47.2B: Agricultural Diversity
- Assess the interactions of biodiversity with agricultural diversity
Since the beginning of human agriculture more than 10,000 years ago, human groups have been breeding and selecting crop varieties. This crop diversity matched the cultural diversity of highly-subdivided populations of humans. For example, potatoes were domesticated beginning around 7,000 years ago in the central Andes of Peru and Bolivia. The potatoes grown in that region belong to seven species, while the number of varieties is probably in the thousands. Each variety has been bred to thrive at particular elevations and soil and climate conditions. The diversity is driven by the demands of the topography, the limited movement of people, and the demands created by crop rotation for different varieties that will do well in different fields and microclimates.
Potatoes are only one example of human-generated diversity. Every plant, animal, and fungus that has been cultivated by humans has been bred from original wild ancestor species into diverse varieties arising from the demands for food value, adaptation to growing conditions, and resistance to pests. The potato demonstrates a well-known example of the risks of low crop diversity. The tragic, Irish potato famine occurred when the single variety grown in Ireland became susceptible to a potato blight, wiping out the crop. The loss of the crop led to famine, death, and mass emigration. Resistance to disease is a chief benefit to maintaining crop biodiversity; lack of diversity in contemporary crop species carries similar risks. Seed companies, which are the source of most crop varieties in developed countries, must continually breed new varieties to keep up with evolving pest organisms. These same seed companies, however, have participated in the decline of the number of varieties available as they focus on selling fewer varieties in more areas of the world.
The ability to create new crop varieties relies on the diversity of varieties available and the accessibility of wild forms related to the crop plant. These wild forms are often the source of new gene variants that can be bred with existing varieties to create varieties with new attributes. Loss of wild species related to a crop will mean the loss of potential in crop improvement. Maintaining the genetic diversity of wild species related to domesticated species ensures our continued food supply.
Since the 1920s, government agriculture departments have maintained seed banks of crop varieties as a way to maintain crop diversity. Sometimes, however, seed banks are lost through accidents; there is no way to replace them. In 2008, the Svalbard Global Seed Vault began storing seeds from around the world as a backup system to the regional seed banks. If a regional seed bank stores varieties in Svalbard, losses can be replaced from those stored here. The seed vault is located deep into the rock of an arctic island. Conditions within the vault are maintained at ideal temperature and humidity for seed survival, but the deep underground location of the vault in the arctic means that failure of the vault’s systems will not compromise the climatic conditions inside the vault.
Key Points
- Agricultural diversity is driven by the demands of the topography, the limited movement of people, and the needs for crop rotation of varieties that do well in different fields.
- Resistance to disease is a chief benefit to maintaining crop biodiversity; lack of diversity in crop species risks an entire crop being wiped out by a disease to which it is susceptible.
- The ability to create new crop varieties relies on the diversity of varieties available and the accessibility of wild forms related to the crop plant that can be bred with existing varieties.
- Seed companies must continually breed new varieties to keep up with evolving pest organisms.
Key Terms
- blight : any of many plant diseases causing damage to, or the death of, leaves, fruit or other parts