In 1918, Nikolai Vavilov stressed the importance of biologic centres of origin as reservoirs of genes for use in cultivated strains derived from those regions.
During World War II, ordinary Russians made extraordinary sacrifices to preserve the biodiversity that was stored in the potatoes at the Vavilov Institute.
Every living thing makes compromises in order to survive in its environment, and the same general principle applies also to populations and their survival.
A successful organism is one which probably does best under optimum conditions, but it is able to survive under conditions that are less than optimal.
A successful population is one in which most of individuals are well-suited to their environment, but which has a range of other genes which are less useful.
Under natural selection, only the strains with the long-term advantages of biodiversity will survive, unlike situation where an artificial selection is applied.
This range of other less useful genes means that when conditions change, some individuals in the population will be able to flourish, or at least to survive.
Possessing a range of genes which might just come in handy at some future time, is what scientists mean when they talk about a population's biodiversity.
When a population of animals or plants falls, it is absolutely certain that many of the rarer genes which were found in the population will be lost forever.
In the same way, if a population is divided into small groups, it is likely that none of the groups will have very much biodiversity, leaving it at risk.
When zoos operate captive breeding programs, one of the things they have to be very careful about is to ensure that they retain biodiversity in their stocks.
Most crop plants exist as monocultures; with genetically identical individuals covering very large areas in contact with each other, leaving the crops at risk.
With monocultures, any pest which is able to survive and do well in that crop is able to spread as fast as it can read and breed and move through the fields.
In many cases, a gene that could help resist the pest will have been removed in the careful selective breeding of high-yield strains, losing biodiversity.
In this way, selective breeding trades off the long-term advantages of biodiversity for the short-term advantages of an increased yield from the crop.