Active Restoration Leads to Rapid Recovery of Aboveground Biomass but Limited Recovery of Fish Diversity in Planted Mangrove Forests of the North Brazil Shelf

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Coastal degradation has spurred active restoration of mangrove ecosystems, from local initiatives to global commitments to increase mangrove forest area by 20% over the next decade. Mangrove restoration projects typically have multiple objectives, including carbon storage, coastal resilience, and fisheries recovery. How planting seedlings, the most common form of active restoration, can promote recovery of mangrove ecosystem functions remains an urgent research need. We quantified multiple ecosystem outcomes of Guyana's national mangrove restoration program, approximately a decade after seedling planting, and compared restoration outcomes with conditions in intact and degraded mangrove forests. Multivariate analyses indicate that intact and restored sites' environmental conditions were similar to each other but different from degraded sites. Aboveground biomass in restored sites (103 Mg ha−1) was 13 and 99% greater than intact (89.4 Mg ha−1) and degraded (0.12 Mg ha−1) sites, respectively. Active restoration successfully increased seedling abundance of both planted and unplanted species, with similar abundance between intact and restored sites. In contrast, fish communities in restored sites remained similar to degraded sites. Restored sites were dominated by a single algivorous fish species, with lower species diversity and commercially valuable fisheries than intact sites. Our results demonstrate that active restoration is a viable option to restore mangrove forest tree biomass and tree species composition in this region. However, even under a best-case scenario for mangrove forest restoration, fisheries did not recover during our study's timespan. Long-term monitoring and controlled experiments will be essential to further understand restoration outcomes for multiple ecosystem services in mangrove forests.