Enhanced forest temperature regulation covaries with greater heat resistance of ecosystem photosynthesis.

Global forests strengthened ecosystem-scale surface thermal regulation capacity from 2001–2020, shown by widespread declines in the LST–air temperature slope (-0.0014 ± 0.0003 °C °C⁻¹ yr⁻¹; P < 0.01) and LST–air temperature difference (-0.0268 ± 0.005 °C yr⁻¹; P < 0.01).

• Why it matters: It is unclear how forests’ ability to moderate land surface temperatures has changed worldwide, limiting understanding of ecosystem contributions to climate warming mitigation.
• What they did: Using 20 years of satellite-based LST observations (2001–2020), the study quantified trends in LST–air relationships and tested how thermal regulation capacity varies with tree cover, forest diversity, and photosynthesis-related thermal traits.
• The result: Thermal regulation capacity is linked to increased tree cover and warming trends, is higher in species-rich forests, and covaries with the optimal temperature for forest photosynthesis and with photosynthetic resistance to thermal stress.

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