Arable land is an essential resource for the production of food and thus constitutes one of the most fundamental resources for mankind. This resource is burdened by population growth and economic development. The statistic data from the Food and Agriculture Organization of the United Nations showed that the world's arable land area was 1.401 billion hectares in 1990, and dropped to 1.381 billion hectares in 2008; with the continued population growth, the world's per capita arable land was 0.265 ha in 1990, and dropped to 0.205 ha in 2008. By 2050, the world's population will reach 9.1 billion. Assuming that the world's arable land area in 2008 remains unchanged to 2050, the world's per capita arable land would fall to 0.151 hectares. Having enough arable land to feed the world population in 2050 is a major challenge, and it is a meaningful task to explore the arable land dynamics for the major countries of the world.
This paper selected 21 countries for a case study, and the arable land dynamics and their possible driving factors for these countries were discussed. These countries includes ten countries with the largest cultivated areas in the world, and the countries whose population will exceed 1 billion by 2050. The research results show that, from 1961 to 2007, increasingly more countries' arable land areas were declining, and almost all of the countries are facing the shortage challenges of arable land. In fact, 90.5% countries have suffered a downward trend of per capita arable land, which implies that the world food crisis is constantly increasing. Considering the change of total arable land area and per capita arable land area, the 21 countries can be divided into four groups: (1) Total arable land area and per capita arable land area increase at the same time; (2) Total arable land area and per capita arable land area decrease at the same time; (3) Total arable land area increases but per capita arable land area decreases; or (4) Total arable land area decreases but per capita arable land area increases.
Among the different situations, population growth and economic development have been two of the key driving forces for the arable land changes. However, due to different land use potentials and different degrees of political stability, the influence factors of arable land are different among the referenced counties. For Brazil, agricultural acreage expansion and the ethanol production increase are important reasons for deforestation and arable land increases. For Bangladesh, Japan, Russia and the United States, urbanization and industrialization are the main reasons behind the reduction of arable land. However, for the Ukraine, the reduced total arable land and increased per capita arable land are closely connected to the sharp population drop and increased urban development. For the other 15 countries, rapid population growth and urbanization lead to reduced per capita arable land; at the same time, population growth has also become an important driving force for these countries to increase the total amount of cultivated land to ensure food security. However, because different countries have different reserve land resources, the arable land growth rate among these countries is significantly different.