In 1979, in the book The Sinking Ark, the author Norman Myers suggested that human activities were causing about two extinctions a week on the planet.By the early 1990s he had raised the figure to some six hundred per week.That's extinctions of all types― plants, insects, and so on as well as animals.Others have put the figure even higher―to well over a thousand a week.A United Nations report of 1995, on the other hand, put the total number of known extinctions in the last four hundred years at slightly under 500 for animals and slightly over 650 for plantswhile allowing that this was "almost certainly an underestimate," particularly with regard to tropical species.A few interpreters think most extinction figures are grossly inflated.The fact is, we don't know. Don't have any idea.We don't know when we started doing many of the things we've done.We don't know what we are doing right now or how our present actions will affect the future.What we do know is that there is only one planet to do it on, and only one species of being capable of making a considered difference.Edward O. Wilson expressed it with unimprovable brevity in The Diversity of Life: "One planet, one experiment."If this book has a lesson, it is that we are awfully lucky to be here―and by "we" I mean every living thing.
