Unfamiliarity

Earth, as we know it on Earth 1, is relatively the same, yet the humans have lost all possibility of sustaining plant life for extended periods of time. The larger cities needed to be evacuated due to mass anarchy and the cities overpopulation led people to the farmlands being hyper-colonized by the humans. Science has proven a great help as many inventions are being used in order to sustain pollination of mass groups of plants. Over time, without animals, humans have begun routing entire forests to make way for new construction materials. In rough span 50 years, if the humans do not find a solution for their lost animal crisis, there will be no way to sustain plant life in any shape or form.

On the other hand, Earth 2 over time will see a drastic increase in plant life, specifically in the major cities. Animals will now be able to reclaim the land where they see fit. Major cities will be overrun with various tribes, and the animals will begin taking the former homes of the humans as their own. Those that still prefer the outdoors can do so, but many of the predatorial tribes hunt in large packs. Those that survive the Rat Pact, did so by adapting to the enviroment known so well to their human counterparts.