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Biodiversity & their causes

Biological diversity is being eroded as fast today as at any time since the dinosaurs died out some 65 million years ago. The number of documented species extinctions over the past century is small compared to those predicted for the coming decades. This difference is due, in part, to the acceleration of rates of habitat loss over recent decades but also to the difficulty of documenting extinctions. The vast majority of species has not yet even been described, and many may disappear before they are even known to science. Moreover, species are generally not declared to be extinct until years after they have last been seen— so figures for documented extinctions are highly conservative. Finally, 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—these are the “living dead.”

Habitat loss not only precipitates species extinctions, it also represents a loss of biodiversity in its own right. The dramatic loss of species and ecosystem obscure equally large and important threats to genetic diversity. Loss of genetic diversity could imperil agriculture. How much the genetic base has already eroded is hard to say, but since the 1950s the spread of modern "Green Revolution" varieties of corn, wheat, rice and other crops has rapidly squeezed out native landraces

We aren’t quite sure who is cutting our forests and who is going to flood our land, but we know they live in towns, where rich people are getting richer, and we poor people are losing what little we have.