The Amazon has been experiencing an increased recurrence of hot, intense, and prolonged droughts since the 1980s, with the most recent events occurring in 2023 and 2024, marking the first time consecutive extreme droughts were recorded in back-to-back years. As global temperatures continue to rise, the frequency and intensity of these "hot droughts" are expected to increase, amplifying the impact and presenting unprecedented challenges for Amazonian ecosystems. The convergence of higher temperatures and water scarcity generates complex, cascading effects that influence plant stress, tree mortality rates, fire regimes, and carbon and water fluxes to the atmosphere.

Among these interactive effects are essential links between soil moisture and transpiration rates, where declining soil water reduces the ability of plants to transport moisture, with limiting effects on photosynthesis. In response to water deficits, plants regulate their stomatal openings, decreasing CO2 assimilation and reducing productivity. While this offers short-term protection, it diminishes carbon uptake, heightens long-term stress, and increases the likelihood of tree mortality. Conversely, trees that fail to regulate water loss face a higher risk of mortality due to embolisms (blockages in the water transport system) that can cause irreversible damage, creating a critical tradeoff between conserving water and maintaining carbon assimilation. In forests bordering agricultural landscapes, dry edge conditions further intensify vulnerability by fostering fuel-rich environments that drive more extensive and severe wildfires. As drought- stressed and dying trees shed branches and leaves, they contribute to the buildup of deadwood and surface litter, increasing fire intensity and expanding burn areas, ultimately amplifying carbon emissions and ecosystem degradation.

This session will convene experts from diverse fields, including plant ecophysiology, forest ecology, conservation and policy, and Earth system modeling, to examine these multifaceted interactions. By integrating perspectives across scales, ranging from individual plant responses to landscape management practices and forest-atmospheric interactions, this session will foster a deeper understanding of the processes driving forest resilience and vulnerability under climate stress, and provide perspectives of priority areas for conservation and risk mitigation policies. The session’s interdisciplinary focus will attract a wide range of ATBC participants, reflecting the broad relevance and urgency of addressing Amazonian drought impacts.