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
– a forest that has never been cut and without significant human
– a stand of trees resulting from
human or natural removal.
, 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
, 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
The first step in the tree harvesting process is developing a plan to build roads for access and
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.
removes intermediate and mature trees in an uneven-aged forest, whereas
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-