Feb. 2 is World Wetlands Day, a holiday that has promoted global appreciation and protection of wetlands for 41 years. It commemorates an international treaty signed in 1971, the Ramsar Convention, that aims to conserve swamps, marshes and bogs around the world, from Albania to Mexico to Zambia.

Demographers aren't known for their sense of humor, but the ones who work for the United Nations recently announced that the world's human population will hit 7 billion on Halloween this year. Since censuses and other surveys can scarcely justify such a precise calculation, it's tempting to imagine that the UN Population Division, the data shop that pinpointed the Day of 7 Billion, is hinting that we should all be afraid, be very afraid.