I blame life in general if we have to point a finger at anything. Animals also produce large amounts of CO2 *glares at cows*, insects destroy large amounts of green, grassy areas in some hot climates and something as simple as water wears away at land, completely destroying habitats. Blaming man for everything is futile, when there's more evidence of nature in general "destroying" the earth. We'd moan if we were getting cold and approaching an ice age - the world likes to moan.