Many tree species depend at least partly on animals for seed dispersal. Writing in Proceedings of the National Academy of Sciences USA, Fricke and colleagues show that human-caused disruption of seed dispersal by animals could have potentially large effects on the ability of tropical forests to regrow and accumulate carbon. Combining information from published databases, observations from vegetation plots, and trait-based spatial modelling, the authors link local losses and hindered landscape movement of seed-dispersing birds and mammals to reduced seed dispersal function in the tropics. They report that seed dispersal disruption has increased in the past two decades, especially in regions with higher forest losses and fragmentation. Next, the authors examined the relationship between seed dispersal disruption and carbon accumulation rates in thousands of tropical forest plots to estimate the gap between potential and realized carbon gain due to impaired seed dispersal. According to their analyses, the reductions in carbon gains due to seed dispersal disruption are considerable and exceed those attributable to drought and fire, with potentially up to four times less carbon accumulation in areas with the most severe losses of seed dispersers. As a consequence, models that do not account for impaired seed dispersal are likely to overestimate natural forest regrowth. Although Fricke and colleagues caution that uncertainties from data limitations and biases are inherent to their estimates, the findings suggest that seed-dispersing animals are key to tropical forest regrowth.
Original reference: Proc. Natl Acad. Sci. USA 122, e2500951122 (2025)
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