Situation Report – China

BY MINGCHUN SHI, CONG GAO, AND XINYAN HUANG

The forest coverage rate in China stands at 24.02 per cent, having jumped from 8.6 per cent in 1949 (see figure 1, page 25). Wildfire, as a major natural disaster, has been recorded since the beginning of Chinese culture. Today, most wildfires in China are ignited by humans and clustered in the subtropical region, with interannual variation modulated by precipitation changes in the East Asia monsoon system. On the other hand, wildfires in northeast China are mainly dominated by temperature. Thus, we will discuss these two major fire regimes in China.

The boreal forests, mainly distributed in the northeast and northwest corners of China, are the most frequent lightning fire regions with the largest burned areas. Wildfires in boreal forests mostly occur in snowfree seasons, mainly in the late spring to summer. Between 2010 and 2022, a total of 658 lightning fires were recorded, with a burned area of 21,125 km2 in the Greater Khingan Mountain forest of northeast China. Owing to strict regulations on human activities in this region, the anthropogenic wildfire ignitions in northeast China have been minimized, which is different from the anthropogenic-ignition dominated subtropical region. As a result, the proportion of lightning fires among all fire types in northeast China increased to 92.7 per cent between 2010 and 2022 from 38.1 per cent between 1966 and 2009. The lightning fire season has extended, and both the frequency and burned area are rising, which is attributable to a warming-induced increase in evaporation and fuel dryness. Wildfires in the boreal forests have burned humus and litterfall in the surface layer of soil , where the carbon storage is much larger than that of living forests. These boreal wildfires largely contribute to the role shift from carbon sink to carbon source.

Trends and variations of lightning fire frequencies in the boreal forest of northeast China are modulated by fuel aridity associated with local temperature, which has been closely connected with AMO (Atlantic multidecadal oscillation). The trend of wildfire frequency in the boreal forest of northwest China is nonsignificant because the increased precipitation has mitigated the drying trend associated with rapid regional warming. Furthermore, years with high- frequency wildfires have been observed, coinciding with La Niña events. The boreal forests in northwest China have adapted to the frequent surface fire by growing a thicker bark at the tree base (see photo, page 26).

Increased lightning activity is projected with warming. In the northern high latitudes, the warming rate has been much faster than the global average. Warming has elevated the fuel aridity, shortened the snow cover period, and prolonged the fire season. Together with the increased proportion of the long continuing lightning, all these changes will increase wildfire risk in the boreal forests. To predict and prevent lightning fires, studies are urgently needed on the characteristic of igniting lightning and climate conditions susceptible to ignition.

Southwest China is another major fire-prone area. The incidence and intensity of wildfires have escalated in recent years, leading to considerable ecological and economic damage. Wildfires in southwest China mainly occurred in the dry season from winter to early spring. Notably, in March 2019, a wildfire in Xichang, Sichuan province, resulted in the tragic loss of 30 firefighters. The frequent wildfires in the spring of 2019 in southwest China were attributed to the lowest precipitation and warmer weather, that is, 1.6 C warmer than the historical average since 1960. Moreover, another 19 firefighters lost their lives in the same region in March 2020. The Yunnan province in southwest China also suffers from a high incidence of wildfires. The wildfire ignition there is susceptible to both climatic and anthropogenic factors, mainly daily minimum relative humidity and closeness to agricultural activities.

After the 1987 Black Dragon fire in Northeast China (193 deaths), the Chinese government introduced measures to prevent and manage wildfires. New policies have been applied, such as improving early warning systems, conducting prescribed burning (see the Q4, 2022 issue of Wildfire), increasing firefighting resources, and fostering fire prevention and education. Largely attributed to these efforts, the observed annual wildfire frequency has generally decreased after reaching a peak in 2008 (see figure 2, page 26), although the fire risk was projected to increase. More frequent incidences of heatwaves and long-lasting droughts associated with fast warming have altered spatial and seasonal patterns of wildfires. The 2022 record-breaking high temperature and mega-drought along the watershed of the Yangtze River caused unprecedented wildfire outbreaks in August, during which abundant precipitation and high vegetation moisture usually prohibited fire occurrence.

The warming-drying trend and lightning frequency increase are prominent in northeastern China. With a persistent positive Atlantic multidecadal oscillation phase and fuel accumulation due to strict forest conservation policies, lightning fires in the boreal forest of northeastern China will become more frequent if warming continues. Higher fuel aridity will favor violent combustion and hence a larger burned area. However, prompt extinguishment, owing to earlier fire detection and firefighting arrival, complicates the burned area prediction.

Further restricting human ignition will not help to reduce wildfires in northeastern China, but this policy is vital for wildfire prevention in subtropical China, where most wildfires are human-ignited. The probability of extreme climate events has largely increased with warming. Specifically, the combination of a heatwave and monsoon failure could be much more frequent in the wet season, or late monsoon precipitation arrival would prevail in subtropical China. The worsened fire weather favoring fire ignition and spread could let the human ignition restriction in vain. Studies showed that forests in northeastern and central-northern China are projected to suffer an increased wildfire probability, and regions with intense fire occurrence will shift from south to central-north China by 2060.

Chunming Shi is an associate professor at Beijing Normal University, conducting broad studies on forest and wildfire ecology.

Cong Gao is a PhD student at the University of Hong Kong, focusing on wildfire and climate change.

Xinyan Huang is an assistant professor at The Hong Kong Polytechnic University and a board member of IAWF. His research focuses on peatland fire and AIdriven wildfire forecast.