Tree harvesting in the past meant the removal of all trees of any size and regardless of value. Logging companies clear-cut the landscape, which not only destroys the forest but also eliminates ecosystems. Even animals inhabiting the uncut adjacent forest must contend with the increased activity and noise coming from the clear-cutting zone. Clear-cutting also makes the harvested land vulnerable to soil erosion, floods streams, increases silt levels in streams that harm aquatic life, and makes landslides more likely.
During 2007 in Oregon, storms caused landslides in two clear-cut areas and torrents of mud and debris overwhelmed homes and vehicles and covered a state highway. While no humans were killed, several received injuries, and the damage to wildlife has not been fully resolved. Stephen Hobbs of the Oregon Board of Forestry described the event as a rare quirk of nature. He told the Oregonian, “Mother Nature threw a curveball at us. It was a pretty intense storm event, so you’re going to have unexpected things happen.” Despite these assurances, other people suspect that clear-cutting creates a danger to human and animal life. The University of Washington professor David Montgomery told the Olympian in 2008, “As a geologist, I see no surprises here. When you clear-cut potentially unstable slopes, you increase the risk of landslides up to tenfold.” These differences of opinion on the harm of clear-cutting and other tree harvesting methods continue.
In addition to the harvesting method loggers choose, all harvesting sites require roads built into the forest to give equipment access and allow logging trucks to transport the logs out of the forest. Roads help the overall efficiency of logging, and timber companies cannot do their job without them, but forest roads also harm ecosystems by fragmenting habitat, driving out animal species, and giving access to invasive species.
Once loggers reach the logging site, they can use any of a variety of harvesting methods, described in the table on the next page. Over the long term it is in the best interests of loggers to choose a method that sustains their industry but also conserves forests for future generations.
Logging comprises any of the harvesting methods described in the table below, plus the methods used for felling the trees and the yarding methods for taking the logs out of the forest. Tree cutting can be done in two ways: conventional sawing or mechanical logging. Sawing cuts the full length of trees to the stump close to the ground, while mechanical cutting removes trees using a piece of equipment called a feller (or faller). An operator drives a feller up to the tree to be removed and a blade or saw at the end of the feller’s arm cuts the tree, usually leaving a taller stump than the sawing method.
For centuries, horse-drawn wagons hauled logs out of the forest. This required little road-building and made little noise. In the 1800s horse or oxen teams dragged logs to specialized narrow logging railroads or, in areas where railroads could not reach, to mountain streams where workers transferred the logs to another conveyance, a process called offloading. Gravity simply carried the harvest downstream to a collection point at the bottom of the mountain. Dragging logs downhill to a train or stream soon proved to be inefficient because every forest snag or stump acted as a fishhook and grabbed at each log on the journey. Loggers soon learned that dragging logs uphill by cable to a mountaintop railroad track was the best approach. This so-called uphill logging or skyline logging evolved into the helicopter logging used by many timber operations today in difficult-to-reach terrain. Though horses still haul timber in parts of the world, today most operations use trucks, cables, and helicopters.
Timber harvests consist of whole logs, called roundwood, which means logs denuded of branches and bark. These harvests are of three main types: (1) hardwoods from broadleaf, deciduous trees; (2) softwoods from gymnosperm trees, including pine, spruce, fir, and juniper; or (3) pulpwood, which is any wood harvested for papermaking.
Source of Information : Green Technology Conservation Protecting Our Plant Resources