loss of biodiversity

Since the beginning of agriculture farmers have encouraged and developed many different traits in cultivated crops by the selective sowing of seed. Differing conditions between one village farming community and another resulted in the development of locally adapted varieties. Eventually hundreds of thousands of distinct varieties of widely cultivated crops evolved. These varieties are known as landraces.

With the advent of modern plant breeding much of this diversity has been lost. European landraces had disappeared by the early twentieth century and information regarding traditional varieties is very scarce. It is impossible to know exactly how much has gone.

According to FAO estimates 75% of the genetic diversity of crop plants were lost in the last century. A survey by RAFI found that approximately 97% of U.S. Department of Agriculture lists have been lost in the last 80 years.

Filipino farmers once grew thousands of kinds of rice. Today only two varieties account for 98% of the area sown. Mexico has lost an estimated 80% of its varieties of maize.
Of 8000 traditional rice varieties being grown in China in 1949, only 50 remained in 1970.

The main reason for the loss of traditional varieties is their replacement by modern varieties. The expansion of cash crop agriculture and pasture to feed cattle has contributed to the decrease in the amount of land farmed by small farmers who are more likely to rely upon and preserve the landraces.

Modern varieties are superior in yield, but for this they often rely on high ammonts of inputs, fertilisers and irrigation. Pesticides are relied upon because they lack the breadth of resistance to pests and the adaptability of the less uniform landraces. Pests adapt to overcome the resistance of modern varieties often in as little as three yesrs. Breeding programs to re-insert resistance often rely upon landraces.

Breeding from a landrace requires the elimination of unwanted characteristics. Having to go back to wild relatives to find resistance poses an even more difficult task for breeders because eliminating wild characteristics that are undesirable in cultivated crops may require several years breeding.

Examples of major pest epidemics this century, where crops were saved by resistance found in the landraces are: U.S. wheat in 1904 and 1917, Indian rice in 1943, U.S. oats in the 1940’s and 50’s, and U.S. corn and Soviet wheat in the early 70’s.

As well as the loss of varieties there has been erosion of the genetic base of crop varieties to such an extent that almost all the top breeders are using the same genetic material. There has been a progressive downward genetic spiral as breeders re-cycle well performing germplasm; some have called this the funnel effect.

In 1986 a survey of European breeders of barley and the onion family indicated that breeders predominantly use breeders lines and cultivars when breeding for resistance, stress tolerance and yield. Researchers looking at French wheat concluded, “Genetic variability of French wheat cultivars has decreased, the breeders having crossed only a few well-known progenitors,”

Research about how crop breeding is effecting the genetic base of our food crops is seriously lacking. It is clear that there is increasing uniformity and an over reliance on single genes to confer resistance.

In landraces hundreds of genes may be involved in conferring resistance against a pathogen. Plant and pathogen co-evolve in the local environment; resistance is thereby dynamic and not stabilised.

When faced with whole fields of genetically identical hybrids, pests can rapidly mutate to overcome the resistance in as little as three years. The vast areas of uniform crops reliant on single gene resistance are an open invitation to disaster. The introduction of GE varieties exacerbates this problem, as different crop species all rely upon the same genes to confer resistance.

The maximum genetic diversity of all agricultural crops lies within the centres of genetic diversity where crops were first domesticated. In these regions wild relatives of crop species grow amongst farmer’s fields and in the margins of fields and there is a constant recycling of genes. These regions are under threat from the introduction of modern agricultural practices.

Seed Banks

The response of the international community to the loss of biodiversity was the setting up of seed banks (frequently known as gene banks). There are now 1300 banks containing around six million acquisitions, even this amount represents a small fraction of diversity and many important regions have been overlooked by collecting expeditions.

There are serious drawbacks of this approach to conserving biodiversity. Varieties stored in seed banks are adapting to the conditions of storage. Varieties have to be replanted to regenerate viable seed on a regular basis.

Small samples of seed collected and stored from each “growing out” result in a continual depletion of variability and adaptability. The most important wheat collection in Asia, held at the University of Kyoto grows only five plants per variety for regeneration. Stored varieties become very uniform and adapted to the artificial environment of cold storage.

There is a serious lack of knowledge about the material stored in seed banks. Without information about how the farming systems in which these crops were grown and the rotations they formed part of these varieties cannot be of use to future farmers. Many collections particularly in the south and Eastern Europe are chronically underfunded, poorly staffed and suffer power failures.

The protection of plant diversity is essential for food security and ecological well-being. It would be foolish to depend on national or international projects to look after biodiversity. Agenda 21, a global agreement from the 1992 Earth Summit, recommended the establishment of regional biodiversity conservation projects which involve public participation. What is really needed are grassroots networks of seed savers and plant breeders who are interested in biodiversity protection and enhancement working together to create living seed banks.


“Shattering: food, politics and the loss of genetic diversity”
Cary Fowler and Pat Mooney
published by the University of Arizona Press
(available from RAFI, www.rafi.org)

“Saving the Seed: genetic diversity and European Agriculture”
Renee Vellve
published by Earthscan publications 1992

“Centres of Diversity: global heritage of crop varieties threatened by genetic pollution”
a greenpeace report produced by Jan van Aken Sept 1999

“Biodiversity for food and agriculture: Crop Genetic Resources”
Posted 9 February 1998

“Seed varieties disappearing, Farmers find agricultural options limited”
David Briscoe CBC Newsworld online September 19, 1999