Who Will Protect the Web of Life?/The Intricate Web of Life

Vanishing Variety 

Sadly, despite the beauty and variety of life forms, a number of researchers say that man is pushing species to extinction at an alarming rate. In what way? 

* Habitat destruction.  This ranks as the leading cause of extinction. It includes logging, mining, clearing trees for cattle, and building dams and highways where wilderness once existed. As ecosystems shrink, species lose the resources  they need to survive. Natural environments are fragmented, degraded, and eliminated.  Migration routes are disrupted. Genetic diversity diminishes. Local populations of living things can  not rebound from disease and other stresses. Hence, one by one, species gradually die out.

The extinction of certain species can even trigger a chain reaction of extinctions, for when one part of the web of life is eliminated, others can be affected-such as pollinators-can affect a myriad of other species. 

* Introduced species. When humans introduce a foreign species into an ecosystem, that species may take over niches that other species have occupied.  the foreign species might also indirectly  change the ecosystem enough to force out native species, or it might bring with it diseases to which the natives have no immunity.  Especially on islands, where species have long existed in isolation and have not dwelt  with newcomers, the original inhabitants may be unable  to adapt and survive. 

A typical example is a "killer" alga. Cauterpa taxifolia, which is destroying other marine species in the Mediterranean Sea. Introduced accidentally off the coast of Monaco, it has now begun to spread on the seabed. It is toxic, and it has no known predators.  "We could be seeing the beginning of an ecological catastrophe," says Alexandre Meinesz, professor of marine biology at the University of Nice, France. 

Next time: Who Will Protect the Web of Life?/ The Intricate Web of Life -Conclusion of Vanishing Variety

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