De(re)forestation and climate warming in subarctic China

Although tropical deforestation bears a close relationship with climate change, its exact contribution to climate warming and its threshold of exerting a noticeable influence remain unknown. This study attempts to bridge this knowledge gap by analyzing deforestation data of Heilongjiang Province, China in relation to climate data. It is found that forest cover was reduced from 238,335 km2 in 1958 to 216,009 km2 in 1980, and further to 207,629 km2 in 2000. During this period the provincial annual temperature rose by 1.68 °C, against the nation-wide warming of 0.99 °C during the same period. At the provincial level the observed deforestation caused a warming in the vicinity of 0.69 °C. This warming does not bear any definite relationship with latitude and elevation. At the local scale, deforestation is related inversely to the rise in decadal temperature in the form of ΔT = −0.013ΔF + 0.4114 (R2 = 0.30). There is a positive relationship between the accuracy (R2 value) of predicting climate warming from deforestation and its severity. The critical threshold for deforestation to exert a noticeable impact on climate warming (e.g., R2 = 50%) appears to be 5 km2. The amount of forest cover at the beginning of a period can inhibit temperature rise, but its exact effect on climate warming is difficult to quantify.

► Forest cover in Heilongjiang decreased by 30,706 km2 during 1958–2000.
► At the provincial level deforestation caused the climate to warm by about 0.69°C.
► Locally, deforestation is related inversely to climate warming (R2=0.30).
► Accuracy of predicting warming from deforestation is correlated with its severity.
► 5 km2 is a critical deforestation threshold exerting tangible influence on warming.