Editing Predation (section)

=== Biodiversity maintained by apex predation ===
{{further|Keystone species}}

Predators may increase the [[biodiversity]] of communities by preventing a single species from becoming dominant. Such predators are known as [[keystone species]] and may have a profound influence on the balance of organisms in a particular [[ecosystem]].<ref name=Bond2012>{{cite book |first=W. J. |last=Bond |chapter=11. Keystone species |editor-last1=Schulze |editor-first1=Ernst-Detlef |editor-last2=Mooney |editor-first2=Harold A. |title=Biodiversity and Ecosystem Function |date=2012 |publisher=Springer |isbn=978-3642580017 |page=237}}</ref> Introduction or removal of this predator, or changes in its population density, can have drastic cascading effects on the equilibrium of many other populations in the ecosystem. For example, grazers of a grassland may prevent a single dominant species from taking over.<ref>{{cite book |author1=Botkin, D. |author2=Keller, E. |date=2003 |title=Environmental Science: Earth as a living planet |publisher=John Wiley & Sons |isbn=978-0-471-38914-9 |page=2}}</ref>

[[File:Fig. 1 -Riparian willow recovery (26485120926) horiz.jpg|thumb|center|upright=2.8<!--double image-->|Riparian willow recovery at Blacktail Creek, [[Yellowstone National Park]], after reintroduction of wolves, the local [[keystone species]] and [[apex predator]].<ref name="Ripple2004"/> Left, in 2002; right, in 2015]]

The elimination of wolves from [[Yellowstone National Park]] had profound impacts on the [[trophic pyramid]]. In that area, wolves are both keystone species and apex predators. Without predation, herbivores began to over-graze many woody browse species, affecting the area's plant populations. In addition, wolves often kept animals from grazing near streams, protecting the [[beaver]]s' food sources. The removal of wolves had a direct effect on the beaver population, as their habitat became territory for grazing. Increased browsing on [[willow]]s and [[conifer]]s along Blacktail Creek due to a lack of predation caused channel incision because the reduced beaver population was no longer able to slow the water down and keep the soil in place. The predators were thus demonstrated to be of vital importance in the ecosystem.<ref name="Ripple2004">{{cite journal |last1=Ripple |first1=William J. |last2=Beschta |first2=Robert L. |title=Wolves and the Ecology of Fear: Can Predation Risk Structure Ecosystems? |journal=BioScience |volume=54 |issue=8 |year=2004 |doi=10.1641/0006-3568(2004)054[0755:WATEOF]2.0.CO;2 | page=755|doi-access=free }}</ref>