My students are constantly amazing me.

The extinction rate is so huge now, we're to the stage where we've got to set up recombinant ecologies. There are no longer enough species left, anywhere, to hold the system together.

Too often, the pastoralist blames the weeds and seeks a chemical rather than a management solution; too seldom do we find an approach combining the sensible utilisation of grasshoppers and grubs as a valuable dried-protein supplement for fish or food pellets, and a combination of soil conditioning, slashing, and de-stocking or re-seeding to restore species balance.

There is one, and only one solution, and we have almost no time to try it. We must turn all our resources to repairing the natural world, and train all our young people to help. They want to; we need to give them this last chance to create forests, soils, clean waters, clean energies, secure communities, stable regions, and to know how to do it from hands-on experience.

There are a few societies that show signs of having been very rational about the physics of construction and the physics of real life. Some of the old middle-Eastern societies had downdraft systems over whole cities, and passive, rapid-evaporation ice-making systems. They were rational people using good physical principles to make themselves comfortable without additional sources of energy.

Few people today muck around in earth, and when on international flights, I often find I have the only decently dirty fingernails.

You can hit a nail on the head, or cause a machine to do so, and get a fairly predictable result. Hit a dog on the head, and it will either dodge, bite back, or die, but it will never again react in the same way. We can predict only those things we set up to be predictable, not what we encounter in the real world of living and reactive processes.