Human activity on Earth has always altered the land. When populations were small enough, and productive and accessible land was abundant, people could abandon land that had been damaged by overuse and move on. While some countries still have excess land available, if population growth continues at the expected rate, virtually all arable (fit for cultivation) land will be in use.

The Economic Value of the World's Ecosystems—How Much Is Nature Worth?

Nature performs valuable, practical, measurable functions, without which the human economy could not exist. Many experts contend that, as human activity gradually consumes or destroys this natural capital, the monetary value of the ecosystem to the economy must be calculated and considered. Thirteen economists, ecologists, and geographers studied 16 different biomes (ecological areas such as lakes, urban areas, and grasslands) to estimate the economic value of...