Agriculture, excessive logging, and fires are major causes of deforestation. Afforestation and the natural expansion of forests help to decrease the rate of deforestation. The rate of deforestation has decreased from 16 million hectares (61,776 square miles) per year during the 1990s to 13 million hectares (50,193 square miles) per year in the decade 2000–2010 (according to preliminary data for the decade). The net change in forest area for 2000–2010 is estimated at –5.2 million hectares (20,007 square miles) per year (an area about the size of Costa Rica), down from –8.3 million hectares (32,046 square miles) per year in the 1990s.