ur generation is inheriting an ominous precedent. We are the first to be born into a world whose natural wealth of species - its 'biodiversity' - is rapidly falling. Much has already vanished: animals and plants are being driven into extinction at 1,000 times the normal rate. Far more is in danger: by some estimates, one quarter of all the animals and plants on the planet will become extinct over the next few decades.

We are on the crest of the sixth great wave of extinctions in the history of our fragile planet. The previous five took place millions of years before humans first evolved, and seem to have been caused by massive natural disruptions of the climate - some, at least, caused by meteorites hitting Earth. This one is unique in that it is being brought about by just one of the world's millions of species - us.

It is happening as we fell forests, destroy wetlands, concrete over open land and overfish and pollute the oceans, among other destructive activities. We do not even know what we are destroying. There are thought to be between 13 and 14 million different species on the planet. But we know of fewer than 2 million of them, and we have studied only a tiny fraction of these for the benefits they can provide in new foods, medicines and materials. We are burning a great library of knowledge without ever having opened the books.

This way disaster lies, for the planet and for ourselves. There is not much we can do about what has happened already; all human ingenuity will fail to recreate a single vanished species. But we can fight to make sure that this wholescale destruction stops. Let's commit ourselves to campaigning to ensure that the next generation - our children - does not inherit an even more diminished planet from us.