I'd come into town from the bush - after 28 years of field work in natural systems - and become an academic. So I turned my attention to humans, much as I had to possums in the forests.

Anything that's any good is self-perpetuating.

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.

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.

Life is also busy transporting and overturning the soils of earth, the stones, and the minerals. The miles-long drifts of sea kelp that float along our coasts may carry hundreds of tons of volcanic boulders held in their roots. I have followed these streams of life over 300 km, and seen them strand on granite beaches, throwing their boulders up on a 9,000 year old pile of basalt, all the hundreds of tons of which were carried there by kelp.

Brambles, in particular, protect and nourish young fruit trees, and on farms bramble clumps (blackberry or one of its related cultivars) can be used to exclude deer and cattle from newly set trees. As the trees (apple, quince, plum, citrus, fig) age, and the brambles are shaded out, hoofed animals come to eat fallen fruit, and the mature trees (7 plus years old) are sufficiently hardy to withstand browsing. Our forest ancestors may well have followed some such sequences for orchard evolution, assisted by indigenous birds and mammals.

My students are constantly amazing me.