Why forestry is bad

In fact, it is common practice to manage the post-harvest succession to speed up the rate of regeneration of trees. This allows the next harvest to be made after a relatively short time, so more profit can be made. This period of time is known as a harvest rotation. In this sense, forestry as it is usually practised does not result in a net deforestation, and if appropriately managed the forest resource is not depleted.

Even though hundreds of thousands of hectares are harvested each year in Canada thousand ha in , the net deforestation is essentially zero Table Timber harvesting can be viewed as a disturbance of the forest ecosystem, followed by regeneration.

Additional disturbances are associated with silvicultural activities, such as preparing the site for planting, thinning dense stands, and applying herbicide or insecticide to deal with pest problems. Silviculture, the branch of forestry that involves tending and growing forests, is practised over an extensive area in Canada.

Some planted areas are managed intensively to develop a plantation, which is an anthropogenic forest, but one that lacks many of the ecological and aesthetic values of natural forest. In this chapter we examine some of the ecological effects of timber harvesting and silviculture, with a focus on site quality, hunted animals, and biodiversity.

Additional effects of forestry are examined in other chapters: pesticide spraying in Chapter 22, implications for carbon storage in Chapter 17, and tropical deforestation and global biodiversity in Chapter In Chapter 14, we defined site capability or site quality as the potential of land to sustain the productivity of agricultural crops. This is also relevant to forestry, in terms of the ability of land to sustain the productivity of trees. Site capability is a complex attribute that involves the amounts of nutrients and organic matter in soil, the availability of moisture, and other factors affecting plant growth.

These factors are influenced by soil type, climate, drainage, rate of nutrient cycling, and the kinds of plant and microbial communities that are present. The ability of soil to supply plants with nutrients is a critical aspect of site capability.

In large part, this ecological function depends on the nutrient capital of a site, which is the amount of nutrients present in the soil, living vegetation, and dead organic matter. When trees are harvested, the nutrients in their biomass are also removed, which can deplete the nutrient capital of the site. A stand of forest may be harvested using a variety of methods, which vary in the amount of biomass and nutrients that are removed from the site.

The most intensive harvest is a clear-cut, in which all economically useful trees are removed. The smallest clear-cuts, typically involving a hectare or less, are known as a group-selection harvest. More typically, clear-cuts entail the harvesting of trees from larger areas, on the order of ha. The largest clear-cuts may extend over hundreds, and even thousands, of hectares. However, such extensive operations are unusual, and are usually associated with the salvaging of trees that have been damaged by a wildfire, windstorm, or insect infestation.

There are also some less intensive methods of clear-cutting. A shelterwood harvest is a staged clear-cut, in which some larger trees of economically desirable species are left standing during the initial cut.

These provide a seed source and a partially shaded environment that encourages natural regeneration. A strip-cut is another kind of staged harvest, in which long and narrow clear-cuts are made at intervals, with uncut forest left in between to provide a source of seed to regenerate trees in the cut strips. Once the regeneration is established, another strip-cut is made, again leaving intact forest on one of the sides.

This system of progressive strip-cutting continues until all the forest in the management block the specific area being managed this way has been harvested. Typically, an area is harvested in three to four strips. To regenerate trees on the final strips, foresters may rely on advanced regeneration — that is, on small individuals of tree species that existed in the stand prior to harvesting and that survived the disturbance of clear-cutting.

Alternatively, they may plant the last strip with seedlings. Image This photo shows a three-year-old shelterwood cut of hardwood forest in Nova Scotia. This treatment produces a complex habitat that supports a mixture of birds and other wildlife typical of both clear-cuts and mature forest. Source: B. Clear-cutting systems also vary in how intensively the biomass of individual trees is harvested. The harvested logs can then be processed into lumber or pulp for manufacturing paper.

A whole-tree harvest is more intensive because it removes all of the above-ground biomass of the trees, including the branches and foliage. This intensive kind of harvest will recover considerably more biomass than a stem-only cut, which is an advantage if the wood is to be used as a source of bio-energy. Although intensive harvests such as a whole-tree clear-cut increases the yield of biomass, there is also considerably more removal of nutrients. Some forest scientists have suggested that the nutrient removals from whole-tree harvests could degrade the capability of sites to sustain tree productivity.

The problem would be especially severe if the harvests are conducted over a short rotation. This might not allow enough time for the nutrient capital to recover by natural inputs, such as by precipitation, nitrogen fixation, and weathering of minerals Figure Figure Diagram a suggests that a relatively long rotation can allow harvested nutrients to be replenished by natural inputs through rainfall, weathering of minerals, nitrogen fixation, and other means.

