Low-intensity logging and hunting have long-term effects on seed dispersal but not fecundity in Afrotropical forests

Hunting and logging can alter ecological communities, but their long-term effects are seldom studied in Afrotropical forests. Tropical trees respond to environmental disturbance on timescales that usually surpass the duration of ecological studies and changes in tree fecundity and seed dispersal may persist long after disturbance has ended, potentially altering ecosystem function. Hunting related declines in seed-dispersing animal populations are expected to reduce dispersal of the tree species that rely on them, resulting in fewer successful offspring. At the same time, selective logging may alter competitive interactions among species, releasing remaining trees from light, nutrient, or space limitations. Taken together, hunting and logging may alter the community composition of tropical forests, with implications for carbon storage, biodiversity conservation and ecosystem function.

A blue monkey (Cercopithecus mitis stuhlmanni) engaging in seed dispersal (photo taken in Kakamega, Kenya). Image credit: Marina Cords.

A recent study by Nuñez et al., published in AoBP, evaluates the separate and combined effects of hunting and logging on both fecundity and dispersal of animal and abiotically dispersed trees. The authors collected 3 years of seed rain data from a large-scale observational experiment in previously logged, hunted and protected forests in northern Republic of Congo (Brazzaville). They found that low-intensity logging had a meaningful long-term effect on species-specific seed dispersal distances, though the direction and magnitude varied. Tree fecundity increased with tree diameter but did not differ appreciably across disturbance regimes. The species-specific dispersal responses to logging in this study point towards a long-lasting toll of disturbance on ecological function and highlight the necessity of conserving intact forest. Whilst the effects of disturbance on forest structure and animal communities are easily measured, the effects on ecological processes may be more cryptic, long-lasting and difficult to decipher.

Researcher highlight

Chase Nuñez

Chase Nuñez is a global change ecologist and conservation biologist interested in the ecology, evolution, and conservation of tropical woody plants and their dispersers. Chase graduated summa cum laude from the University of California, Davis before moving to Kakamega, Kenya to work with Dr. Marina Cords on her long-term research projects in the easternmost fragment of the Guineo-Congolian rainforest. He then returned to the United States in 2014 to complete a PhD with Professor Jim Clark and Assistant Professor John Poulsen at Duke University researching how understudied Afrotropical forest communities respond to anthropogenic and climatic disturbances. He is now a postdoctoral researcher at the German Centre for Integrative Biodiversity Research (iDiv), Halle-Jena-Leipzig.

Further reading

Nuñez, C. L., Clark, J. S., Clark, C. J., & Poulsen, J. R. (2018). Low-intensity logging and hunting have long-term effects on seed dispersal but not fecundity in Afrotropical forests. AoB PLANTS, 11(1). https://doi.org/10.1093/aobpla/ply074