Farmland is beginning to revert back to tropical forest in many countries. The NYT reports:
new "secondary" forests are emerging in Latin America, Asia and other tropical regions at such a fast pace that the trend has set off a serious debate about whether saving primeval rain forest — an iconic environmental cause — may be less urgent than once thought. By one estimate, for every acre of rain forest cut down each year, more than 50 acres of new forest are growing in the tropics on land that was once farmed, logged or ravaged by natural disaster.This could be a very positive trend.
"There is far more forest here than there was 30 years ago," said Ms. Ortega de Wing, 64, who remembers fields of mango trees and banana plants.
The new forests, the scientists argue, could blunt the effects of rain forest destruction by absorbing carbon dioxide, the leading heat-trapping gas linked to global warming, one crucial role that rain forests play. They could also, to a lesser extent, provide habitat for endangered species.
The idea has stirred outrage among environmentalists who believe that vigorous efforts to protect native rain forest should remain a top priority. But the notion has gained currency in mainstream organizations like the Smithsonian Institution and the United Nations, which in 2005 concluded that new forests were "increasing dramatically" and "undervalued" for their environmental benefits. The United Nations is undertaking the first global catalog of the new forests, which vary greatly in their stage of growth.
The United States had a very similar experience. Throughout the 18th and 19th centuries, net forestland declined dramatically, but began to grow back in the earth 20th century. The United States has experienced net forest growth for most of the past century. Whole regions of the country that were largely denuded, including much of the northeastern United States. Areas in the east that are designated "wilderness" actually consist of second-growth forest on lands that had been cleared for farming. The shift of agriculture to the midwest combined with increases in agricultural productivity, along with other factors, including the displacement of draught animals with motorized vehicles and farm equipment, combined to facilitate dramatic forest regeneration with dramatic ecological benefits.