The most important lesson learned is that a number of ecosystems, including the one that contains Yellowstone, are specially adapted to large and intense wildfires. This was widely thought to be the case well before 1988, and the wildfires of that year drove the conclusion home. While large destructive fires are unacceptable in regions with extensive encroachment by communities, they are mandatory in a region such as the Greater Yellowstone Ecosystem, if it is to be maintained in a natural manner.