Forests
Forests are dominated by trees and other woody vegetation. Roughly three-quarters of the forests used for commercial timber operations in the United States are privately owned. Many national forests were originally established to ensure a steady and reliable source of timber, and commercial logging companies are currently allowed to harvest U.S. national harvests, usually in exchange for a royalty that is a percentage of their revenues.
Humans have utilized forests for thousands of years as a source of energy, building materials and pulpwood for paper, and these uses remain important. When forestlands hold valuable mineral resources beneath them, they may be cleared to provide access to the minerals. Wood is used to build houses, burn for cooking and heat, and many other purposes. In the United States, timber makes up about 50% of the building materials for new houses. As the number of new houses continues to rise and houses continue to increase in average size, the amount of timber needed will continue to grow. Throughout the world, 2 billion to 3 billion people rely on wood as the primary heating fuel, and more than 20 million homes use wood for energy at least some of the time. In theory, cutting trees for timber if forest growth keeps up with foreset removal. Unfortunately, in South America, are cut intensively, allowing little chance for regrowth.
The United States Forest Service defines forestlands as lands that consist of at least 10 percent trees of any size. They include: transition zones (such as areas between heavily forested and nonforested lands) and forest areas adjacent to urban areas. Forests cover about one-third of the United States, which is about 70 percent of their extent when European settlement began in the 17th century. About 42 percent of U.S. forestlands are publicly owned. Of these, about 15 percent are in national parks or wilderness areas and are thus protected from timber harvest.
Other public forestlands are managed for various uses: recreation, grazing, watershed protection, timber production, wildlife habitat, and mining. Forests in the western states are predominantly publicly owned, while those in eastern states are predominantly privately owned.
Forests can be classified by their relative maturity. Old-growth forests have been undisturbed for hundreds of years. They contain numerous dead trees and fallen logs which provide species habitats and are eventually recycled through decay. Second-growth forests are less mature and occur when the original ecological community in a region is destroyed, either by human land-clearing activities or by natural disasters (i.e., fires, storms, volcanic eruptions). Humans sometimes create artificial forests in the form of tree farms. Usually only one tree species is planted in a tree farm. After maturing enough to be of economic value, the trees are harvested and new trees planted in their place.
Timber Harvest Practices
The two most common ways in which trees are harvested for timber production are clear-cutting and selective cutting. Clear-cutting involves removing all, or almost all, the trees within an area; it is the easiest harvesting method and, in most cases, the most economical. When a stand, or cluster, of trees has been clear-cut, foresters sometimes replant or reseed the area. Often the entire area will be replanted at the same time, so all the resulting trees will be the same age. Because they are exposed to full sunlight, clear-cut tracts of land are ideal for fast-growing tree species that achieve their maximum growth rates with large amounts of direct sunlight. Because other species may not be so successful in these conditions, there can be an overall reduction in biodiversity.
Clear-cutting can be economically advantageous but leads to soil erosion, increased soil and stream temperatures, and flooding.
Clear-cutting, especially on slopes, increases wind and water erosion, which causes the loss of soil and nutrients. Erosion also adds silt and sediment to nearby streams, which harms aquatic populations. In addition, the slopes are prone to dangerous mudslides. Clear-cutting also increases the amount of sunlight that reaches rivers and streams, which raises water temperatures that can adversely affect certain aquatic species. Many environmental scientists identify clear-cutting as a cause of habitat alteration and destruction as well as forest fragmentation which decreases biodiversity. However, in heavily forested regions of the country, such as the northern New England states of Maine, New Hampshire and Vermont, where forests can cover up to 85% of land area, a case can be made that clear-cuts actually increase habitat diversity and, as a result, species diversity.
Forests are dominated by trees and other woody vegetation. Roughly three-quarters of the forests used for commercial timber operations in the United States are privately owned. Many national forests were originally established to ensure a steady and reliable source of timber, and commercial logging companies are currently allowed to harvest U.S. national harvests, usually in exchange for a royalty that is a percentage of their revenues.
