You could, like a buddy of mine, state that humans are natural too.
But, we only have one planet and a finite amount of resources, so for our own species survival we should be responsible and make every reasonable and effective attempt at sustainable.
India and China are the major polluters of this time, as the US and Europe were during our industrial revolutions. But each individual human owes it to themselves to do their part. If every person took individual responsibility, this would be a better place to live.