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Habitat Destruction

An organism's habitat is where it gets its food and water, finds its shelter and receives what it needs to survive. Destruction of a species' habitat, changes how that species can survive. Habitat destruction can force species to move elsewhere or go extinct, and can disrupt the whole community that lives in that area. Some scientists believe that habitat destruction is the primary reason why biodiversity is being lost. Logging old-growth forests, damming rivers, filling in wetlands, and overgrazing cattle on prairies are all examples of habitat destruction.

Although old-growth logging no longer occurs in any of the national parks, historic logging has had a large influence on shaping park environments. Previously logged areas are not able to grow back to the same forest they used to be if new species have been introduced. This is a problem in Redwood National and State Parks where old-growth redwoods were historically logged and the sites were replanted with Douglas-fir. Forests develop slowly and after an old-growth forest has been logged, the new trees that emerge are called a second-growth forest. These trees typically do not have the same structure, composition, or density as a true old-growth forest, therefore they are often not ideal for wildlife to use. Certain animals such as the northern sported owl, the marbled murrelet, the fisher, and martin depend on old-growth forests as their habitat, and without it their populations decline and disappear.

Logging on lands adjacent to national parks causes the separation of large continuous habitats into isolated and small patches of forests or fragments. Fragmentation limits ranges of wildlife that depend on continuous habitats to live in. This is a concern at Oregon Caves and Lassen Volcanic where logging on surrounding lands is causing an “edge effect.”  The edges of any habitat are never straight lines, but change in width and depth depending on the environment. When logging occurs it creates an unnatural edge, inviting unwanted invasive species to enter in and eliminate natural structural diversity. Edges have been shown to negatively affect many nesting birds causing their nests to be much more vulnerable to predators. Both destruction and fragmentation of forests negatively affect biodiversity by reducing the number of organisms that can live in the environment.

 

Marbled Murrelet

One such animal dependent on intact old-growth forests is the Marbled Murrelet. This seabird spends most of its time in the water but uses old-growth coastal forests to nest in. Marbled Murrelet populations have been declining and were added to the Endangered Species List in 1992. They are not one of the most colorful looking birds you’ve ever seen but they are unique in their behavior. These birds have been difficult to study because of secretive nesting behavior. They fly fast, up to 158 km/h, and enter their nests at dusk making it difficult to know exactly where they breed. Once in a tree they can easily go from one limb to another in search of the perfect nesting spot. While at sea, marbled murrelets spend time swimming and diving for food. They are known to dive to depths of 50 meters and eat mostly small fish. The greatest threat to this species is habitat loss from logging and human development that encroaches on old growth where they nest. Eliminating their nesting habitat has a direct impact on the success of these birds. Another threat to Marbled Murrelets is nest predation by various aboreal predators, particularly jays and ravens.  

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