Toby Hemenway: Wise Words

Toby Hemenway: Permaculture Guru Extraordinaire

Nature uses two principal tools to achieve this protection from catastrophe. The first is diversity in space: in size, shape, physical pattern, and composition. If all the pieces of a system are at the same physical scale—all the same size, or the same genetic makeup, for example—a disturbance occurring at that scale will wipe out the whole system. Diversity in scale brings protection. When a hurricane hits a trailer park, the trailers blow away, but the bacteria, mice, and other elements of very different size escape damage. A plague of cats, on the other hand, strikes at the scale of the mice, leaving the trailers and bacteria unscathed. Mature ecosystems have enough diversity in space that any catastrophe may knock out the pieces living at that particular scale but will almost never destroy the whole landscape.

The second protective tool of mature ecosystems is diversity in time, in rate, frequency, and schedule. Understory shrubs often leaf out earlier in spring than canopy trees, which lets the shrubs grab enough light to build plenty of leaves. Then when the trees grow leaves, the shrubs have the photosynthetic area to gather ample light in the dappled shade. Another classic example of diversity in time is the hatching cycle of locusts. Timed to emerge at intervals of years having prime numbers such as 13 and 17, they frustrate the predators whose more regular breeding period requires their food to arrive more predictably.

 

The basis of all agriculture is soil. Healthy soil positively teems with life, including earthworms, fungi and essential bacteria. Mature topsoil is the product of hundreds, even thousands of years of slow growth, decay and decomposition. Within human timescales, soil is essentially a non-renewable resource.

Once exposed, soils are vulnerable to erosion. Even worse, exposed soils release billions of tons of planet-warming CO2 annually.