Over geological time there have been five mass extinctions of life on earth, evidence for which is preserved in the fossil record.
These mass extinctions, such as the end of dinosaurs at the end of the Cretaceous Period, or the very large, marine extinction that occurred at the end of the Permian Period, help identify major boundaries in the geological time scale.
When the fossil record of these events is considered within the context of the associated sedimentary rocks, there is evidence that wide spread changes in environmental conditions at those points in time caused the destruction and/or redistribution of species habitat.
We are presently entering into a period of wide spread environmental change and species habitat destruction on earth, largely through the actions of man.
There are a large number of issues facing our society that need to be addressed if man himself is to ultimately avoid being included in the list of species lost. These issues include but are certainly not limited to: population growth, climate change, widespread pollution, declining soil fertility, availability of arable land and water supplies, the thawing of the arctic permafrost and release of stored CO2 and methane gasses, the increasing acidification of the oceans and declining natural food stocks.
This is the setting for mass extinction NUMBER SIX which could be the ultimate challenge facing our species.