The role of climate in shaping vegetation dynamics and carbon dioxide fluxes in global protected forest landscapes

Protected forest areas (PAs) are vital for biodiversity conservation, climate regulation, and carbon sequestration. Yet their ecological resilience faces increasing threats from climate change and human disturbances. Despite international efforts to expand PA coverage, the effectiveness of existing PAs in maintaining ecological functions under climate stress remains uncertain. To address this, we analyzed climate-driven vegetation dynamics, tree cover loss, and carbon dioxide (CO₂) fluxes across eight globally distributed tropical and temperate PAs between 2001 and 2023. Using climate datasets, MODIS-derived Gross Primary Productivity (GPP), vegetation indices (NDVI and EVI), tree cover loss products, and spatial carbon flux estimates, we assessed site-specific ecosystem responses to climate variability and forest degradation. Significant warming trends occurred at four sites (Crater Mountain, Białowieża, Tasmania, and Wolong), but significant precipitation changes were limited, decreasing in Crater Mountain and increasing in Wolong. GPP showed nonlinear temperature responses, peaking at 22-27 °C and declining sharply above 28 °C, signaling emerging productivity thresholds. NDVI exhibited consistent temperature sensitivity (Jaú, R² = 0.32; Tasmania, R² = 0.43) but weak precipitation relationships. Substantial tree cover loss occurred primarily in Tasmania and Yellowstone, coinciding with significant emission increases in Kahuzi-Biega, Crater Mountain, Yellowstone, Wolong, and Jaú (R² = 0.35-0.70; p < 0.05). Critically, despite rising emissions, most PAs remained net carbon sinks, except Gunung Leuser, which became a net carbon source despite minimal forest loss. Our findings indicate a critical decoupling between forest structure and carbon balance, underscoring the urgent need for adaptive strategies to safeguard ecological resilience in protected forests.