In the winter, you look for color wherever you can find it.
English ivy is a introduced species much like ourselves. It can take over a plot of ground much like ourselves. It's tenacious. It's relentless. It dominates and eventually crowds out or kills the native plants including the trees. It takes no hostages. How friendly is that?
In the end, you are left with nothing but ivy, so goes the biodiversity, and the parcel that remains is known as an "ivy desert."