salt impairs plant growth and eventually the soil becomes too salty to grow crops. Already
a third of the world's irrigated land is affected by salinization and this is projected to rise to
over half by the end of the decade.
The combined effects of soil erosion, desertification and salting mean that we have to
feed the worlds still-expanding population on a steadily dwindling area of arable land.
Much of the lost land will be in food exporting countries, like the USA and Australia.
Permaculture offers practical solutions to these three problems. Soil erosion can be
changed to soil creation by adopting no-till methods and by growing tree crops or other
perennials on steep slopes. Desertification is being addressed by introducing people in arid
areas to gardening, as a less destructive form of food production than extensive cropping or
grazing. Re-establishing trees in arid areas is also a permaculture speciality and, once they
are established, trees make their own rain.
Trees can also help stop the process of salt buildup by drawing water down through the
soil towards their deep roots, away from the soil surface. But the real cure for the salt prob-
lem is to avoid causing it in the first place. This means choosing crops that suit the area,
instead of trying to make the local climate suit the crops that we would like to grow. For
example, we could accept a low yield of a dry-land variety of sorghum in perpetuity, rather
than a few years of profitable irrigated cotton, leading to a sterile soil.
Permaculture is certainly sustainable. But how can it produce enough to feed us all?
Most of all by gardening rather than farming . A hectare of cultivated land in China
produces nine times as many calories as a hectare in the USA, and the key to the difference
is a matter of scale. Chinese farming is more what we would call gardening, based on very
small plots with a lot of people involved and very little machinery. North American farm-
ing is based on very large farms with a maximum of machinery and chemicals and as few
people as possible on the land.
The American system is very productive of money. (Though this mostly goes to the sup-
pliers of the machinery and chemicals and the food processors rather than to the farmers.)
But the Chinese system produces a lot of food. This is because the amount of human atten-
tion per square metre is far and away the most important factor influencing crop yield.
This is not to say that we need to use the very laborious methods that are often part
of farm life in countries like China. Permaculture design and methods can take much of
the work out of gardening, whether that work was formerly done by fossil fuels or human
sweat. No-till methods, perennial plants, pig and chicken 'tractors' are examples.
Permaculture can also greatly increase yields, by:
. . . an increased emphasis on aquaculture , growing water plants and keeping fish, both
of which outyield land plants and animals.
. . . taking a multiple output , where conventional agriculture takes only one - for ex-
ample, taking the acorn crop from oak trees as well as the timber yield. This involves seeing
pollutants, such as the carbon dioxide and body heat of the chicken, as potential yields. It