Environmentalists often use annual statistics to measure changes in the planet's health.
It's a way to judge progress as well as the growing threats to the global environment. Now, as they change calendars to a new year, conservationists, like accountants, are reviewing gains, losses and annual projections. In tropical areas such as Central America, environmental changes occur so rapidly that the annual evaluation leaves conservationists with mixed feelings of hope and desperation. This equals about 100 acres a minute. An estimated 50,000 species of plants and animals, mostly plants and invertebrates and mostly in the tropics, are condemned to extinction every year, an average of about 140 a day.