Health at A Planetary Scale
The human footprint on the earth has grown explosively over the past century or two. Two hundred years ago, there were about 1 billion of us; today, we number more than 7 billion. We have harnessed vast amounts of energy, cleared countless forests, dammed thousands of rivers, reconfigured entire coastlines and built vast cities. We appropriate about half the planet’s accessible fresh water and nearly half the desert-free land surface to feed ourselves.
The results are evident at a planetary scale. The globe is warming. Oceans are becoming more acidic. Natural cycles of nitrogen and phosphorus have been greatly altered; runoff fertilizer contributes to hundreds of “dead zones” along coasts. (This year’s Gulf of Mexico dead zone is twice the size of the Chesapeake Bay.) Almost a third of tropical forests and a fifth of coral reefs have been lost, species are disappearing at unprecedented rates, major fisheries are depleted, and persistent organic chemicals have infiltrated even remote ecosystems. Human effects on the planet are so profound that earth scientists have named a new geological epoch: the Anthropocene. . .