Along the North Eastern coastal regions of North America the predominant biome before European settlers began colonizing the region in earnest was the oak savan

Along the North Eastern coastal regions of North America the predominant biome before European settlers began colonizing the region in earnest was the oak savanna: an ecological system dependent on fires. After those settlers arrived they took steps to prevent those fires from affecting their towns and inadvertently by clearing land for farming. The result are forests that are choked with under brush, mass migrations of animals, the spread of parasitic insects, etc. Completely changed the character of the region.