Ecological extinction
Ecological extinction is "the reduction of a species to such low abundance that, although it is still present in the community, it no longer interacts significantly with other species". Ecological extinction stands out because it is the interaction ecology of a species that is important for conservation work. They state that "unless the species interacts significantly with other species in the community (e.g. it is an important predator, competitor, symbiont, mutualist, or prey) its loss may result in little to no adjustment to the abundance and population structure of other species". This view stems from the neutral model of communities that assumes there is little to no interaction within species unless otherwise proven. Estes, Duggins, and Rathburn (1989) recognize two other distinct types of extinction: Global extinction is defined as "the ubiquitous disappearance of a species". Local extinction is characterized by "the disappearance of a species from part of its natural range". Keystone species Robert Paine (1969) first came up with the concept of a keystone species while studying the effects of the predatory sea star Pisaster ochraceus, on the abundance of the herbivorous gastropod, Tegula funebralis. This study took place in the rocky intertidal habitat off the coast of