Humans have utilized forests for thousands of years as a source of energy, building materials and pulpwood for paper, and these uses remain important. When forestlands hold valuable mineral resources beneath them, they may be cleared to provide access to the minerals. Wood is used to build houses, burn for cooking and heat, and many other purposes. In the United States, timber makes up about 50% of the building materials for new houses. As the number of new houses continues to rise and houses continue to increase in average size, the amount of timber needed will continue to grow. Throughout the world, 2 billion to 3 billion people rely on wood as the primary heating fuel, and more than 20 million homes use wood for energy at least some of the time. In theory, cutting trees for timber if forest growth keeps up with foreset removal. Unfortunately, in South America, are cut intensively, allowing little chance for regrowth.
The United States Forest Service defines forestlands as lands that consist of at least 10 percent trees of any size. They include: transition zones (such as areas between heavily forested and nonforested lands) and forest areas adjacent to urban areas. Forests cover about one-third of the United States, which is about 70 percent of their extent when European settlement began in the 17th century. About 42 percent of U.S. forestlands are publicly owned. Of these, about 15 percent are in national parks or wilderness areas and are thus protected from timber harvest.
Other public forestlands are managed for various uses: recreation, grazing, watershed protection, timber production, wildlife habitat, and mining. Forests in the western states are predominantly publicly owned, while those in eastern states are predominantly privately owned.
Forests can be classified by their relative maturity. Old-growth forests have been undisturbed for hundreds of years. They contain numerous dead trees and fallen logs which provide species habitats and are eventually recycled through decay. Second-growth forests are less mature and occur when the original ecological community in a region is destroyed, either by human land-clearing activities or by natural disasters (i.e., fires, storms, volcanic eruptions). Humans sometimes create artificial forests in the form of tree farms. Usually only one tree species is planted in a tree farm. After maturing enough to be of economic value, the trees are harvested and new trees planted in their place.
Timber Harvest Practices
The two most common ways in which trees are harvested for timber production are clear-cutting and selective cutting. Clear-cutting involves removing all, or almost all, the trees within an area; it is the easiest harvesting method and, in most cases, the most economical. When a stand, or cluster, of trees has been clear-cut, foresters sometimes replant or reseed the area. Often the entire area will be replanted at the same time, so all the resulting trees will be the same age. Because they are exposed to full sunlight, clear-cut tracts of land are ideal for fast-growing tree species that achieve their maximum growth rates with large amounts of direct sunlight. Because other species may not be so successful in these conditions, there can be an overall reduction in biodiversity.
Clear-cutting can be economically advantageous but leads to soil erosion, increased soil and stream temperatures, and flooding.
Clear-cutting, especially on slopes, increases wind and water erosion, which causes the loss of soil and nutrients. Erosion also adds silt and sediment to nearby streams, which harms aquatic populations. In addition, the slopes are prone to dangerous mudslides. Clear-cutting also increases the amount of sunlight that reaches rivers and streams, which raises water temperatures that can adversely affect certain aquatic species. Many environmental scientists identify clear-cutting as a cause of habitat alteration and destruction as well as forest fragmentation which decreases biodiversity. However, in heavily forested regions of the country, such as the northern New England states of Maine, New Hampshire and Vermont, where forests can cover up to 85% of land area, a case can be made that clear-cuts actually increase habitat diversity and, as a result, species diversity.
Selective cutting removes single trees or a relatively small number of trees from the larger forest. This method creates many small openings in a stand where trees can reseed or young trees can be planted, so the regenerated stand contains trees of different ages. Because seedlings and young trees must grow next to larger, older trees, selective cutting produces optimum growth only among shade-tolerant tree species.
This approach allows most of the trees to remain, which helps maintain habitats and prevent soil erosion and allows uninterrupted recreational use. However, in tropical forests when only the biggest and best trees are removed, selective cutting can lead to significant ecosystem damage. Because the canopy of a tropical forest is thick and intertwined, the removal of one large tree damages a considerable area around it.
