Conservation genetics aims to apply principles of genetics to insure that biodiversity is maintained in an ecosystem. One important factor is that the gene pool is maintained and a variety of genes per trait are maintained. That is healthier for a population, especially if environmental conditions change. More genetic variability means a reduced amount of inbreeding, and greater fitness as per the theory of natural selection. An example of this is when year after year, the same crop species is grown. If a fungus now threatens this species and it has no variability in its gene pool, the crop may be wiped out. This could be solved by interbreeding with a wild strain of this plant that could add other alternative genes that may help resist the infection.Genetic diversity becomes diminished when habitats are destroyed and species are fragmented into smaller groups with a smaller amount of alleles for various traits. With a lower number of genes in the gene pool of a species, the more at risk it becomes for extinction. Zoos and seed banks are ways of preserving the DNA of species that in the wild are at risk of extinction. Captive breeding programs and re-introduction into the wild is another technique to attempt to thwart extinction and preserve genetic diversity.