Gary Opit, Brunswick Heads
Warren Kennedy is perfectly correct when he writes that large numbers of species have gone extinct since life began on this planet and that we should always try to minimise our effect on other species.
Scientists have estimated that up to 10 species every year naturally go extinct every year. Almost all of them are tiny invertebrates, and that most species survive for millions of years. Animals and plants large enough to see generally do not go extinct unless struck by major catastrophic events, both planet-wide and regional.
Periods of time when there were relatively few major extinctions were 75 million years, 113 million years, 37 million years, 148 million years and 66 million years in that order.
It was after these events that evolution speeded up, as surviving species evolved to fill the gaps in the planet’s ecological systems and scientists estimate that it took between 15 to 30 million years each time before the health of the Earth’s atmospheric, oceanic and terrestrial organs had stabilised.
Regional events have caused some extinctions as sea levels rose or fell, slowly decreasing habitat or allowing immigrants to invade new territories often outcompeting the original residents.
Scientists estimate that humanity is now exterminating 1000 species a year and many of these are key species, essential for the maintenance of the planet’s life support systems.
Species most at risk are often the most successful and populous as they depend on the stability and health of the ecosystems in which they are embedded. Which is why I believe that humanity is highly endangered, being a species dependent on enormous food and energy resources from a collapsing biosphere caused by biodiversity extinctions.