Climate benefits of Amazon secondary forests—recent advances and research needs

A quarter of the deforested Amazon has regrown as secondary tropical forest and yet the climatic
importance of these complex regenerating landscapes is only beginning to be recognised. Advances
in satellite remote-sensing have transformed our ability to detect and map changes in forest cover,
while detailed ground-based measurements from permanent monitoring plots and
eddy-covariance flux towers are providing new insights into the role of secondary forests in the
climate system. This review summarises how progress in data availability on Amazonian secondary
forests has led to better understanding of their influence on global, regional and local climate
through carbon and non-carbon climate benefits. We discuss the climate implications of secondary
forest disturbance and the progress in representing forest regrowth in climate models. Much
remains to be learned about how secondary forests function and interact with climate, how these
processes change with forest age, and the resilience of secondary forest ecosystems faced with
increasing anthropogenic disturbance. Secondary forests face numerous threats: half of secondary
forests in the Brazilian legal Amazon were 11 years old or younger in 2023. On average, 1%–2% of
Amazon secondary forests burn each year, threatening the permanence of sequestered carbon. The
forests that burn are predominantly young (in 2023, 55% of burned secondary forests were
<6 years old, <4% were over 30 years old). In the context of legally binding international climate
treaties and a rapidly changing political backdrop, we discuss the opportunities and challenges of
encouraging tropical forest restoration to mitigate anthropogenic climate change. Amazon