The environmental impact of selective cutting is less extensive than that of clear-cutting. However, many of the negative environmental impacts associated with logging remain the same. For example, whether a company uses clear-cutting of selective cutting, it will need to construct logging roads to carry equipment and workers into the area that will be harvested. These roads fragment the forest habitat, which affects species diversity, and compact the soil, which causes nutrient loss and reduction in water infiltration.
This approach allows most of the trees to remain, which helps maintain habitats and prevent soil erosion and allows uninterrupted recreational use. However, in tropical forests when only the biggest and best trees are removed, selective cutting can lead to significant ecosystem damage. Because the canopy of a tropical forest is thick and intertwined, the removal of one large tree damages a considerable area around it.
The environmental impact of selective cutting is less extensive than that of clear-cutting. However, many of the negative environmental impacts associated with logging remain the same. For example, whether a company uses clear-cutting of selective cutting, it will need to construct logging roads to carry equipment and workers into the area that will be harvested. These roads fragment the forest habitat, which affects species diversity, and compact the soil, which causes nutrient loss and reduction in water infiltration.
Logging, Deforestation, and Reforestation
Almost 30% of all commercial timber in the world is produced in the United States and Canada. Compared with South America and Africa, deforestation and land loss and destruction in these two major timber-producing countries have been relatively small over the last several decades. Still, timber production presents important ecological challenges in the United States and Canada.
All activities associated with logging disrupt the habitat and usually have an effect, either negative or positive, on plant and animal species. Logging often replaces complex forest ecosystems with tree plantations, which are large areas typically planted with a single rapidly growing tree species. These same-ages stands can be easily clear-cut for commercial purposes, such as pulp and wood, and then replanted. Because of this cycle of planting and harvesting, tree plantations never develop into mature, ecologically diverse forests. If too many planting and harvesting cycles occur, the soil may become depleted of important nutrients such as calcium.
Almost 30% of all commercial timber in the world is produced in the United States and Canada. Compared with South America and Africa, deforestation and land loss and destruction in these two major timber-producing countries have been relatively small over the last several decades. Still, timber production presents important ecological challenges in the United States and Canada.
All activities associated with logging disrupt the habitat and usually have an effect, either negative or positive, on plant and animal species. Logging often replaces complex forest ecosystems with tree plantations, which are large areas typically planted with a single rapidly growing tree species. These same-ages stands can be easily clear-cut for commercial purposes, such as pulp and wood, and then replanted. Because of this cycle of planting and harvesting, tree plantations never develop into mature, ecologically diverse forests. If too many planting and harvesting cycles occur, the soil may become depleted of important nutrients such as calcium.
Impact of Deforestation on the Carbon Cycle
Forests contain trees that absorb pollutants and store carbon dioxide. The cutting and burning of trees releases carbon dioxide and contributes to climate change. The CO2 released from the burned wood is not balanced by photosynthetic carbon fixation (storage) that would occur in new tree growth. Harvesting the forest may aso release carbon from the soil that would otherwise have remained buried in the A and B horizons.
Forests contain trees that absorb pollutants and store carbon dioxide. The cutting and burning of trees releases carbon dioxide and contributes to climate change. The CO2 released from the burned wood is not balanced by photosynthetic carbon fixation (storage) that would occur in new tree growth. Harvesting the forest may aso release carbon from the soil that would otherwise have remained buried in the A and B horizons.
The Role of Forest Fires
Though it may seem counter intuitive, forest fires are an important part of maintaining healthy forests. When you think of a natural forest, you likely imagine an area densely packed with lush trees and untouched by people. However, this is inaccurate; forests from a century ago were only loosely populated with trees.
This low density of trees was due to low-level forest fires. These naturally occurring forest fires would burn plants and vegetation around trees, sometimes scorching trees, but most often avoiding major destruction to the forest. The trees were not densely packed enough to allow for the destructive forest fires that we know today.
