From site: As climate negotiators heading for the Copenhagen meeting seek a new agreement to stem global warming, the journal Nature has published a study describing eight more fundamental limits on a healthy planet.
Exceeding any of the “planetary boundaries” could overwhelm essential physical, chemical and biological systems: Using too much fresh water, converting too much land to farms, highways or cities, or spewing too much air pollution could block Earth from supporting the approximately 10 billion inhabitants it’s expected to have in 40 years.