Increasing drought pressure under anthropogenic climate change may jeopardize the potential of tropical forests to capture carbon in woody biomass and act as a long-term carbon dioxide sink. To evaluate this risk, we assessed drought impacts in 483 tree-ring chronologies from across the tropics and found an overall modest stem growth decline (2.5% with a 95% confidence interval of 2.2 to 2.7%) during the 10% driest years since 1930. Stem growth declines exceeded 10% in 25% of cases and were larger at hotter and drier sites and for gymnosperms compared with angiosperms. Growth declines generally did not outlast drought years and were partially mitigated by growth stimulation in wet years. Thus, pantropical forest carbon sequestration through stem growth has hitherto shown drought resilience that may, however, diminish under future climate change.

Instrumental observations indicate that Amazon precipitation and streamflow extremes have increased during the last 40 years, possibly due to anthropogenic changes and natural variability. How unprecedented these changes might be is difficult to determine because some paleoclimatic, instrumental, and climate model simulations suggest that Amazonian precipitation and streamflow may be subject to multidecadal variability with return intervals longer than most direct observations. A new 258‐year long tree‐ring chronology of Cedrela odorata has been developed in the eastern Amazon and has been used to reconstruct wet season precipitation totals from 1759–2016. Reconstructed drought extremes are associated with significant sea surface temperature anomalies over the tropical Pacific and Atlantic Oceans. Strong multidecadal variance is identified in the reconstruction that may reflect a component of natural rainfall variability relevant to forest ecosystem dynamics and suggesting that recent hydroclimate changes over the eastern Amazon may not be unprecedented over the past 258 years.

Tree-ring width chronologies of cedro (Cedrela fissilis Vell.) (1875 to 2018), jatobá (Hymenaea courbaril L.) (1840 to 2018) and roxinho Peltogyne paniculata Benth.) (1910 to 2018) were developed by dendrochronological techniques in the southern Amazon Basin. Acceptable statistics for the tree-ring chronologies were obtained, and annual calendar dates were assigned. Due to the lack of long-term chronologies for use in paleoclimate reconstructions in degraded forest areas, dendrochronological dating was validated by ¹⁴C analysis. Tree-rings selected for analysis corresponded to 1957, 1958, 1962, 1963, 1965, 1971, and 1972. Those are critical calendar years in which atmospheric ¹⁴C changes were the highest, and therefore their tree-ring cellulose extracts ¹⁴C signatures when in alignment with existing post-AD 1950 atmospheric ¹⁴C atmospheric curves would indicate annual periodicity. Throughout our correlated calendar years and post-AD 1950 ¹⁴C signatures, we indicate that H. courbaril shows an erratic sequence of wood ages. The other two tree species, C. fissilis and P. paniculata, are annual in nature and can be used successfully as paleoclimate proxies. Moreover, due to the sampling site’s strategic location in relation to the Tropical Low-Pressure Belt over South America, these trees can be used to enhance the limited amount of observational data in Southern Hemisphere atmospheric ¹⁴C calibration curves.