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More on the science behind global warming

Global warming effects on Northwest fish and wildlife
By Jonathan Harrington

How are rising temperatures affecting Washington State's fish and wildlife? The water temperature in Lake Washington is rising at an alarming rate. Between 1962 and 2004, the lake temperature increased more than 1˚F, while air temperature rose more than 1.5˚F. Doesn’t sound bad does it? But remember what a degree or two difference did to the Northern Cascade's 2004–2005 ski season? (Puget Sound Action Team 2005).

The lake’s inhabitants are struggling to adjust to these abrupt changes. At the base of lake’s ecosystem is something called phytoplankton. Phytoplankton is a family of microscopic (algae) plants. As temperatures rise, phytoplankton bloom earlier each year. Another group of microscopic creatures that are near the base of the food chain, zooplankton, depend on phytoplankton blooms for their survival. The problem is that many zooplankton species have not been able to adjust to the earlier warming-induced bloom dates for the phytoplankton. This stunts their numbers and endangers the lives of other species up the food chain.

Phytoplankton algae love warmer temperatures. If phytoplankton blooms before predators such as zooplankton are around to keep their growth under control, then they can become so numerous that that they consume all oxygen and food in their path. They can also make people sick. Shellfish are vulnerable to algal blooming contamination. Toxic shellfish can cause domoic acid and paralytic shellfish poisoning. When blooms get out of control, fisheries often have to close, resulting in significant economic losses. The number of fishery closures in the Puget Sound area has increased significantly in recent years (Puget Sound Action Team 2005).

The Salmon’s Sad Fate
The effects of temperature change on creatures at the base of the food chain has ramifications for those higher up both in and outside the water, such as larger filter feeders, perch, trout, salmon, birds, and a large variety of mammals. Salmon runs provide a major source of protein for black and grizzly bears. Plummeting salmon populations often force bears to look elsewhere for food. In the Puget Sound area, the number of bear sightings in suburban neighborhoods is increasing. In parts of the Northwest where grizzly populations are prevalent, human attacks are on the rise. Talk show host David Letterman’s country home in Choteau, Montana, was invaded by an unwelcome grizzly prowler in 2003. Fortunately, no one was at home at the time (Hanson 2004).

There are seven prevalent species of salmon in the Puget Sound. Most are in precipitous decline. Salmon populations most affected by increasing temperatures live in stream and estuarine habitats. A combination of increased flooding, lower summer and fall stream flows, and higher temperatures increases their susceptibility to disease and disrupts their reproductive cycles. Most salmon species are vulnerable when water temperatures rise above 70˚F. Since 1974, temperatures in the main migratory route used by salmon moving from Lake Washington to the Puget Sound have risen. The number of days during which summer temperatures rose above 70˚F in this waterway have almost doubled (Puget Sound Action Team 2005).

No Place to Hide

Conditions are bad enough for migratory species that are stressed by higher temperatures but may have the ability to migrate to safer waters. However, what about species that cannot easily migrate to more favorable climes? The majority of plant and animal species that have recently become extinct or endangered are non-migratory. Also, many species that are capable of migrating are restricted from doing so because their habitats are surrounded by human development, such as suburbs, farmland, cities, and golf courses. If you look at a United States National Park Service map, one fact that immediately jumps out is how fractured and disconnected protected natural habitats really are. There are few natural corridors through which wildlife can migrate. Species that are acclimated to high mountain or island habitats are especially vulnerable (Thomas et. al. 2004). Many visitors to Hawaii are enamored by Waikiki Beach and its dozens of golf courses. However, many people do not know that Hawaii is also famous for having the most endangered species per square mile of any place on the planet. Given Hawaii’s geographic isolation, these species’ only hope for survival is lightning-fast adaptation [unlikely] or human-assisted relocation (Saunders and Maxwell 2005).

Essay written by Dr. Jonathan Harrington
Do not reproduce without expressed written permission from the author
2008 All rights reserved

 

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