Editing Ecosystem engineer (section)

===Allogenic engineers===

Allogenic engineers modify the [[biophysical environment]] by mechanically changing living or nonliving materials from one form to another. [[Beaver]]s are the original model for ecosystem engineers; in the process of [[clearcutting]] and damming, beavers alter their [[ecosystem]] extensively. The addition of a dam will change both the distribution and the abundance of many organisms in the area.<ref name= Haemig /> [[Caterpillars]] are another example in that by creating shelters from leaves, they are also creating shelters for other organisms which may occupy them either simultaneously or subsequently.<ref>{{cite journal | last1 = Jones | first1 = CG | last2 = Lawton | first2 = JH | last3 = Shachak | first3 = M | year = 1997 | title = Positive and negative effects of organisms as physical ecosystem engineers | journal = Ecology | volume = 78 | issue = 7| pages = 1946–1957 | doi=10.2307/2265935| jstor = 2265935 }}</ref> An additional example may be that of [[woodpecker]]s or other birds who create holes in trees for them to nest in. Once these birds are through with them, the holes are used by other species of birds or mammals for housing.<ref name= Haemig />