No refuge for Amazon birds

Abstract

Forests that are undisturbed by direct human degradation are often considered to be climatic refugia that can shield organisms from the harshest effects of climate change. However, recent evidence points to population declines of long-lived species in seemingly pristine tropical rainforests. One explanation for this is that species that are adapted to stable microclimates in tropical forests have evolved longer lifespans at the cost of reproductive output, such that their population dynamics may be sensitive to even small changes in the environment. Writing in Science Advances, Wolfe et al. test this hypothesis by analysing a 27-year capture–mark–recapture dataset of 29 Amazonian bird species across 20 undisturbed forest sites in Brazil. Their results indicated that, during this period, the average temperature of the dry season increased by 1 °C and average rainfall during the dry season decreased by 10 mm. This was accompanied by a significant decline in annual apparent survival (alive and captured in the same study area) in 20 of the bird species, and the adverse effects of higher temperature were stronger in longer-lived species than in shorter-lived ones. Temporary increases in dry-season rainfall were also associated with significant improvements in the annual apparent survival of 21 bird species, and the positive trend again was stronger in longer-lived species. The findings indicate that bird communities in the Amazon may be ill-equipped to adapt to rapidly changing environments.

Original reference: Sci. Adv. 11, eadq8086 (2025)