Narrowing the gene pool

Adapted from MacRae et al. (2002).

Domesticated plants and animals are some of the foundational elements of food production. Their genetic evolution, much of it manipulated by humans over a 10,000 year period, has been central to growth in agricultural productivity. Two interconnected trends, however, threaten the genetic resource base.

A central problem of plant and animal breeding the past 30 years is the narrowing of traits of interest. Historically, breeders have been primarily concerned with yield and resistance to disease. That focus, combined with the privatization of breeding work and associated supporting intellectual property protections, has progressively narrowed the number of varieties and breeds considered commercially desirable. Concurrently, the same genetic material has been used in a high percentage of varietal and breed lines as breeders draw on this narrow range of desired traits. With a high number of varieties and breeds having common genetic material, crops and animals are rendered more vulnerable on a grand scale to environmental stresses. The Irish potato blight of the early 1800s and the corn blight affecting the U.S. corn crop in 1970 are frequently identified as consequences of this process. This process also results in effective extinctions of domesticated plants and animals, ones that then can no longer provide new genetic material should it be required in the event of major perturbations.

A more subtle, but equally problematic result is a narrowing of the range of optimal environment conditions for growth. Many plant varieties are now only competitive against pests in highly controlled environments where agri-chemicals are used. These varieties are not necessarily suitable in low-input and environmentally sustainable systems. Similarly, many animal breeds are only productive in highly controlled environments. For example, some breeds of broiler chickens in caged environments grow muscle tissue so quickly relative to their bone structure that they are unable to walk properly outdoors.

Genetic engineering is in many ways the ultimate expression of this desire to manipulate genetic traits and expressions. Proponents of GE claim that the technology is closely related to other forms of breeding. But for agroecologists, the capacity to use recombinant DNA technology to rapidly create transgenic organisms is a startling departure from earlier approaches, and one with potentially enormous ecological implications. A fundamental assumption of this technology is that biological organisms are explained primarily by their genes. The influence of environment on genes receives less attention. In this way, organisms are seen to be somewhat independent of their ecological context, phenomena are examined as more discrete manageable explanations, and small samples can be inductively generalized as representative of universal phenomena. In practical terms, ecologists are worried about:

  • the movement of transgenes to related varieties and wild relatives and the implications for community dynamics
  • increased reliance on herbicides to manage herbicide-resistant crops and related negative impacts on non-target organisms
  • agroecosystem simplification resulting from the loss of weed populations that feed other organisms
  • negative effects of Bacillus thuringiensis (Bt)- crops on non-target organisms, particularly beneficial insects and soil organisms.