Resilience of lowland Atlantic forests in a highly fragmented landscape: Insights on the temporal scale of landscape restoration

The Atlantic forest is one of the most threatened tropical forest ecosystem in the world, and despite current knowledge, its ability to recover structure and diversity after a disturbance is still a matter of debate. Quantifying carbon stocks and species diversity in forests at different successional stages and assessing their recovery capacity is important for designing local conservation and restoration strategies. We investigated the resilience potential of lowland Atlantic forests at landscape-scale using a chronosequence approach in 160 0.1-ha permanent plots, three old-growth and 13 second-growth forests at various stages of recovery. We assessed whether tree species richness, including species with high conservation values (endemic and threatened), composition and aboveground carbon stock recover along succession; and estimated how much of the old-growth forest values the 20-yr-old secondary forests had attained and the time needed to reach old-growth forests levels. Species richness, composition and carbon stock tended to recover along the chronosequence, while endemic and threatened species showed no relationship with forest age. After 20 yr of succession, the secondary forests recovered on average 52% of total species richness, 21% of species composition and only 16% of carbon stock of old-growth forests. We predicted that the absolute recovery of lowland Atlantic forests would take eight decades to thousands of years, much longer than the 10–40 years targeted by national efforts to restore degraded ecosystems. Despite slow recovery, these regenerating forests are important for climate mitigation and biodiversity conservation as they potentially sequester 1.78 Mg C ha⁻¹ yr⁻¹ and harbor a number of species comparable to old-growth forests. Our findings indicate that achieving landscape restoration and conservation goals through passive restoration can be a challenge, highlighting the need to invest in management plans in areas with relatively low resilience and high biodiversity and carbon conservation values.