Written by Miranda Huey
|Monday, 22 June 2009|
Clearcutting has a major environmental impact on the water cycle. Since trees trap water and topsoil, cutting them down increases the risk of flooding. When it rains, the water and topsoil run over land down to rivers, turning them brown, creating areas of excess nutrients in the sea.1 One country that has been greatly affected by deforestation induced flooding is North Korea, where state policy for decades was to clearcut to convert forests into farmland. As major areas were cleared, rains destroyed roads, power lines, and agricultural fields. Even after they adopted a policy of reforestation in 1994, the floods have continued to devastate neighboring farmland and led to massive famines in the country.2
Another unfortunate victim of clearcutting has been the local wildlife living in the forest ecosystem.3 Clearcutting essentially demolishes entire habitats, and makes the habitats more vulnerable in the future to damage by insects, diseases, acid rain, and wind.4 In addition to wildlife victims, clearcutting can contribute to problems for ecosystems that depend on forests, like the streams and rivers which run through them. Clearcutting prevents trees from shading riverbanks, which raises the temperature of riverbanks and rivers, contributing to the extinction of some fish and amphibian species. Because the trees no longer hold down the soil, river banks increasingly erode as sediment into the water, creating excess nutrients which exacerbate the changes in the river and create problems miles away, in the sea.5
Clearcutting is also a major contributor to global warming.6 When a tree trunk gets cut down, the crown, wood debris, and vines are left in the forest to decompose, which releases carbon dioxide. To compound the problem, sawmills can only make use of 30-40% of the wood put into them, and the other 60-70% of the wood becomes sawdust and scrap, which again decomposes into carbon dioxide.7 Clearcutting releases even more greenhouse gases into the atmosphere than forest fires.8 To make matters worse, after clearing, the remaining scrub and brush are sometimes burnt in large burn piles, directly polluting the atmosphere with particulate matter.9
However, as paradoxical as it may sound, clear-cutting has also been scientifically accepted as a legitimate way to regenerate forests in some cases, if done properly. For example, in Massachusetts, most of the original forests have already been cut down, and are now plantations of non-native species like Norway spruce and red pine. Clearcutting can remove any overcrowded or dying plantations and replace them with native trees which are more suitable to the local wildlife and environment.10 In native forests, clearcutting is one of the most effective ways to eliminate a prevalent disease.11
There are some alternatives to clearcutting. Selective cutting has been touted as a sustainable alternative to clearcutting. As defined by the USDA Forest Service in 1940, “selective cutting” means the thinning of forest from overmature and partially defective trees, in order to allow the middle-aged, healthiest trees to grow the best.12 For example, partial cutting prevents conifers from overpopulating and hindering other growth which usually occurs after clearcutting.13
However, many times, “selective cutting” has been used to remove high-grade, economically valuable trees, leaving behind the older, less healthy trees.14 In the Amazon forest, this has become a real problem. Not only are the largest, healthiest hardwood trees cut down, but for every tree cut down, up to 30 neighboring trees can be damaged because the vines connecting the trees together will pull them all down as one falls. In fact, one of the biggest problems is that selective cutting can soon lead to clearcutting. Heavy foresting tractors imprint deep soil tracks leading into the forest, which become makeshift roads for others to move in and continue the deforestation process.15
Both loggers and environmentalists are on the hunt for sustainable alternatives, and have come up with a variety of methods. One method, the agricultural replanting of trees after clearcutting, is good for reforesting quickly, but costs more for the logger16 and can significantly reduce the biodiversity of the forest. Shelterwood logging is a method of clearcutting in stages,17 which allows for a more gradual regrowth of trees of different ages.18 However, environmentalists dislike this option because it still results in the same ecological damages as clearcutting, just at a more gradual speed.19 Loggers dislike this option, since it requires multiple cuttings, and repeat trips.20 Another method is seed-tree logging, where the loggers leave behind some of the best trees in the area so that the forest can reseed itself. While this can reduce the impact on the ecosystem, in other cases, it can still disturb the ecosystem enough to kill the trees intended to be left alone.21 Additionally, even when some trees are left behind successfully, the ecosystem can end up growing species much different than those originally there.22
Therefore, both environmentalists and loggers are correct. Clearcutting has some pretty environmentally damaging effects, but in a few cases, it can also help the environment. In the cases when it doesn't, there have also been some sustainable alternatives, but even these are not always efficient or even sustainable. The real answer, it seems, will require both forestry expertise and thoughtful judgment to balance the needs and capacity for disruption of both the local forest ecology and of the logging industry which depends on it.
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