Rising summer heatwave exposure of global peak vegetation productivity

Projected increases in both frequency and intensity of heatwaves during the 21st century pose significant risks to terrestrial ecosystems. Yet, the extent to which these heatwaves threaten peak vegetation productivity, a fundamental driver of terrestrial carbon uptake, remains largely unknow. Here, we used sun-induced fluorescence, a proxy of vegetation productivity, to find all peaks in the vegetation growth during 2001 to 2018 and employed daily maximum temperature to detect spatiotemporal contiguous heatwaves. The study revealed vegetation growth peaked in summer across 86.06% of the Northern Hemisphere and 58.25% of the Southern Hemispheare, with 32.25% of global vegetated areas experiencing heatwaves every year. The temporal dynamics analysis showed that the global advance of vegetation growth peak (48.33%) and the increase of heatwave days (42.67%) both presented large spatial heterogeneity. We found that over half of the global vegetated areas (52.16%) experienced at least one peak of vegetation growth exposed to heatwaves, with the total affected area expanding by approximately 72,700 km² per year. The response of peak growth to heatwave depended on the background climate. These findings highlight the intensifying risk of heatwaves to global vegetation productivity, with potentially severe consequences for land carbon uptake and the resilience of ecosystems to climate change.