I just finished reading Gaia's Garden, a great book by Toby Hemenway on home-scale permaculture that I've discussed before. Along with Omnivore's Dilemma, In Defense of Food, and Fast Food Nation, it has changed the way I view the world, and more specifically, North American gardening and agricultural practices.
As such, I've been more attuned to the plants around me lately and the interactions of each organism with those around it. When Sarah was playing with the boys the other day, she drew Sacha's attention to the army of ants covering Memere's peonies. Sacha of course asked why. Sarah told Sacha and his friend Jacob that the ants help the peonies bloom, so him and his buddy proceeded to try and pick up ants and place them on the peony to help it. When Sarah told me this story, I was caught completely unaware. I was not aware of this interaction.
So I Googled it and what did I find: myriad requests from individuals who wanted to find out the best way to kill the ants on their peonies. Of course. If they're all over the peonies everywhere you go, they must be pests, right? No, they're not.
Ants and peonies share a beneficial relationship. Ants are uniquely attracted to the peony nectar in the unbloomed buds. By going for the nectar and removing it, the ants help the peony buds to open and bloom fully. As well, by taking over the plant, they protect it from other insects that might otherwise harm it. Once the peony is fully bloomed and the nectar is gone, the ants part.
Why would you want to kill them? They actually make the plant more beautiful. How can we think we can intervene in something that's developed over millions of years of evolution? If we were to think intelligently about it, instead of trying to kill them, we'd do what we could to encourage this interaction and let it be. Nature will be nature, and by trying to intervene too often, we're just fighting a losing battle. Why not learn from it and utilize its patterns and interactions to our benefit?
Take a simple example like the Three Sisters Triad of corn, squash, and beans. From Gaia's Garden comes the following explanation: "The cornstalks form a trellis for the bean vines to climb. The beans, in turn, draw nitrogen from the air, and via symbiotic bacteria convert the nitrogen to plant-available form. These nitrogen-fixing bacteria...are fed by special sugars that ooze from the corn roots. The rambling squash...forms a living parasol that densely covers the ground, inhibiting weeds and keeping the soil moist...[Y]ields of this [grouping], measured in calories, are about 20 percent higher than corn grown alone in an equal-sized plot."
What are the consequences of the antithesis to this approach in modern agriculture? Fifty years ago, loss of crops to insects and disease was around 7%. At the time of writing of Gaia's Garden (2000), that figure stood at 14%. If we've become so much more productive in our agricultural pursuits, how could this have happened? To finalize my discussion of natural interactions I will summarize the authors discuss of the causes of this drastic increase.
First off, soil fertility has declined as we use synthetic fertilizers now and have almost completely eliminated crop rotation, a practice that significantly boosts soil health. The other two reasons are much more fascinating though.
1. Clean Cultivation
As mentioned in the book, hedgerows and natural vegetation along backs of fields were common up until very recently. These oases of nature harbored numerous insects and birds that stood in waiting for any pest silly enough to invade the adjoining field. When they did, the insects and birds had lunch. Along came modern agriculture and the desire to make fields as large as possible and remove any possible source of weed seed. Goodbye natural control.
2. Widespread, ill-timed pesticide use
Insects that munch on plants, like aphids, reproduce rapidly. Their predators, ladybugs, being higher up the food chain, reproduce more slowly. Think of a mouse versus a hawk. So let's say you have an aphid infestation in your field. Now that the hedgerow is gone, you already have a decimated ladybug population. But they kick into gear nonetheless and start reproducing as fast as possible. While mommy and daddy munch on aphids, the little ladybug larvae develop. Just about the time when junior is joining the army, Mr. Farmer comes along and torches the field with pesticide, pushing the ladybugs and the aphids to near extinction. The aphids bounce back quickly as their food source remains plentiful, but the ladybugs need time as they need the aphid population to rebound before they can even think about breeding again. Finally, when the aphid population has reached critical mass and the ladies are ready to start growing another army, Mr. Farmer sees the aphids again and thinks, "Damn, my first bout of spray didn't do the job." Kablamo! He drops another spray bomb. After a few repeats of this vicious cycle all the ladybugs are gone and the farmer is in a perpetual battle with aphids.
All I'm saying, in my typical roundabout way, is that after reading this book, I can't look at a typical North American yard without shaking my head. I plan on designing mine based on permaculture principles over the next few years and hope to document the progress. In the meantime, for the sake of nature, if the ants aren't in your house, just leave them be. Maybe you could plant a few peonies to keep them outside?