Although extinction is a natural process, the
accelerated rates of extinction occurring today are cause for alarm. Some scientists
believe that today’s extinctions can be compared to the mass extinctions of the past:
extinctions in which tens of thousands of species died out following some massive
catastrophe. There have been five major extinctions, all caused by natural events.
The most well known extinction is that which killed the dinosaurs about 65 million years
ago, presumably from the major climate and habitat changes caused by an asteroid impact.
Unlike the past naturally caused extinctions, the main
cause of the present extinctions is habitat destruction resulting from human activities.
A second major cause for the current extinctions is the overharvesting of animals
and plants. The major difference between today’s extinctions and those of the
past is the source: human activity.
Agricultural exploits and the ever-increasing human
population have severely intruded into the habitats of nearly every species on earth.
Humans are taking over and modifying every last natural habitat on earth.
Humans are also actively removing species from their habitats. When the world’s
population was much smaller, hunting for survival generally was not enough to bring a
species to extinction. However, with today’s population size, even if humans
hunted for only survival, the pressures on species would be so great that most species
wouldn't survive. Additionally, humans are not only hunting animals for survival
requirements; we are taking species for economic gain. These two pressures—habitat
destruction and overharvesting—are resulting in one of the greatest mass extinctions
ever.
| Four main points illustrate
the magnitude of the problem and why so much concern has been raised lately. |
|
- Present threats to biodiversity are
unprecedented because never before have so many species been threatened with extinction in
such a short period of time over such a broad range—the entire earth.
- The existing threat to biological
diversity is exacerbated by the rising demands of a rapidly increasing human population.
- Several independent factors—acid
rain, logging, and overhunting— combine additively to make the situation worse.
- What is bad for biodiversity will
eventually be bad for humans since humans are dependent on the same natural environment as
all of the earth’s biodiversity.
|
