Answer:
Reducing the hoofed animal population, which benefits the natural surroundings and smaller herbivores.
Explanation:
The biggest doubling time of all the regions/continents in the world has Europe.
Europe is the only continent that has almost 0% population growth (as of 2014), which practically means that with this pace Europe will need an eternity to be able to double its population, so it makes it the continent with the biggest time needed to double it's population.
Either Hawai'i or Oregon, I live in Oregon and the forests seem very tropical, but the most likely answer is Hawai'i.