PeopleSystems and Sustainability Lions and Tigers and...Ants, and Enzymes, and Bacteria, and....

PeopleSystems and Sustainability: This Week in the Global Environment

Lions and Tigers and…Ants, and Enzymes, and Bacteria, and… . 

Leaf-cutter ants of the genus Atta are among the most fascinating and complex creatures on earth. Actually, Atta themselves are unable to live simply as “creatures”. They require an enormous and enormously complex ecosystem, managed carefully and constantly, to survive and prosper. 

Wood-“eating” insects, of course, lack the enzymatic ability to digest and process lignin and cellulose, putting wood off-limits as a direct food source for various roaches, beetle larvae, termites, and ants. Rather, they have a gut flora of microbes that CAN process wood into digestible and nutritive biochemical subcomponents. 

Atta ants operate differently from “conventional” wood-degrading insects. Rather than relying on their gut flora, attines use external fungi to break down cellulose and lignin in large underground nests. The nests contain extensive chambers that serve, in a quite literal sense, as farms. The ants cut leaves into appropriately-sized pieces, carry them into the farm chambers, add them to the growing fungal/leaf complex, and then work to maintain the farm chambers. Humidity is carefully controlled, wastes are removed, and the nutritive fungal products are harvested to maintain the metabolism of the entire colony. 

Recently (http://www.sciencedaily.com/releases/2013/06/130614125647.htm) researchers at the University of Wisconsin-Madison have developed an understanding of Atta farms that reveals far more exquisite complexity than was previously known. It turns out that the ant-leaf-fungus system is insufficient for long-term sustainability. Previously unsuspected bacteria appear to be necessary for the system to operate in the long haul. 

And operate it does. Atta process enormous amounts of vegetation, and their colonies reach enormous sizes. The biomass and metabolism of Atta colonies can be dominant herbivores in areas where they occur in high density. 

When I was in school, I worked on whole-system agroecosystem study projects at the University of Georgia Institute of Ecology. I am not an agronomist, I’m a systems ecologist and field biologist. The lesson I took from the agroecology studies might have differed somewhat from those the agronomy folks took. I realized that the agroecology minimum-till fields needed the entire ecological complex to be present, accounted for, and operating for the system to operate at its fine-tuned best. This means such seemingly peripheral organisms as birds, small and medium mammals, even herbivorous insects, usually a “problem” in farming, were necessary for the agroecosystem to function. 

The work from UWM, it seems to me, reinforces this and should be taken as a lesson for human agroecosystems of all kinds. Properly functioning microbiota can cycle positively into soil-producing and maintaining arthropods, which help support herbivores, which help assure that the crops grow when, where and how they are needed. This is true if the agroecosystem is maximum-tillage, full irrigation, artificially fertilized, or if it is small-scale, locally fertilized, minimum tillage, low-irrigation, low fertilization. 

The biosphere is not simple. Components of the biosphere—agroecosystems—are not simple. This makes it tough for us to study them effectively. However, it DOES contribute to (my) belief that components of the biosphere are robust. They are not sensitive, likely to collapse, constantly under pressure, always at risk. They have redundancy, resiliency, and, if managed as carefully as those operated by Atta ants, likely to be highly sustainable. 

Or perhaps I’m over-optimistic. But I don’t think so. We live in a robust biosphere. If we handle it effectively, it will last us for a long time. And can not only contribute to our food supply, but our energy as well. The future looks bright to me. Brighter in the context of the underground farmers, the Atta ants.