Conversions between natural wetlands and farmland in China: A multiscale geospatial analysis.

Agricultural activity is widely recognized as a leading driver of natural wetland loss in many parts of the world. However, little is known about the spatiotemporal patterns of conversion between natural wetlands and farmland in China. This information deficiency has limited decision-making for the sustainable management of natural wetland ecosystems. In this study, we explicitly quantified bidirectional natural wetland-farmland conversions during the periods of 1990-2000 and 2000-2010 at multiple spatiotemporal scales. Our results revealed that about 60% (15,765km2) of China's lost natural wetlands were due to agricultural encroachment for grain production, 74.7% (11,778km2) of which occurred from 1990 to 2000. Natural wetland conversion to farmland was highest in Northeast China (13,467km2 or 85.4%), whereas the natural wetlands in Northwest China demand extra attention because of a notable increase of agricultural encroachment. Natural wetlands in the humid zone experienced tremendous agricultural encroachment, leading to a loss of 10,649km2, accounting for 67.5% of the total agriculture-induced natural wetland loss in China. On the other hand, a total of 1369km2 of natural wetlands were restored from farmland, with 66.3% of this restoration occurring between 2000 and 2010, primarily in Northeast China and the humid zone. Although a series of national policies and population pressure resulted in agricultural encroachment into natural wetlands, there are also policies and management measures protecting and restoring natural wetlands in China. The spatial differences in natural wetland-farmland conversions among different geographic regions and climatic zones suggest that China must develop place-based sustainable management policies and plans for natural wetlands. This study provides important scientific information necessary for developing such policies and implementation plans.