The Princeton Guide to Ecology

Empirically and theoretically we know that genetic diversity is essential for rapid evolution. In the face of a rapidly changing world driven by unprecedented human impacts, the ability to evolve rapidly may be one of nature’s most precious commodities. Examples of the economic value of genetic diversity are numerous and compelling, but methods for formal economic valuation of this ecosystem service are not well formulated. Even without good methods for dollarizing genetic diversity as an ecosystem service, there are ways of quantifying its value that help inform sustainable and judicious resource management strategies.

ecosystem services. Goods (food, fuel, building materials) and services (flood control, disease regulation, etc.) that benefit humans and are provided by natural ecosystems

heterozygosity. The proportion of individuals in a population that have two different alleles for a particular gene

microevolution. The occurrence of small-scale changes in allele frequencies in a population over a few generations

resilience. The ability of a system to resist or recover from disturbances and perturbation so that the key components and processes of the system remain the same

The importance of genetic diversity is well known to agronomists, who for nearly a century have spoken of genetic variety as a resource to enhance crop vigor and productivity. Testimony to this value is the fact that half the yield gains in major U.S. cereal crops since the 1930s are attributed to genetic improvements (Rubenstein et al., 2005). We are able to breed and select for crops that meet different environmental challenges only because of the genetic variety in those crops, and the goal of plant breeders is typically to maintain as much genetic diversity as possible in case it is needed at some future date. More generally, a central theorem of evolution is that the rate of evolution is proportional to the amount of genetic variation. The quantitative connection between the rate of evolution and the amount of genetic variation provides the foundation for genetic diversity as perhaps the most fundamental of all supporting ecosystem services. It is clear that if there were zero genetic diversity within each species, even modest environmental change or human disturbance would imperil the species and the ecological services that species provide. In order for humans to get a return from nature (in the form of fisheries, timber, soil fertility, and so on) in a varying environment, species must harbor genetic diversity—how much we cannot say, but some for sure.

A second related appreciation for genetic diversity can be traced to the origins of conservation biology, which sought to identify minimum viable population size on the basis of genetic principles, resulting in computer models of extinction probability. The importance of minimum viable population size applies to many of the world’s species, which have only small populations remaining. For example, 17% of the world’s bird species are confined to small populations on islands, and of these, 23% are classified as threatened (Johnson

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