Plants go extinct at a rate of two to three species per day. Many more are in danger of extinction, and the rate is likely to go up as human activities take their toll on the plants' natural habitats. Even when a species survives, the loss of even part of its natural habitat means that it has fewer defenses against pests, diseases, and environmental changes (such as in the temperature, or the amount of sunlight or water available) for the future. In the course of evolution, plants, like all living things, draw on their range of genetic resources – on the variety of different individuals in the species with different strengths and weaknesses – in order to meet new challenges in their environments. The less there is of such genetic diversity, the more likely the species is to face endangerment or even extinction.
There are many reasons to protect endangered plants and their habitats. Even for food plants found widely throughout the world, rare strains exist that hold the genetic keys to healthier and more nutritious varieties.