<p>Flash droughts, characterized by rapid onset and increasing frequency, pose significant threats to ecosystem stability and function. However, there remains no global consensus regarding forest responses to flash droughts. Here, using a reconstructed global high spatiotemporal resolution Standardized Precipitation-Evapotranspiration Index dataset and an interpretable machine learning framework, we find that global forests have experienced increasingly rapid, intense, and prolonged flash droughts over the past four decades. Managed forests are more prone to browning from flash droughts than intact forests due to their limited capacity to acclimate to rapid drought stress driven by extreme heat. Notably, our meta-analysis confirms that current forest management practices, designed to maximize ecosystem services, exacerbate the vulnerability of managed forests to flash droughts globally. Our findings highlight the escalating risks posed by increasingly frequent and prolonged flash droughts to managed forests, underscoring the urgent need to integrate resistance and resilience to extreme climatic events into forest management strategies.</p>