We need to save those species that are critical to the current and future survival of communities.
Rarity is the best indicator of vulnerability of extinction.
Rare species include large species and top predators, particularly because of the community role of predators in limiting prey populations. The cascade may reach to the lower levels of the community since critical predators often consume competitive dominants which leads to enhanced community diversity. An example of a rare top-level predator worthy of preservation based on life history is the Grizzly Bear. The uniqueness of a species is another criterion for preservation. An example of a unique organism is the Sequioa Tree.