Climate warming and land use change in Heilongjiang Province, Northeast China

This study explores the relationship between climate warming and rice paddy expansion in Heilongjiang Province of China. It is found that paddy fields more than quadrupled from 3479 km2 in 1958 to 14 564 km2 in 1980, and increased further to 21,940 km2 in 2000. The newly gained paddy fields originated chiefly from dry fields (46.35%), swamps (30.22%), and primary forest (nearly 10%) during 1958–1980. During 1980–2000 paddy fields expanded at the expense of dry fields (70.50%), swamp (16.59%), and grassland (10.13%). Analysis of climate data shows a warming of over 2 °C from the 1960s to the 2000s in most places. All 28 meteorological stations except one experienced a warming trend. Spatially, the expansion of paddy fields coincided closely with the spatial distribution of annual temperature. These fields were located mostly between the isolines of 2–3 °C. Sowing area of grain increased at a modest rate during the 1970s and the 1980s when >0 °C area expanded rapidly. However, sowing area of rice rose in the 1990s and 2000s at a rate twice higher than that for sowing area of grain in the preceding decades. Thus, the expansion of paddy fields at the expense of other land covers was made possible owing to climate warming in the preceding decade. On average, it takes about 20 years for agricultural practices to adapt to the warmer climate.

Research highlights
► The 0°C isoline shifted northwards by thousands of km2 during 1990s-2000s.
► The over six-fold increase in paddy fields coincided closely with climate warming.
► This expansion was made possible owing to a 2.11° C rise in annual temperature.
► Agricultural practices adapted to the warmer climate about 20 years later.