Only about one third of earth’s forests are untouched by humans. Even when disturbed areas are reforested, many do not support the same species as those which originally inhabited the area (Stokstad, 2008). Between 1960 and 1990, 20% of all the earth’s rainforests were cut.  During this time period, Asia lost 1/3 of its forests.  Since 1980, 80% of the Amazon rainforest has been cut and 100 square kilometers of Amazon rainforest is cut each year,  About fifty acres of rainforest are cut each minute globally. Forests cover 4 billion hectares, about 30% of earth’s land surface. Seven million hectares are lost each year, mostly in countries near the equator. Three million hectares are lost annually from Brazil alone (Sukumar, 2008).

     Islands frequently carry species that occur nowhere else in the world.  For example, of the 135 birds that occurred only in Hawaii, 101 are already extinct, 24 more are in danger.  The majority of the 161 birds which have become extinct have been island species.

     About 140,000 square kilometers of tropical rainforest are cut/year.  During the 1990s, the earth’s forest cover decreased by 4% and about half of the world’s forests have been lost since the dawn of agriculture.  More than half the earth’s wild wetlands have been lost during the past century.

     Due to population growth alone, the percentage of species in an average nation is expected to rise to about 7% by the year 2020 and 14% by 2050.  Human population growth is a primary factor in an estimated 88% of the species whose condition is considered threatened (McKee, 2003).

Habitat fragmentation can stress amphibian populations by increasing the distance between adult habitats and breeding areas (Becker, 2007). Many animals which inhabit deep woods habitats are threatened when a habitat is fragmented, not only because the physical area that they can inhabit is reduced, but also because new species are introduced into the area which compete with them. This is especially evident in the case of brown-headed cowbirds.

The brown headed cowbird parasitizes other birds by laying its eggs in their nests. Other birds raise the cowbirds as their own and the cowbird nestlings outcompete those of the other species. This brood parasitism can decrease the populations of songbirds by half. The brown headed cowbird originally inhabited western North America but expanded its populations eastward when forests were cleared. They prefer edge habitats so that the splitting of a large region of continuous forest into smaller habitats drastically increases the effect of cowbirds on forest birds.

EXTINCTION

Extinction is a natural process; it is estimated that over 99.9% of all the living things that have ever existed in earth's history are now extinct.  Sometimes extinction occurs at a slow rate; there are other times known as mass extinctions.

Due to the human impact on the natural world, it is estimated that at least 100 species become extinct every day; at this rate, the mass extinction through which we are now living will soon (by the year 2000?) surpass the Cretaceous extinction and become the 2nd largest in earth's history.

Why aren’t you aware of the species which become extinct every day?

1)     They are Rare:

--Look at the list of endangered species in New York State and those species which only exist in a few states.  How many of those have you heard of?

2)     Most people are unfamiliar with many groups of organisms, such as insects, freshwater mollusks, etc.  Ninety-five percent of all animal species are invertebrates and therefore many species could go extinct from your area without your being aware of them ever existing.

3)     Since most of the species on earth do not even occur in the U.S., most of the extinctions are not occuring in the U.S.  Two thirds of earth’s plant and animal species live in the tropics; many of which have yet to be discovered.  Island species are particularly vulnerable to extinction.

2)     Many U.S. species have already become extinct

     There are a number of organisms on the Endangered Species List that have not been seen in years/decades and may already be extinct such as the turgid blossom, yellow blossom, little Mariana fruit bat, Mariana mallard, scioto madtom.  The Bachman’s warbler and Ivory billed woodpecker are extinct from the U.S. but small populations still survive in Cuba. 

     Some species that inhabited New York in the past several hundred years have become completely extinct: these include Passenger Pigeon, Eastern Bison, sea mink, heath hen, Townsends Finch, and the Eastern Wapiti (a deer).  Other species have become extinct from other parts of the U.S. including the badlands bighorn sheep, Oregon bison, Carolina parakeet, Florida wolf, and long-eared kit fox.