The report, conflicting with U.N. studies that say more cropland will be needed in coming decades to avert hunger and price spikes as the world population rises beyond 7 billion, said humanity had reached what it called "Peak Farmland".
The report, supplied to Reuters by Ausubel, projected that almost 150 million hectares (370 million acres) could be restored to natural conditions such as forest by 2060. That is also equivalent to 1.5 times the area of Egypt or 10 times Iowa.
It said the global arable land and permanent crop areas rose from 1.37 billion hectares (3.38 billion acres) in 1961 to 1.53 billion (3.78 billion acres) in 2009. It projected a fall to 1.38 billion hectares (3.41 billion acres) in 2060.