Other scientists have demonstrated that the diversity of microbial life greatly exceeds what was even suspected only a decade ago, and even extends thousands of feet into the crust of the earth. The origin of the major architectures of animals, from sea anemones to fish, the major groups of plants, of dinosaurs and modern mammals all occurred in brief bursts. Curiously, many of these creative bursts of evolution follow mass extinctions and other biotic crises, suggesting a link between environmental disturbances and innovation. Ecosystems are adapted to disturbances ranging from fire to severe storms and outbreaks of disease. Such minor disturbances generally increase the number of species in an area, and are even required in many habitats.
Recovery is generally rapid.
More severe biotic disturbances can destroy entire ecosystems, with the rate of recovery dependent upon the immigration of species into the affected area, and how quickly the ecological fabric can be rewoven. Modern ecology provides an explanation for disturbances at this level, but ongoing, human-induced disturbance are on a far greater scale, more similar to biotic crises and great mass extinctions documented by the fossil record. Rebuilding ecosystems after crises of such magnitude involves both the origination of new species and the creation of new ecological relationships, and often produces significant evolutionary innovation. This creative, self-reinforcing aspect of evolutionary recoveries provides much of the impetus for evolutionary radiations, and links them to other episodes of biological innovation. These concerns have driven the proposal for a new program at the Santa Fe Institute on Biological Recovery and Innovation, as a component of the emerging program on Evolutionary Dynamics.