LITE10_-_study_guide

LITE10_-_study_guide - Study Guide Chapter 10 Sustaining...

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Study Guide – Chapter 10 – Sustaining Terrestrial Biodiversity: The Ecosystem Approach The role of the gray wolf, a keystone species, was to cull herds of bison, elk, and mule deer. Reducing these herbivore populations helped control the destruction of vegetation and soil erosion. Wolves reduced the coyote populations by predation and direct food competition. From 1850-1900 the gray wolf population was reduced from 350,000 to several hundred by rancher, hunters, and government employees, and in 1974 the gray wolf was listed as endangered. In 1995-96, federal wildlife agents relocated 41 gray wolves from Canada to Yellowstone National Park. By 2007 the park had 171 gray wolves in 11 packs, making the gray wolf a relocation success story. Six of the packs travel outside the park at certain times of the year; this migration requires continued Endangered Species Act protection to keep them from being killed. Major Threats to Forest Ecosystems Forests cover 30% of the earth’s surface, excluding Greenland and Antarctica. Natural forests are categorized as old growth – a forest that has never been cut and without significant human disturbance, or secondary growth – a stand of trees resulting from ecological succession after human or natural removal. A tree plantation , a commercial tree farm, is a managed tract of uniform (age, species) trees harvested and replanted on a regular cycle. Tree plantations have far less biodiversity than either type of natural forest. Their purpose is to supply wood for paper mills and composite board production. The depletion of soil nutrients and use of genetically engineered species are problems managers and ecologist must address. Three-fourths of the world’s old growth forests are in Russia, Canada, Brazil, Indonesia, and Papua New Guinea. To protect old growth forest, tree plantations could be (and probably should be) established on already cleared land to provide the industrial wood demands of the world. Forests provide several ecological services, including: -Photosynthesis: forests remove CO 2 , helping to stabilize temperature and slow global warming -Medicines: both traditional and prescription -Habitat for 2/3 of the earth’s terrestrial species -Home to 300 million people One out of 4 people has a job that is dependent on forest productivity Unsustainable Logging: The first step in the tree harvesting process is developing a plan to build roads for access and timber removal. Roads can increase soil erosion, increase runoff to adjacent waterways, fragment habitats, allow invasion by pests and disease, and open inaccessible areas to human disturbance activities (e.g., off-road vehicles). Several methods can be used to harvest trees. Selective cutting removes intermediate and mature trees in an uneven-aged forest, whereas clear cutting removes all trees from an area. Clear cutting is the most cost effective way to log, BUT also the most destructive to ecosystems in terms of ecosystem services, wildlife habitat, and human aesthetic value (Figure 10-
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LITE10_-_study_guide - Study Guide Chapter 10 Sustaining...

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