Monday, May 12, 2014

A Backyard Plant Species Count

Permaculture biodiversity
How many plant species live in your backyard? How many are native? How many provide food for you or for birds, pollinators, and other non-human persons—or for everyone? I am not a trained scientist, but I sometimes hang out with biologists, and one thing they like to do is count things, especially living things. One reason is to assess the health of a place, on the principle that the more biodiversity, the better. I’m no permaculturalist, either—no official certificate—though I have polyculture beds and am deeply influenced by the design philosophy and methods. The basic idea is to work with natural systems and imitate their function when establishing a food garden. Again, the more biodiversity, the better.

However, it had never occurred to me to do a backyard species count until I read Eric Toensmeier’s Paradise Lot, an ebullient book about urban permaculture so full of enthusiasm that if you are fortunate enough to have a backyard, you will immediately want to try out some of what he’s doing. He writes about biodiversity and the benefits of a garden full of diverse species and mentions at one point that when people have asked how many species he and his gardening partner Jonathan Bates have, he doesn’t know. Then when he does a count, he comes up with something like 185 different species. More or less, in a small backyard roughly analogous to mine in size.

Inspired by this, I went on a field trip out back to do my own species survey. I knew I had “lots of species” (a term of art), and an actual count came up with between 100 and 120. More or less. More if one counts the seeds I’ve just planted, and the prairie plants I know are there, but haven’t quite emerged from their torpor, less if the seeds don’t take, or the prairie plants have indeed been winter killed. Of the total, half are native. The half that aren’t include weeds that I keep at more or less manageable levels but have never quite eliminated. Every plant provides food and/or shelter for someone. Perhaps a quarter provide food for the human residents. When one counts also affects the totals. Spring ephemerals go dormant. There are, at the moment, hundreds of cotyledons that haven’t declared their allegiance in the form of a second set of leaves (though one can make an educated guess in most cases). You always miss something. Besides time, this exercise depends on memory, and like all things botanical, the result is more approximate than definite.

More than 100 separate species, then. Not too bad, considering, for example, the fact that most of the backyards in my neighborhood might have only ten or twenty species, and all non-native, at that. These are, in my opinion, what might be called ecological deserts, analogous to those urban neighborhoods termed food deserts. Many of the species in these yards may be “ornamental,” and the yards themselves neat and green, but they are not biologically beautiful or elegant, since by definition these terms require good ecological functioning and an ability to help support other living species.

The numbers tell other stories, too. In general, I prefer native species. That half the species are non-native is because when I started to add natives, I did so gradually, as I had funds, and will not pull out (that is, kill) a non-native that is good looking, useful, and non-invasive. That half the species are still non-native also reflects that many things I like to eat, such as parsley, basil, chard, radishes, lettuce, and tomatoes came from elsewhere. The numbers change over time: new species volunteer, I add new plants and regretfully (mostly) remove others. I can’t say I was sorry when I finally vanquished the bishop’s goutweed I inherited from the previous owner. This year I removed a sweet autumn clematis that was more than adequately demonstrating its invasive tendencies. Also this year I’m putting in some American currants and more raspberries. Next spring, after I’ve learned more about the subject, I plan to put a dwarf espalier fruit tree on the fence where the clematis was.

What should the balance be among plant species? It’s hard to know. There are six species of berries. Pollinators love the flowers. Two kinds of berries are only for birds and squirrels. We more or less share the other four. I will put in more prairie plants and may put in more native berries or try out some different non-native vegetables and herbs. I cannot imagine ever reducing the number voluntarily. Perhaps there should be some sort of species count competition among backyard gardeners, with an emphasis on native plants and ecological health, and including local and regional championships. Perhaps that would help people take advantage of the wonderful opportunities inherent in their backyards. What I know is, I feel sure I’ll catch up with Eric Toensmeier soon. Maybe. More or less.

Related Posts: