Gaia's Limits

This illustrated essay concerns sustainability. Its simple thesis is that trees do not grow to the sky. Basic facts are used to figure Earth’s human carrying capacity. Soft food and hard petroleum limits are reached within present lifetimes. Liquifying other fossil fuels and biofuels cannot make up for future petroleum shortfalls given a world population at sustainable food limits, with present GDP levels. The issue is not yet addressed by public policy, although more serious and sooner than climate change.