Increasing corn cultivation exacerbated crop residue burning in Northeast China in 21st century

China's endeavors to mitigate recurrent crop residue burning (CRB) and improve air quality have yielded positive results owing to recent pollution prevention policies. Nonetheless, persistent challenges remain, particularly in the Northeast China (NEC), where low temperature complicates crop residue management. Here, we examined the effects of cropping pattern adjustment on variations of CRB patterns in NEC during 2001–2021, utilizing the Moderate-resolution Imaging Spectroradiometer (MODIS) burned area dataset, the Visible Infrared Imaging Radiometer Suite (VIIRS) active fire dataset, and the high-accuracy crop planting area maps. Our results revealed an overall upward trend of 805.96 km2/yr in NEC CRB from 2001 to 2021. The corn CRB area accounted for more than 50% of the total CRB area in each CRB-intensive year (2013–2021), and the increasing corn CRB generally aligns with the growing corn cultivation fields. A seasonal shift in CRB was found around 2017, with intensive CRB activities transitioning from both autumn and spring to primarily spring, particularly in the Songnen Plain and Sanjiang Plain. The changing trend of PM2.5 concentration aligned spatially with the shift. Moreover, the CRBs in spring of 2020 and 2021 were more severe than the major burning seasons in previous years, likely due to the disruptions during COVID-19 lockdowns. In certain years, the explanatory power of spring CRB on PM2.5 concentration was comparable to that of other natural factors, such as precipitation. This study underscores the critical need for sustained and region-specific strategies to tackle the challenges posed by CRBs.