TOPICS IN BIODIVERSITY LOSS
 
Does Biodiversity Change? Is Biodiversity Changing Now? Biodiversity Loss and Humans
Future for Biodiversity What if Loss Occurs? What Can Be Done? Biodiversity Hotspots
     
  ECOSYSTEMS  
     
 
     
 

Rainforests are experiencing biodiversity loss at rates greater than most other habitat types. The primary cause of rainforest loss is deforestation for timber, cattle grazing, and farming. Over 200,000 square miles of the Amazon rainforest have already been lost to deforestation, with another 7-10,000 square miles being destroyed each year. Scientists have only studied a fraction of the plants, animals, and insects that live in the rainforests, and estimate that there may be thousands of species not known to science at all. We have almost certainly driven to extinction already many species that we will never know about.

Another cause of rainforest biodiversity loss is climate change. Rainforests are delicately balanced ecosystems that can be substantially affected by even small changes in climate. The first documented victim of climate change in a rainforest was the Golden Toad (see below).

 
     
     
 

Wetlands are another habitat being lost at great pace. In the 1600s, the United States is estimated to have had approximately 220 million acres of wetland; in 1997, it had 105 million acres, less than half as many. The majority of those lost were drained, filled, and converted to other uses, such as farmland and later, parking lots.

Wetlands are very important to humans for a number of reasons, including storm mitigation and water filtration. Marshes and swamps serve as barriers when storms such as hurricanes come through, substantially decreasing wind speeds and absorbing storm surges. And all wetlands filter fresh water that runs through them, removing pollutants and making it safe for human consumption.

 
     
     
 
Coral reefs are extremely sensitive to changes in ocean temperature, and “coral bleaching” results when temperatures get too high; this phenomena will eventually kill corals if the temperature does not return to suitable levels. As of 2004, 20% of the world’s coral reefs were effectively dead, with no prospect of recovering. Research indicates that much of this destruction is due to human activity, including rising sea water temperatures.
 
     
  SPECIES  
     
   
         
The Baiji, or Chinese River Dolphin, was a species of freshwater dolphin that lived only in a 1000-mile stretch of China’s Yangtze River. Increased human use and pollution of the river degraded its habitat to the extent that a 2006 search yielded no trace of the animal in the river, and it has been declared functionally extinct. It is the first cetacean (the mammal family including dolphins and whales) member to have gone extinct because of humans.
 
The Golden Toad (Bufo periglenes) was a small, brightly colored toad that was abundant in the rain forests of Costa Rica. It has been extinct since 1989, when human-induced climate change altered the moisture regime of its habitat sufficiently to inhibit successful breeding.
 
Polar bears are one of the most well-known victims of climate change. Although they are not yet extinct, they are listed as vulnerable because their habitats are threatened by changing climates. Polar bears depend on a combination of land and sea ice to survive, and climate scientists estimate that as this sea ice melts because of global warming, the polar might could be extinct by the end of this century.
     
 
  GlossaryResourcesAcknowledgements  
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