The Importance of Species Diversity to the Ecosystem

The Importance of Species Diversity to the Ecosystem

Does the number of species in a community actually matter for how the ecosystem works? Ecologists have not been able to give a clear, final answer to this question. For many decades, the general belief was that communities with more species tend to be more stable than those with fewer species.

But what does "stability" mean for a biological community? A stable community has three key features:

• It should not show too much variation in productivity from year to year.
• It must be either resistant or resilient to occasional disturbances — whether natural or man-made.
• It must also be resistant to invasions by alien species.

We do not yet know exactly how these attributes are linked to species richness. However, David Tilman’s long-term ecosystem experiments using outdoor plots have provided some tentative answers.

Tilman found that plots with more species showed less year-to-year variation in total biomass. He also showed that increased diversity contributed to higher productivity. So, even if we do not fully understand how species richness supports the well-being of an ecosystem, we know enough to realise that rich biodiversity is not only essential for ecosystem health but is imperative for the very survival of the human race on this planet.

At a time when we are losing species at an alarming pace, one might ask: Does it really matter to us if a few species become extinct? Would the Western Ghats ecosystems be less functional if one of its tree frog species is lost forever? How is our quality of life affected if, instead of 20,000, we have only 15,000 species of ants on earth?

There are no direct answers to such naive questions. But we can develop a proper perspective through an analogy used by Stanford ecologist Paul Ehrlich — the rivet popper hypothesis. …