Modern biology offers wondrous insights into the living world, yet most of what we would like to know, including some things that seem very basic, remains unknown and in the end may be unknowable. For example – just to be really basic – how many species are there? About two million different kinds are listed but there could be anywhere between five million and a hundred million or even more. Eight million is a commonly accepted figure, based on a mixture of data and common sense and gut feeling (and in the end, short of revelation, what else is there?). Whatever the true figure, it seems that about half of all present species are in imminent, realistic danger of extinction. The Earth has seen several “mass extinctions” but none as rapid as the one we are in the midst of now. Humanity is the main cause, and of all our enterprises, agriculture is the most potent.

Three kinds of argument tell us that this matters; nothing more so.

The first is moral arguments. The core of morality is compassion (VI.1), and compassion must extend to all living creatures. Casual obliteration is not compassionate.

The second is spiritual (VI.1). At the heart of all religions, though more prominent in some than others, is the concept of one-ness: that all living things (and, some would say, non-living) are manifestations of the one great “source”. Such an idea is not amenable to scientific “proof” but it must be taken seriously. It is an example of metaphysics as a basis for morality.

The third is arguments of enlightened self-interest. Other creatures between them create the biosphere – the whole living world. If the biosphere breaks down – “ecological collapse” – then we die too. If we seek simply to conserve the creatures that we know are to our benefit – wheat and cattle for food, horses for transport and amusement, and so on – then the whole will surely fall apart. We cannot predict which or how many of the many millions of species are needed to keep the world intact, and never will be able to. Some of the things we would need to know to make perfect predictions, are unknowable.

“Ecoservices” and “ecotourism” are examples of self-interest that could be of general benefit: good for us and good for the world. But enlightened self-interest taken alone is not enough. Among other things, it leaves the world a hostage to fortune. Conservation strategy, like everything else, comes to depend on market prices (as seen in Britain’s now-you-see-it-now-you-don’t policy of set-aside). What matters above all is attitude. Attitude must be cultivated – by metaphysicians of all stripes and also by poets and artists (VI.3), whom the hard-heads write off.

Science can and must contribute too. Thus the quasi-scientific term “biosphere”, first coined in the late 19th century, is far preferable to “environment”, which simply means “surroundings” and all too easily reduces the natural world to real estate and stage scenery. “Gaia”, too, is a supremely spiritual concept, though it is firmly rooted in science.

Agriculture perforce is interventionist. It imposes on the biosphere. But it can do so in ways that are constructive, or at least not utterly destructive. If we really give a damn we must ensure that farming is as bio-friendly as possible. Vague sloganizing (“sustainable intensification”) will not do.