An adequate post-harvest recovery means that harvesting is sustainable with respect to the nutrient capital of the site. Under the shorter rotation dashed line , the harvested nutrients are not totally replenished between successive clear-cuts, resulting in a degradation of nutrient capital. Site capability can also be degraded by an increase in the intensity of the harvest. This is illustrated in diagram b , in which a whole-tree clear-cut removes twice as much nutrient as a stem-only harvest.

Diagram c indicates that fertile sites solid line are less likely to be degraded by intensive harvests over short rotations, compared with less fertile sites dashed line. Source: Modified from Kimmins Site impoverishment caused by intensive cropping is a well-known problem in farming, in which severely degraded land may have to be abandoned for some or all agricultural purposes.

However, usually this problem can be managed, to a degree, by applying fertilizer or composted organic matter to the land. Sometimes, however, the degradation of site capability, especially of tilth, is too severe, and this simple mitigation is not successful.

Of course, the harvest rotation in agriculture is usually annual, whereas in forestry it ranges from about 20 to years. However, each timber harvest involves the removal of a huge quantity of biomass, and thus of nutrients. Compare, for example, the amounts of biomass and nutrients removed by clear-cuts of a conifer forest in Nova Scotia Table The increased yield may be an advantage, particularly if the harvest is to be used for energy production. The increased harvest of biomass is, however, due to the removal of nutrient-rich tissues such as foliage and small branches.

Consequently, the whole-tree harvest removed up to twice as many nutrients as did the stem-only clear-cut. Table This study involved weighing the biomass harvested by a a stem-only clear-cut and b a whole-tree clear-cut each 0. Nutrient concentrations were determined in subsamples of the biomass and were used to calculate the amounts of nutrients removed.

Source: Data from Freedman et al. Unfortunately, there are few studies that allow foresters to compare the productivity of subsequent harvest rotations on the same site. Such studies would take more than years, requiring several generations of foresters!

Therefore, it is difficult to evaluate the implications of nutrient removal by clear-cutting. Overall, however, it appears that a degradation of site nutrient capital is a less severe problem in forest harvesting than in agriculture. Consequently, nutrient removals by timber harvesting should be viewed as a potential long-term problem. Because forestry is an economically important activity, and the maintenance of site capability is critical to the sustainability of the enterprise, scientists should continue to study the effects of harvesting on nutrient capital.

In the short term, however, forestry causes more immediate kinds of damage to site capability and biodiversity that deserve our attention. The disturbance of forested land can increase the rate at which dissolved nutrients are transported downward into the soil with percolating rainwater a process known as leaching. Eventually, leached nutrients can find their way into groundwater and surface waters. The nutrients with the greatest tendency to leach are nitrate and potassium, both of which are highly soluble in water.

However, calcium, magnesium, and sulphate may also leach in significant amounts. Of course, following a clear-cut, any nutrient losses by leaching are in addition to that removed with tree biomass. A well-known study of nutrient leaching caused by forest disturbance was done at Hubbard Brook, New Hampshire. This large-scale experiment involved felling all of the trees on a ha watershed, but without removing any biomass — the cut trees were left on the ground.

The watershed was then treated with herbicide for three years to suppress regeneration. This experiment was designed to examine the effects of intense disturbance, by de-vegetation, on biological control of watershed functions such as nutrient cycling and hydrology. The research was not intended to examine the effects of a typical forestry practice. The losses were much larger than from an undisturbed reference watershed: 4. The increased streamflow was caused by the disruption of transpiration from plant foliage.

However, increases in nutrient concentration in the streamwater were more important: during the first three years, NO 3 increased by an average factor of 40; K, by 11; Ca, by 5.

The losses of N, Ca, and Mg in the streamwater were similar to their amounts in the above-ground biomass of the forest. Nutrient Losses in Streamflow after Deforestation. The experimental watersheds are located at Hubbard Brook, New Hampshire.

The data are for the first three years following deforestation of a ha watershed, compared with an uncut reference watershed of similar size. Losses are stated in kilograms per hectare per three-year period.

Source: Modified from Bormann and Likens Because this experiment in de-vegetation did not involve a typical forestry practice, the measured effects are unrealistically large. However, watershed-level studies of clear-cutting have also found an increase in nutrient leaching, although to a lesser degree than that caused by the de-vegetation at Hubbard Brook.

However, other studies have found smaller effects of clear-cutting on nutrient losses with streamflow, especially if only a portion of the watershed was cut.

Nitrate and other highly soluble ions are leached from watersheds after clear-cutting and after other disturbances, such as wildfire for several reasons. First, disturbance stimulates the activity of microbes involved in the decomposition of organic matter. This occurs because removal of the tree canopy results in warming of the forest floor and surface soil, and decreased uptake by plants leads to an increase of soil nutrients and moisture. Second, disturbance often stimulates the microbial processes of ammonification and nitrification see Chapter 5 , resulting in increased rates of production of nitrate, which is extremely soluble and readily lost from soil.

