`star` Criteria for stability for a biological community
`star` The importance of Species Diversity to the Ecosystem
`star` Loss of Biodiversity


● Does the number of species in a `color{violet}("community really matter")` to the functioning of the `color{violet}("ecosystem?")` This is a question for which ecologists have not been able to give a definitive answer.

● For many `color{violet}("decades, ecologists")` believed that `color{violet}("communities")` with more species, generally, tend to be more stable than those with less species.

● There are some criteria that `color{violet}("confer stability")` to a `color{violet}("biological community :")`

`star` A `color{violet}("stable community")` should not show too much `color{violet}("variation in productivity ")` from year to year

`star` It must be either `color{violet}("resistant or resilient")` to `color{violet}("occasional disturbances (natural or man-made)")`

`star` It must also be `color{violet}("resistant to invasions")` by alien species.


● We don’t know how these attributes are linked to species richness in a `color{violet}("community")`, but `color{brown}("David Tilman’s")` long-term ecosystem experiments using outdoor plots provide some tentative answers.

● `color{violet}("Tilman")` found that plots with more species showed less `color{violet}("year-to-year variation")` in `color{violet}("total biomass.")`

● He also showed that in his experiments, `color{violet}("increased diversity contributed")` to higher productivity.

● Although, we may not understand completely how species `color{violet}("richness contributes")` to the well-being of an `color{violet}("ecosystem,")` we know enough to realize that `color{violet}("rich biodiversity")` is not only essential for `color{violet}("ecosystem health")` but imperative for the very survival of the human race on this `color{violet}("planet.")`

● At a time when we are losing species at an alarming pace, one might ask–

`star` Does it `color{violet}("really matter")` to us if a few species become extinct?

`star` Would `color{violet}("Western Ghats ecosystems")` be less functional if one of its tree frog species is lost forever?

`star` How is our quality of `color{violet}("life affected")` if, say, instead of `color{violet}("20,000 ")` we have only `color{violet}("15,000")` species of ants on earth?

● There are no direct answers to such näive questions but we can develop a proper perspective through an analogy the (`color{brown}(" ‘rivet popper hypothesis’")` ) used by Stanford ecologist `color{brown}("Paul Ehrlich.")`

● In an `color{violet}("airplane (ecosystem)")` all parts are joined together using thousands of rivets (species).

● If every passenger travelling in it starts popping a rivet to take home (causing a species to become extinct), it may not affect flight safety (`color{violet}("proper functioning of the ecosystem")`) initially, but as more and more rivets are removed, the plane becomes dangerously weak over a period of time.

● Furthermore, which `color{violet}("rivet is removed")` may also be critical.

● Loss of rivets on the wings (`color{violet}("key species that drive major ecosystem")` functions) is obviously a more
serious threat to flight safety than loss of a few rivets on the seats or windows inside the plane.


● While it is doubtful if any new species are being added (through speciation) into the `color{violet}("earth’s treasury ")`of species, there is no doubt about their `color{violet}("continuing losses.")`

● The `color{violet}("biological wealth")` of our planet has been declining rapidly and the accusing finger is clearly pointing to human activities.

● The colonisation of `color{violet}("tropical Pacific Islands")` by humans is said to have led to the extinction of more than 2,000 species of `color{violet}("native birds.")`

● The `color{brown}("IUCN Red List (2004)")` documents the extinction of 784 species (`color{violet}("including 338 vertebrates, 359 invertebrates and 87 plants")`) in the last 500 years.

● Some examples of recent extinctions include the `color{violet}("dodo")` (Mauritius), `color{violet}("quagga")` (Africa), `color{violet}("thylacine")` (Australia), `color{violet}("Steller’s Sea Cow")` (Russia) and three subspecies (Bali, Javan, Caspian) of tiger.

● The last twenty years alone have witnessed the disappearance of 27 species.

● Careful analysis of records shows that `color{violet}("extinctions across taxa")` are not random; some groups like amphibians appear to be more vulnerable to extinction.

● Adding to the grim scenario of extinctions is the fact that more than 15,500 species world-wide are facing the threat of extinction.

● Presently, `color{violet}("12 per cent")` of all bird species, `color{violet}("23 per cent")` of all mammal species, `color{violet}("32 per cent")` of all amphibian species and `color{violet}("31per cent")` of all `color{violet}("gymnosperm")` species in the world face the threat of extinction.