Fifty years ago, it looked nearly empty. Today it is full. A few scientists still doubt that global warming has begun but even the doubters don't dispute that it will eventually occur if we continue to load the atmosphere with carbon dioxide. Today the dispute is more about proper responses to global warming than about its eventual occurrence. Depletion of the Earth's ozone shield, discovered in 1985, is further evidence that we have already exceeded the planet's limits.
Land degradation is further evidence of limits reached and exceeded.
Thirty-five percent of the Earth's land has already been irreparably degraded by human activities. In agricultural areas, soil loss exceeds the rate of soil regeneration by at least 10-fold at a time when a billion people are malnourished. As marginal lands are cultivated, soil loss worsens. Extinction of species offers more evidence that limits have been reached. The regenerative and assimilative capacities of the earth are already exceeded.