http://www.juliansimon.com/writings/Ultimate_Resource/TCHAR2...
We ought also consider the species of animals whose numbers are increased when the human population increases - chickens, goats, cattle, minks, dogs, cats, laboratory white mice, and canaries.
Humans also created a similar replacement: http://en.wikipedia.org/wiki/Heck_Cattle#Controversy
Heck cattle are considered by some the most suitable cattle breed for low intensity grazing systems in certain types of nature reserves, due to their ruggedness and lack of need for human care. Heck cattle today are propagated in some places to fulfill the role of extinct megafauna in the ecosystem.
A replacement was also created for the extinct tarpan: http://en.wikipedia.org/wiki/Heck_horse
Source? What is an ecological standpoint?
The reason to care is that we could, very easily, be left with nothing but rats and pigeons if we don't.