Since the arrival and rapid expansion of complex multicellular life around 530 million years ago (called the Cambrian explosion), and up until the arrival of people on this planet, around 200,000 years ago, the World had faced five mass extinctions. Each extinction event saw and went on to cause gargantuan changes in the planet’s natural order.

Looking at two important examples, the mass extinction that marked the transition from the Permian to the Triassic period (251 million years ago) saw the death of around 70% of species living on land and 96% of those living in the sea. But most significantly it marked (and probably caused) the end of global dominance on land of mammal-like reptiles and the rise of archosaurs (a group which includes not only modern day birds and crocodilians, but also dinosaurs.

Then the mass extinction between the Cretaceous and Tertiary periods (around 65 million years before present) saw the removal of 75% of all of the Earth’s species including, famously, the dinosaurs, and made way for the rise of birds and mammals. However the astounding fact seems to be that we are, at present, living through another biodiversity crisis, called the Holocene extinction event. The American Museum of Natural History has stated “that some scientists say that within the next thirty years as many as half the species on the Earth will die in one of the fastest mass extinctions in the planet’s 4.5-billion-year history.”

Another biodiversity expert, Dr Peter Raven (of the Missouri Botanical Garden) estimates, on the basis of there being 10million species in the world (admittedly lower than other estimates which are in the region of 40-50 million species), that 15,000 species become extinct every year! Although this may seem high it falls within the range of other scientists who estimate a rate of species loss of between 20,000 and two million for the 20th century alone. To put this in more context, in 2004 the respected scientific journal Nature included a report stating that “on the basis of mid-range climate warming scenarios for 2050, that 15-37% of species in our regions and taxa will be ‘committed to extinction’.”

But should this worry us? If mass extinction events have happened at least five times before the arrival of humanity, although this latest event may indeed be caused by the destructive needs of modern civilization (and this argument isn’t without controversy since relatively recent ice-ages may also have contributed significantly) we can’t argue that mass extinctions are either unnatural or deleterious to the long-term viability to life (of some sort) on Earth. What’s more, as top dog on this rock what do we have to fear from a biological shake out?

Well top-dog status didn’t save the mammal-like reptiles and the dinosaurs, and who said we were top of the heap anyway? Nigel Stork (an entomologist) has said that “to a first approximation, all multicellular species on Earth are insects”. Maybe, in a superheated world, evolutionary advantage will be handed to a new generation of super insects?

So the bottom line is that, if we do accept that we all have a vested interest in ensuring that life on Earth remains viable for bipedal primates (ie us), then protecting biodiversity remains important for a number of reasons. Firstly, in the context of agriculture, the biosphere is a huge repository of biological alternatives, which humanity uses to develop new crops and modify existing ones. As new viral or pestilential threats emerge the solution will often be found by cross breeding existing species of crops with wild variants. Indeed the dangers of overreliance on a single strain of potato contributed to the widespread failure of the Irish potato crop of 1846. With reduced biodiversity we have access to a reduced database of potential ready-made alternatives.

Secondly science and medicine both rely heavily on chemical compounds found in nature for the development of new drugs while industry relies on a range of organic products such as yeasts, dyes, and oils, to name a few so . So a reduction in biodiversity reduces a valuable research resource. Finally, and maybe most importantly, there are the essential contributions that all the plants, animals, fungi and micro-organisms together make towards creating a stable environment, and habitable planet, with breathable air, drinkable water and eatable food. Any large scale change in the diversity of life on earth, must inevitably impact on quality of life of the remaining organisms.

It isn’t inevitable that the Holocene extinction event will make humans go the way of the dinosaurs: there are still too many uncertainties both about historical measures of biodiversity and the causes of the present crisis. However, we can at least acknowledge that a loss of biodiversity will have a tangible impact on humanity, and could harm the viability if Earth for human habitation. This is why we need to be talking, now, about how we can best conserve nature for the future.