February 21, 2010

Sustainability just science backing up good sense

By Tom Atwell
Staff Writer

Sustainable gardening is a trend. Many growers, mostly smaller food farmers but also some ornamental garden designers, are working toward sustainability.

An example of entropy in nature happens when a tree falls down. Over time, fungi break down that tree into water and carbon dioxide, which are much simpler than the tree trunk.

So when New England Grows, the trade show for the horticulture industry held each winter in Boston, offered a lecture on ''The Scientific Underpinnings of Sustainability,'' I figured I could come away with some useful knowledge. What I didn't realize was that I was going to have to learn about the laws of thermodynamics, specifically the second law of thermodynamics, or the entropy law.

All I knew about entropy came from Warren Zevon's ''Run Straight Down'' on 1989's ''Transverse City'' album, so this was all new to me.

Tom Wessels, a professor of ecology at Antioch University in New Hampshire, explained that the entropy law in its simplest form is that everything eventually moves from order to chaos, that complicated systems eventually get simpler as their energy and materials diffuse.

But the law of self-organization counters the law of entropy, in that systems can increase their complexity as parts of them become more specialized and tightly integrated.

These laws cover political and economic structures as well as the natural environment, and Wessels spent quite a bit of time on the non-gardening part, but I am going to skip that. I want to know what it all means when the shovel hits the soil.

An example of entropy in nature happens when a tree falls down. Over time, fungi break down that tree into water and carbon dioxide, which are much simpler than the tree trunk.

Another example is erosion, Wessels said. Soil is complex, with animals ranging in size from single cells to earthworms living inside it, as well as vegetable matter. But when the topsoil is washed away, you end up with simpler subsoil that is mostly small pieces of rock.

People can speed up entropy.

''Clearing a rain forest in Argentina to grow soybeans is a form of entropy,'' Wessels said. ''A rain forest is highly complex, and a soybean field is a monoculture.''

Self-organization often involves two species working together -- eventually for the benefit of both.

''When these interactions first occur, it is usually highly negative,'' Wessels said.

The example he used was chestnut blight, which hit America in 1904. The American chestnut was once the most common tree in the forest, containing nuts that were tasty and nutritious even when picked and eaten raw off the tree.

Eventually, almost all of the American chestnuts were killed off by the blight. But not all of them. The blight has to feed on American chestnuts, and if there were none, the blight also would die.

Some American chestnuts have a resistance to the blight and continue to live, including two huge examples that Wessels saw in the Berkshire Mountains in western Massachusetts. So he thinks that in time, enough seeds with resistance will be found and transplanted to allow the tree to come back.

''Eventually it gets to a state of equilibrium,'' he said. ''I think the same thing will happen with the emerald ash borer,'' an exotic insect that was first found in America in Michigan. It is killing almost all the ash trees in its path, and has spread east as far as New York state.

That is one example of self-organization. Here are some others:

In the natural world, species work out arrangements that are beneficial to all. A specific ant lives inside hollow thorns of the bullhead acacia, and in turn protects the acacia from predators. Hawks and owls eat the same rodents, but the hawks hunt in the day and the owls at night. Flowers need to be pollinated, but they aim at different pollinators. Bumblebees, honeybees, hummingbirds and other insects all do best with different-shaped blossoms.

So, sustainability and self-organization are good things in a landscape. How do you get there?

First, Wessels said, since entropy relates to loss of energy, be frugal in your use of energy.

Also, use native plants.

''Native plants have developed in the area and are co-associated with other species in the area and will take up less energy,'' Wessels said.

A landscape with a lot of different plants, including ones that are not native, may look complex but botanically may not be if the plants require the same types of food and environment to thrive.

You should also have a lot of solid objects in your garden.

''If you have increased physical structure and stability, the landscape is more sustainable,'' he said.

Trees and shrubs are more stable, with more structure than herbaceous perennials, so you need some trees and shrubs. Having stone walls and other hardscaping items helps, because it provides a different environment for different types of animals and plants.

Which, to be perfectly honest, we all knew was the best kind of garden anyway. It's just nice that the science backs it up.

Tom Atwell can be contacted at 791-6362 or at:


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