The existence of a species is intimately linked to the habitat in which it lives, or perhaps more accurately the ecosystem of which it is a part. Thus changes in the ecosystem can have serious implications for the continued health of a species.

Extinction

Accurate recording of extinction numbers can be difficult, the vast majority of species have not yet been described and it therefore likely that some will disappear before they are even known to science. Species are generally not declared to be extinct until 50 years after they have last been seen, so figures for documented extinctions are probably conservative. Estimating rates of extinction is therefore also difficult and some species whose populations are reduced by habitat loss below the level necessary for long-term survival may hang on for several decades without hope of recovery as their population dwindles.

Evidence of extinction, especially of distinct populations of species, is however unfortunately fairly easy to find. In 1990, the otter died out in the Netherlands, and in 1991 Britain declared the mouse-eared bat extinct. In the past decade, at least 34 species or unique populations of plants and vertebrates have become extinct in the United States whilst worldwide, over 700 extinctions of vertebrates, invertebrates, and vascular plants have been recorded since 1600. Figure 3 shows a picture of a Panay Bushy-tailed Cloud Rat, (Rodentia - Muridae: Crateromys heaneyi) this rather cute looking mammal was only discovered in 1996, (and may not be around much longer), it is considered to be extremely endangered. Endemic (unique to and only found in this area) to the Philippines its habitat is the forest canopy where it feeds on leaves.

A "Pot Pourri" of Extinction

• Worldwide, some 492 genetically distinct populations of tree species (including some full species) are endangered.
• In the northwestern United States, 159 genetically distinct populations of ocean-migrating fish are at high or moderate risk of extinction.
• In Indonesia, 1500 local rice varieties have become extinct in the last 15 years.
• A recent survey of sites in Kenya with wild coffee species found that the coffee plants in two of the sites had disappeared, three sites were highly threatened, and six were possibly threatened.
• More than 40 kinds of freshwater fish in North America have become extinct in the past century, according to the (UN-IUCN).
• In Africa a unique ecological community called the fynbos, supports an extraordinary variety of plants, (about 8,500 species). In the past century, 36 species have become extinct and more than 600 others are at risk of extinction.
• In river basins in North America, naturalists once identified nearly 300 native species of freshwater clams and mussels. Of these, 21 have become extinct since the late 1800's, and another 120 are at risk of extinction.
• Although only 5 out of more than 4,000 species of frogs and toads are known to have vanished in the past century ecologists have recorded massive declines in the populations of amphibians worldwide since the 1970's.
• More than 40 other mammal species in Australia have vanished from more than half of their former range or survive only in protected habitats