Forest fires maintain the health of forests. Some fire-tolerant varieties of trees rely on fires to spread their seeds. Their saplings then grow after the fire burns out. Without fires, these trees do not grow, leaving more room in the under story for fire-intolerant trees and brush. Lack of forest fires also provide potential for ladder trees to entwine larger trees. Ladder trees allow fire to grow up the bases of larger trees and start fires in the tree crowns and forest canopy. Forests also become more susceptible to disease without forest fires.
When people began to live closer to forests, a policy of fire suppression began. Humans would put out any fires, both natural and man-made. Fire suppression, combined with restrictions on deforestation has caused today’s forests to grow very dense. This high tree density brings an increased risk of destructive forest fires that endanger property and the forests themselves.
Though it may seem counter intuitive, forest fires are an important part of maintaining healthy forests. When you think of a natural forest, you likely imagine an area densely packed with lush trees and untouched by people. However, this is inaccurate; forests from a century ago were only loosely populated with trees.
This low density of trees was due to low-level forest fires. These naturally occurring forest fires would burn plants and vegetation around trees, sometimes scorching trees, but most often avoiding major destruction to the forest. The trees were not densely packed enough to allow for the destructive forest fires that we know today.
Forest fires maintain the health of forests. Some fire-tolerant varieties of trees rely on fires to spread their seeds. Their saplings then grow after the fire burns out. Without fires, these trees do not grow, leaving more room in the under story for fire-intolerant trees and brush. Lack of forest fires also provide potential for ladder trees to entwine larger trees. Ladder trees allow fire to grow up the bases of larger trees and start fires in the tree crowns and forest canopy. Forests also become more susceptible to disease without forest fires.
When people began to live closer to forests, a policy of fire suppression began. Humans would put out any fires, both natural and man-made. Fire suppression, combined with restrictions on deforestation has caused today’s forests to grow very dense. This high tree density brings an increased risk of destructive forest fires that endanger property and the forests themselves.
Fire Management
Human have followed a variety of management policies with respect to fire. For many years, managers of forest ecosystems, including the USFS, worked to suppress fires. This strategy led to the accumulation of large quantities of dead biomass on the forest floor, which built up until a large fire became inevitable.
Prescribed burn is a method by which forests are set on fire under controlled conditions in order to reduce the occurrence of natural fire. This method reduces the accumulation of dead biomass on a forest floor. Prescribed burns help reduce the risk of uncontrolled natural fires and provide some of the other benefits of fire. More recently, fire managers have allowed certain fires that have occurred naturally to burn. This policy appears to have been accepted in many parts of the United States, as long as human life and property are not threatened.
Human have followed a variety of management policies with respect to fire. For many years, managers of forest ecosystems, including the USFS, worked to suppress fires. This strategy led to the accumulation of large quantities of dead biomass on the forest floor, which built up until a large fire became inevitable.
Prescribed burn is a method by which forests are set on fire under controlled conditions in order to reduce the occurrence of natural fire. This method reduces the accumulation of dead biomass on a forest floor. Prescribed burns help reduce the risk of uncontrolled natural fires and provide some of the other benefits of fire. More recently, fire managers have allowed certain fires that have occurred naturally to burn. This policy appears to have been accepted in many parts of the United States, as long as human life and property are not threatened.
Methods for Mitigating Human Impact on Forests
In addition to prescribed burn, some of the methods for mitigating deforestation include reforestation, using and buying wood harvested by ecologically sustainable forestry techniques, and reusing wood. Methods to protect forests from pathogens and insects include integrated pest management (IPM) and the removal of affected trees.
In addition to prescribed burn, some of the methods for mitigating deforestation include reforestation, using and buying wood harvested by ecologically sustainable forestry techniques, and reusing wood. Methods to protect forests from pathogens and insects include integrated pest management (IPM) and the removal of affected trees.