With good reason, the United Nations has declared 2010 the International Year of Biodiversity, but global attention has been inadequate.
A widely used technical definition of biodiversity is: "The variability among living organisms from all sources, including, inter alia, terrestrial, marine, and other aquatic ecosystems, and the ecological complexes of which they are a part of: This includes diversity within species, between species and of ecosystems." Simply put, it's the incredible number and diversity of life forms on earth, and their complex, mostly unknowable linkages.
Estimates of the number of species currently on the planet vary from five million to 100 million, with a loose consensus around the 10-20 million levels. This is the simplest measure of biodiversity.
What does biodiversity do for us? There are some simple, direct benefits that all of us can see everyday. A number of "economic goods" come from it: medicines, fibers, rubber, wood, paper, oil and so on. But this is just the most mundane and superficial impact of biodiversity. Some of the deeper, complex phenomena, on which humanity depends, are our entire food chain, practically all our "ecosystem services" (for example, the chemistry of the atmosphere, purification of water in nature and its supply, soil nutrient cycles) and climate change, which both affects and is affected by biodiversity.
We, Homo sapiens, are an inextricable part of this complex web of life. It's both presumptuous and silly to ask what biodiversity does for us - a little like asking what the rest of the body and organs do for the bones, or what the rest of the organization does for the accountants.
We don't, and never will, actually understand all the intricacies of this complex web. Rigorous scientific research has given us many insights, among the most powerful being that the more biodiverse a system, the more stable it is.
We are losing this biodiversity at a rate that is about a thousand times faster than the "background rate" of the extinction of species. The "background rate" is the natural rate of extinction derived from fossil records of the past 540 million (sic) years. The potentially tragic destinies of the panda, the tiger and the rhino are always in the spotlight. We should be conscious of the fact that this is less than the tip of the iceberg.
The International Union for Conservation of Nature has developed a widely used classification of the causes of biodiversity loss. This is exhaustive and immeasurably useful, but it's not possible to repeat it here. For our purpose, E.O. Wilson's evocative capturing of the essence of the causes in the acronym HIPPO is sufficient. HIPPO stands for Habitat destruction, Invasive species, Pollution, Human overpopulation, and Overharvesting of wild species. All of this is caused by humans. To this list we can add human-induced climate change.
Some estimates project that 30% of all species currently on the planet will be extinct by 2050. These estimates also suggest that if the rates of biodiversity loss continue to be what they are, most species will become extinct in a few hundred years.
Five times in the past 540 million years, the earth has gone through "mass extinction" - the wiping out of millions of species in a short period of time. In each of these episodes, more than 50% of all erstwhile species became extinct. Fossil records are fairly clear about these extinctions. The last and most famous of these, the Cretaceous Tertiary Extinction, which happened around 65 million years ago, wiped out the dinosaurs.
We are actually living through the sixth such mass extinction, and the current rate of species loss is as much or more than that during any of the previous five episodes. Scientists call this phase the "Holocene Extinction".
Is the situation as desperate and dramatic as I am making it out to be? The scientific evidence is fairly clear - it's up to each of us to draw our own conclusions. It would be useful to remember that this is a drama that has in the past always happened over "geological time scales". This time, it seems to be unfolding in a flash - over human generational time scales.
There are some hypotheses, but we are not sure as to what caused the last five extinctions, nor can we be sure what the earth and life on it was like after each such episode. This, the sixth time, we are sure about the cause – us. However, we can only be as unsure about what earth and life will be like afterwards.
There is another reason why I would like to be unsure about the outcome. This time around, the "cause" – humanity, us - can be conscious of its effect. And if we become conscious enough, we will hopefully do things to reverse the trend, making this not the sixth mass extinction, but an extinction blip in the long history and future of this planet. We need to place all our bets on that.