Species Extinction_

1. In biology and ecology, extinction is the termination of an organism or of a group of organisms (taxon), normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point.

2. More than 99 percent of all species, amounting to over five billion species, that ever lived on Earth are estimated to be extinct.

3. A dagger symbol (†) placed next to the name of a species or other taxon is often done to indicate its status as extinct.

4. It’s frightening but true: Our planet is now in the midst of its sixth mass extinction of plants and animals — the sixth wave of extinctions in the past half-billion years.

5. We’re currently experiencing the worst spate of species die-offs since the loss of the dinosaurs 65 million years ago.

6. Unlike past mass extinctions, caused by events like asteroid strikes, volcanic eruptions, and natural climate shifts, the current crisis is almost entirely caused by us — humans.

7. In fact, 99 percent of currently threatened species are at risk from human activities, primarily those driving habitat loss, introduction of exotic species, and global warming.

8. Because the rate of change in our biosphere is increasing, and because every species’ extinction potentially leads to the extinction of others bound to that species in a complex ecological web, numbers of extinctions are likely to snowball in the coming decades as ecosystems unravel.

9. Species diversity ensures ecosystem resilience, giving ecological communities the scope they need to withstand stress.

10. In the past 500 years, we know of approximately 1,000 species that have gone extinct, from the woodland bison of West Virginia and Arizona’s Merriam’s elk to the Rocky Mountain grasshopper, passenger pigeon and Puerto Rico’s Culebra parrot — but this doesn’t account for thousands of species that disappeared before scientists had a chance to describe them.

11. What’s clear is that many thousands of species are at risk of disappearing forever in the coming decades.

12. No group of animals has a higher rate of endangerment than amphibians. Frogs, toads, and salamanders are disappearing because of habitat loss, water and air pollution, climate change, ultraviolet light exposure, introduced exotic species, and disease.

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