Critical slowing down of semiarid vegetation resilience is amplified by intensifying heatwaves

Critical slowing down is commonly used as an early-warning signature of declining ecosystem resilience. While widespread greening has been documented, vegetation resilience in semiarid regions has received limited attention, and how climate extremes influence this association remains poorly understood. Here, we quantify vegetation resilience by estimating lag-1 temporal autocorrelation derived from complementary satellite vegetation metrics across global semiarid regions. We find that 56.6% of semiarid vegetated area shows increasing lag-1 temporal autocorrelation, and the spatial mean lag-1 temporal autocorrelation exhibits a sustained upward trend during 2001-2024, indicating declining resilience. Using a quadrant framework, 47.5% of vegetated area is classified as greening concurrent with declining resilience, exceeding the 33.8% showing greening with increasing resilience. Moreover, heatwaves intensified, and precipitation declined, with trend magnitudes and land-cover composition varying among greening-resilience quadrants. Spatial error models indicate that increases in maximum heatwave intensity are more strongly associated with declining resilience under drying trends, whereas this association weakens under wetting. Within-quadrant analyses further characterize conditional associations, consistent with greening-resilience decoupling under hot-dry intensification. Our findings suggest that greening can mask declining resilience, underscoring the need to integrate resilience diagnostics into routine greenness monitoring as climate extremes intensify.