Forestry activities can cause severe losses of soil, or erosion, particularly in terrain with steep slopes. In most cases, erosion is triggered by improperly constructing logging roads, using streams as trails to haul logs, running log-removal trails down slopes instead of along them, and harvesting trees from steep slopes that are extremely vulnerable to soil loss.

In general, however, road building is the most important cause of erosion on forestry lands, especially where culverts channelled stream crossings are not sufficiently large or numerous, or are poorly installed. Severe erosion causes many environmental damages. In extreme cases, the loss of soil may expose bedrock, making forest regeneration impossible.

Soil loss also represents a depletion of site nutrient capital. Erosion also causes secondary damage to aquatic habitats, including the deposition of silt or siltation , which covers gravel substrates that are important to spawning fish.

Also, the shallower water increases the risk of flooding. However, in many cases erosion is a largely avoidable environmental effect of forestry. The irresponsible practices that can cause erosion are restricted by provincial regulations and occur much less frequently now than in the past. Practices that help to reduce erosion include the following:. It has become a common practice to leave strips of uncut forest beside streams, rivers, and lakes.

These buffer zones greatly reduce the erosion of streambanks, eliminate temperature increases in the water, maintain riparian lake- and stream-side habitat for wildlife, and mitigate some of the aesthetic damage from forest harvesting. While it is widely accepted that riparian buffers provide important benefits, there is no consensus about how wide the uncut strips should be.

This is an economically important consideration, because large areas of valuable timber are withdrawn from the potential harvest when buffer strips are left. In some cases, selective harvesting of trees may be allowed within riparian buffers, as long as this does not compromise the ecological services provided by these special management zones.

The cover of forest on a watershed has a strong influence on its hydrology. Large amounts of water are evaporated into the atmosphere by vegetation, especially by trees because they have so much foliage this is transpiration; evapotranspiration includes evaporation from non-living surfaces. In the absence of transpiration, an equivalent quantity of water would leave the watershed as streamflow or as seepage to deeper groundwater.

The hydrologic budget of watersheds is extremely seasonal, particularly in the temperate and boreal climates that are typical of forested regions of Canada. Evapotranspiration is highest during the growing season, which results in relatively sparse riverflow. Runoff is greater during late autumn and early winter, when there is little transpiration because deciduous trees have dropped their foliage, and even conifers are in a quiescent state.

However, much of the precipitation during that period recharges groundwater storage, which had been depleted by the uptake of water by vegetation during the summer. Runoff is greatest during the spring, when the accumulated snowpack melts, and that results in a spate of riverflow. Water inputs from incident precipitation IP into the km 2 watershed, and riverflow RF from the watershed, are displayed as monthly averages for the period Source: Modified from Freedman et al.

Disturbances such as wildfire and timber harvesting alter the hydrology of watersheds. The seasonality and amounts of flow can change, and erosion and flooding may occur downstream.

Some poorly drained sites may become wetter, because reduced transpiration can raise the water table. In general, the increase in streamflow is related to the proportion of the watershed that was disturbed.

The increase is proportionately less after partial cuts. Clear-cuts usually regenerate quickly, and in some cases the vigorous regrowth of shrubs and herbs can restore most of the original foliage area in as few as four to six years.

Consequently, the biggest increases in streamflow occur in the first year after cutting, followed by rapid recovery to the pre-harvest condition. In the temperate and boreal climates prevalent in much of Canada, the largest increases in streamflow occur during the late spring, summer, and early autumn, these being the seasons when transpiration is most important.

Hydrology can also be affected by a change in the type of forest that is dominant on a watershed. For example, if an area of hardwood forest is converted into conifer plantations, the annual streamflow may decrease. This happens because the conifers maintain their foliage throughout the year, and so extend the transpiration season into times when angiosperm trees lack foliage. Clear-cuts usually regenerate rather quickly.

Initially, however, most of the regenerating biomass involves plants other than the tree species that foresters consider desirable. As a result, the vigorous regrowth is often regarded as being detrimental to silvicultural objectives.

However, a rapid re-vegetation of clear-cuts and other disturbed lands does provide important ecological benefits. They re-establish a measure of biological control over nutrient cycling, erosion, and hydrology, while also restoring habitat for animals.

For example, during the first few years after clear-cutting, fast-growing vegetation restores a high rate of nutrient uptake from the soil. Eventually, the early successional plants die, and their nutrients are recycled by decomposition and made available to trees. In addition, the re-vegetation restores habitat for birds, mammals, and other wildlife. Clearly, the early reorganization phase of succession is enhanced by the rapid regeneration of many plant species, including those considered to be weeds by foresters.

Clear-cutting and other forestry practices inflict intense disturbances on forests. They cause dramatic changes in the habitat available to support plants, animals, and microbes, as well as their various communities. Some species benefit from habitat changes that occur because of forestry, but others suffer damage.

