Most of us can feel quite passionate about the harm that humanity's persecution or recklessness has done to the charismatic otter, red squirrel or golden eagle. But who, beyond a few dozen specialists in museums and university biology departments, really cares about the hundreds of small, utterly obscure plant and animal species in Britain which are declining or are endangered because of our activities? Why should we make sacrifices or spend money on their behalf?
If you believe in a divine Creation, then answers are easy. We have no right to wipe out what God made. If you are an atheist, you can argue that we have a powerful self-interest in slowing the great wave of man- made extinctions now gathering pace all over the world. You would say that we have discovered thousands of useful products such as drugs and food additives in wild species, and, of course, all our farm animals and crops come from the wild. We continue to find new uses for species or chemicals within them - why damn this stream by wiping them out?
But for me, all the best arguments are moral and aesthetic ones. Many greens talk about the billions of species on earth living in harmony in the great web of life, and the planetary dangers of upsetting a fragile balance. This is actually unscientific bunkum; the Lion King view of nature. A genuine ecologist will tell you that ecosystems are in constant flux rather than balance. While species can have extraordinarily complex and co-operative relationships, for the most part their interactions are utterly ruthless and consist of eating or being eaten.
Nature seems very careless with its own. For the billions of years during which life on earth has existed, individual species have been continuously disappearing. Existing species or entirely new ones soon take their place. But there is enormous creativity and complexity emerging from the ceaseless struggle - you only have to find out a little about a coral reef, a mangrove swamp or an ancient European woodland to understand this. Environmentalists say the destruction of any species by mankind is equivalent to burning a precious, ancient book in a vast library. Wiping out an ecosystem is akin to demolishing a medieval cathedral.
These are powerful images, but I cannot see any connection. Wild habitats and the mind-boggling diversity of species in the sea, on the land and in the air (there are tens of thousands in Britain alone) were created by blind, utterly impersonal forces such as changes in climate, earlier mass extinctions and evolution.
Even so, the most rudimentary understanding of the processes involved leads you straight to the realisation that each species is special, however boring, ugly and even unpleasant it may appear to us. It has its own uniqueness, its own place, its own history, which is of a different order to the boring, trivial uniqueness of each separate grain of sand on a beach. Once you accept that, the fluffy animal approach to wildlife conservation seems barbaric, irrational. Why should red squirrels and golden eagles and beautiful butterflies get all the attention merely because a majority of humans think they are cute?
If we are rational and care to understand the natural world we uneasily live in, then every wild being threatened by mankind's economic and population growth deserves equal conservation efforts from us - including the lowly nail fungus.
There are exceptions - species such as smallpox and the tetse fly which cause serious suffering and death to people. We have the right to eliminate those entirely, provided that in doing so we do not endanger entire ecosystems and ourselves (which is what happened with DDT).
If every species is unique and of equal value, what gives us that right? Two reasons. Homo sapiens is by far the most interesting and important species on the planet - like it or not we are lords of nature. And in choosing to wage war on our natural enemies, we are only playing by nature's own rules.