Sustainability has become a buzzword- it’s used in reference to energy policy, abiotic natural resources, and cultural practices. It’s also being used in reference to agricultural practices. Though we’ve improved on crop yields through modern farming methods, there are still ways in which we can increase our efficiencies while simultaneously providing a place for nature to thrive.
Let’s think in terms of spatial efficiency and functional efficiency for a moment, considering spatial to be the amount of stuff we can pack in a given location and functional being the number of different tasks that can be accomplished per organism. From this standpoint, traditional farming produces food but depletes resources and only yields food in a strictly planar fashion. It certainly has advantages in terms of scale and efficiency of production of the food crops we’re interested in, but at the cost of damaging ecosystems and reducing habitat for other flora and fauna. Not only that- traditional farming methods also tend to increase soil erosion and deplete the nutrients that every living thing in an ecosystem relies on. Done responsibly, using crop rotation and methods such as no-till, it can certainly meet our needs, but it’s still at a cost- a cost to us and to the ecosystem of which it is a (minimally contributing) part. Further, a modern farm requires significant inputs of fertilizer to maintain the soil, fertilizer that often ends up in the streams and rivers of a watershed, promoting algal blooms and adversely affecting oxygen levels, not to mention that a 2006 Cornell University study estimates that the U.S. is losing topsoil at 10 times the natural replenishment rate due to agricultural processing, On the harvesting side, though, it’s hard to argue against the efficiency of food collection in bulk, and demands for food are projected to rise globally during the 21st century.
Polyculture tries to mimic the kind of functioning you see in a natural ecosystem by establishing multiple species in the same area. Plants, like people, have tastes and requirements for certain nutrients as well as differing root depths; a diverse group, by definition, can make better use of the soil conditions in a place than a single species can. By allowing the soil to stand as-is, soil development and commensurate expansion of the flora and fauna that live within it can occur. This change, coupled with the recycling of biomass, allows the system to be far closer to a closed system and dramatically reduces the necessity of chemical inputs. Inclusion of fauna and the diversity of plant species makes such a “farm” far less of a target for pests and improves its ability to weather disease. Greater vegetative cover reduces the rate of evaporation and provides more habitat for fauna. This same difference also allows for greater infiltration of water into the soil and, eventually, into the plants or the water table. Perhaps surprisingly, research indicates that the yield for polycultures is greater than a monoculture of equivalent area and is far more resistant to climate and weather extremes. Far from being an aberration or temporary fad, polyculture has been practiced for the majority of human history with great success. Where the system has issues is from the set-up and harvesting standpoint. While a conventional monoculture can be harvested with minimal human input using automation, harvesting food from a polyculture is significantly more labor intensive. Likewise, planning and planting a polyculture garden represents a significant effort. Such concerns should not be treated lightly, however, that effort can be turned into an opportunity by using it as a chance for a community to gain gardening skills, get physical exercise, and understand the natural world in something more akin to its proper context.
Polyculture isn’t just a terrestrial phenomenon. Many studies have been done investigating the benefits of polyculture principles in the context of aquaculture- one method most fish owners can appreciate and understand is having a scavenger species help to control plankton and algae populations while simultaneously providing a food source for a predator species. Another is to have a plankton and/or herbivorous feeder such as tilapia along with a predator such as bass. Such a combination can actually increase the proportion of prey species, especially when the predator is chosen to reduce the population of small fish in the system. As one might expect, there are examples where this system has been combined with terrestrial polyculture to create an even larger system with enhanced water and waste management characteristics.
Polyculture certainly is not a perfect solution to our food production sustainability issues; much as the Biosphere 2 team learned in the 90’s, it can be extremely challenging to design a working ecosystem with a subset of the full range of organisms found in the natural environment. Further, harvesting the food grown is certainly a more complicated matter than in a monoculture farm. However, if you look at the promise of this farming method from both the technical and community aspects, it would seem to be an excellent start to regaining some of the relevance of the natural world while putting more healthful food on the table.