In the following sections, we examine the effects of forestry on aspects of Canadian biodiversity — the richness of biological variation in our country. The effects of clear-cutting on plants, mammals, birds, and fish will be examined because these groups are relatively well studied and are considered to be important by our society. Non-commercial sources of forest depletion include removal for agriculture pasture and crops , urban development, droughts, desert encroachment, loss of ground water, insect damage, fire and other natural phenomena disease, typhoons.

In some areas of the world, particularly in the tropics, rain forests, are covering what might be considered the most valuable commodity - viable agricultural land.

Forests are burned or clear-cut to facilitate access to, and use of, the land. This practice often occurs when the perceived need for long term sustainability is overwhelmed by short-term sustenance goals.

Not only are the depletion of species-rich forests a problem, affecting the local and regional hydrological regime, the smoke caused by the burning trees pollutes the atmosphere, adding more CO 2 , and furthering the greenhouse effect. Of course, monitoring the health of forests is crucial for sustainability and conservation issues. Depletion of key species such as mangrove in environmentally sensitive coastline areas, removal of key support or shade trees from a potential crop tree, or disappearance of a large biota acting as a CO 2 reservoir all affect humans and society in a negative way, and more effort is being made to monitor and enforce regulations and plans to protect these areas.

International and domestic forestry applications where remote sensing can be utilized include sustainable development, biodiversity, land title and tenure cadastre , monitoring deforestation, reforestation monitoring and managing, commercial logging operations, shoreline and watershed protection, biophysical monitoring wildlife habitat assessment , and other environmental concerns. General forest cover information is valuable to developing countries with limited previous knowledge of their forestry resources.

Canadian requirements for forestry application information differ considerably from international needs, due in part to contrasts in tree size, species diversity monoculture vs.

The level of accuracy and resolution of data required to address respective forestry issues differs accordingly. Canadian agencies have extensive a priori knowledge of their forestry resources and present inventory and mapping needs are often capably addressed by available data sources. For Canadian applications requirements, high accuracy for accurate information content , multispectral information, fine resolution, and data continuity are the most important.

Farming, grazing of livestock, mining, and drilling combined account for more than half of all deforestation. Forestry practices, wildfires and, in small part, urbanization account for the rest. In Malaysia and Indonesia, forests are cut down to make way for producing palm oil , which can be found in everything from shampoo to saltines. In the Amazon, cattle ranching and farms—particularly soy plantations—are key culprits. Loggers, some of them acting illegally , also build roads to access more and more remote forests—which leads to further deforestation.

Forests are also cut as a result of growing urban sprawl as land is developed for homes. Not all deforestation is intentional. Some is caused by a combination of human and natural factors like wildfires and overgrazing, which may prevent the growth of young trees. Deforestation affects the people and animals where trees are cut, as well as the wider world. That disruption leads to more extreme temperature swings that can be harmful to plants and animals.

Yet the effects of deforestation reach much farther. The South American rainforest, for example, influences regional and perhaps even global water cycles, and it's key to the water supply in Brazilian cities and neighboring countries. The Amazon actually helps furnish water to some of the soy farmers and beef ranchers who are clearing the forest.

In terms of climate change, cutting trees both adds carbon dioxide to the air and removes the ability to absorb existing carbon dioxide. If tropical deforestation were a country, according to the World Resources Institute , it would rank third in carbon dioxide-equivalent emissions, behind China and the U.

The numbers are grim, but many conservationists see reasons for hope. A movement is under way to preserve existing forest ecosystems and restore lost tree cover. In addition, forest roads give people easy access to previously remote areas. The result is increased disruption of forest ecosystems by human activities such as littering, hunting, and the release of exhaust fumes from ATVs, which themselves cause a significant amount of ecological damage.

Pulp and paper mills discharge waste water effluent into waterways which may expose aquatic life to harmful chemicals. Research in indicated the Corner Brook mill discharged effluent into the Humber Arm which contained wood fibres that smothered organisms living on the bottom.

In , Kruger admitted that it released harmful toxins into Humber Arm. It also built a secondary treatment plant to reduce solid wastes in its effluent. Paper mills also emit greenhouse gases and other pollutants. Kruger has built air sampling stations near its Corner Brook mill to detect emissions that exceed provincial standards.

All users of Newfoundland and Labrador forests — whether they are large multinational corporations, small local companies, or private residents — must adhere to government regulations stipulating how, where, and in what quantities wood may be cut. Central to the province's forest management is the Forestry Act, which requires that all forest resources must be harvested in a sustainable manner.

The provincial government has divided the province into 24 management districts — 18 on the island and six in Labrador. The Forest Resources Branch issues an annual allowable cut AAC for each district, a quota which seeks to establish the maximum number of trees that can be harvested in a given year without depleting the resource.