linked to the decline of sugar maple trees in Pennsylvania.
In the March 1999 report Soil Calcium Depletion Linked to Acid Rain and Forest Growth in the Eastern United States, the U.S. Geological Survey (USGS) stated that calcium levels in forest soils had declined at locations in ten states in the eastern United States. Calcium is necessary to neutralize acid rain and is an essential nutrient for tree growth.