Preliminary assessment of burned area products in the detection of small fires: A case study of China

Previous studies have found that global burned area products based on coarse resolution sensors tend to miss small fires (<100 ha), particularly in those regions where burnings tend to be human-controlled.

We aimed to analyse the accuracy of small fire detection of current global burned area products in China. Most regions in China tend to have small fires due to strict forest and grassland fire suppression policies, as well as straw burning ban policies. According to Chinese government statistics from 2010 to 2019, there are more than 2000 forest fires every year, with an average size of 10.9 ha per fire. However, most of the studies on fire regimes and fire impacts in China used global burned area products with relatively coarser spatial resolutions, most likely leading to considerable uncertainty in the results.

Our assessment included burned area products with coarse spatial resolution sensors (MODIS, Sentinel-3) with relatively high temporal resolution (1 day) and those with medium resolution sensors (Landsat, Sentinel-2) with relatively low temporal resolution (> 5 days). A burned area reference dataset from Sentinel-2 (S2) images was built to validate those burned area products in China. The extent to which the difference in the spatial and temporal resolutions affecting the total burned area was measured based on the spatial and temporal intercomparison of burned area products.

Accuracy metrics, including both omission (undetected burned pixels) and commission errors (unburned pixels classified as burned), were used in this study. The preliminary results indicate that the ability of global burned area products to detect small fires needs to be improved. This work imposes the essential requirement of relatively high spatial and temporal resolution burned area products for small fires.