Healthy food choices are not just healthy for human beings, they can be one of the top ways to help biodiversity in agricultural landscapes. Both in the shift toward plant-based diets and in the shift away from excessive livestock farming, the impact of healthy food choices on the biological diversity of farmland can be summed up through three distinct measurements:
- the replacement of what would have been there;
- the on-farm benefits and damages; and
- the off-farm repercussions of particular choices.
What is Biodiversity?
The internationally agreed upon biodiversity definition developed as part of the Convention on Biological Diversity (CBD) in 1992 at at the Earth Summit in Rio de Janeiro, Brazil says biodiversity is "the variability among living organisms from all sources and the ecological complexes of which they are a part; this includes diversity within species, between species, and of ecosystems."
This means biodiversity is happening at the level of the gene, the population, the ecosystem, and the landscape, all at once.
One of the first, and most obvious, impacts of agriculture is on the physical structure of the landscape. The dynamic redundancy of a forest or prairie is imposed up by or wholly replaced with the activities of a farm. This could be the presence of livestock, grazing through the landscape, or the turmoil of the plow, tilling the land to a raw and ready state.
The on-farm ecosystem of the tilled field is different from its wild predecessor by an order of magnitude. The seer of the field itself has been entirely reset, as if there had been a fire or other immense trauma. All sustained biodiversity is dependent on the width and complexity of the field's margins, which may include hedgerows or wind breaks, or may be non-existent.
In the early 1970s, the US Department of Agriculture actually called for farmers to 'plow to the edge' in an attempt to maximize per acre yields. This destroyed on-farm biodiversity and sent the crops themselves into a dizzying spiral of need as they attempted to live without the ecosystem services provided by the shelter and stability of field margin ecosystems.
These ecosystem services include habitat for pollinators and beneficial insects, reduced soil and soil moisture loss (windbreaks), and increased water infiltration through the extensive root systems of the perennial field margin plants.
Looking at the damage from the plow, one might assume pastures to be less threatened by agricultural practices.
Low-density grazing operations initially seem the logical lower impact choice of the two, but even grazing is not benign: livestock have preferences and will maintain a radius to a water source, meaning a vast field will be narrowly grazed if there is only limited water available. Livestock will also selectively graze, eating what is most palatable (and very likely the most nutritious) and leaving that will which is distasteful to grow and reproduce.
Even in the best of settings, only intensive management and low density has a chance of halting the slow degradation of the quality of the land. Livestock will continue to eat even when the field needs time to regenerate, and will compact the resulting exposed soil.
Far more common are denser operations, which pit the will of the soil microbes in charge of decomposition against the volume of manure being produced. The soil microbes are soon swamped, and the manure accumulates in vast piles or lagoons, leaching excess nitrogen into the off-farm groundwater supplies. This seeps into the rivers, causing algal-blooms that in turn suck all of the oxygen and the biodiverse life forms from the waterway. It also leaches nitrogen into the air, where the chemical reaction known as a nitrogen cascade results in nitrous oxide (laughing gas) accumulating in the atmosphere.
Further off-farm impacts of agriculture expand exponentially as the intensity of the operation rises. The impacts on confined animal feeding operations (CAFOs) on biodiversity will include, for instance, the 'shadow acres' of fields somewhere else required to raise the grain to feed the livestock, as well as the petroleum and other source materials used to make fertilizers and biocides to deal with the monoculture farming practices used to grow feed grains at agro-industrial farms.
Monocultures are rampant throughout contemporary agri-business models as these vast acreages of a single crop (often a single variety of that crop) are conducive to mechanical harvesting methods. These monocultures are more susceptible to failure, be it through unexpected weather fluctuations or through disease and pest.
Increasingly, the 'health' part of healthy food choices will need to consider the broader health of the community, ecosystem, and landscape. Local food systems such as farmer's markets and community supported agriculture (CSA) ventures, which do not have the pressure to withstand long distance transportation, offer a growing resource for a genetically diverse array of foods.
This newly (re)found abundance begins to return agriculture to the redundant resiliency of a wild ecosystem. As farming practices continue to evolve, methodologies like perennial grain crops, permaculture, polycultures, and alley cropping will further this evolution of agricultural bio-mimicry by returning to agricultural landscapes the dynamic stasis of a wild ecosystem.