Seed dispersal strategies and the threat of defaunation in a Congo forest

Background

Seed dispersal plays a critical role in shaping plant communities and maintaining biodiversity in tropical forests. In the Congo Basin, most tree species depend on animals (zoochory) to disperse their seeds, with large vertebrates such as forest elephants and bonobos serving as key dispersers. However, hunting and poaching threaten these animals, potentially triggering cascading effects on forest structure and plant regeneration. This study investigates the extent of animal-mediated seed dispersal in the LuiKotale forest in the Democratic Republic of the Congo (DRC) and evaluates how hunting pressure on frugivores may influence tree community composition.

Goals and Methods

The study assesses how defaunation affects seed dispersal and forest structure by analyzing plant dispersal strategies in the LuiKotale forest. Over a ten-year period, researchers conduct a plant inventory, identifying 735 species and categorizing their seed dispersal modes. They evaluate tree community structure across 12 one-hectare plots, measuring the proportion of zoochorous species. In addition, they identify frugivorous vertebrates present in the ecosystem and determine which species experience hunting or poaching pressure. The analysis compares hunting pressure on seed dispersers versus seed predators, with special attention to large-bodied frugivores.

Conclusion

The study finds that 85% of the plant species in LuiKotale produce fleshy fruits and depend on animals for seed dispersal. Among tree species, this figure rises to 95% of individual trees in the surveyed plots. This dominance of zoochory highlights the essential role of animal dispersers in maintaining forest dynamics. However, all observed seed-dispersing vertebrates—including bonobos, elephants, and hornbills—face hunting or poaching threats, while seed predators like rodents experience less human pressure. This imbalance indicates that defaunation could disrupt seed dispersal processes, potentially shifting tree community composition toward wind-dispersed and autochorous species and ultimately reducing forest biodiversity and altering its structure over time.