Unsustainable hunting of forest elephants, gorillas, forest antelopes, and other seed-dispersers could have long-term impacts on the health and resilience of Congo Basin rainforests, warns a study published today in a special issue of the journal Philosophical Transactions of The Royal Society B.
Conducting a review of more than 160 papers and reports on trends in wildlife populations, hunting, and land use in the Congo Basin, a team of researchers from Oxford University, the University of Queensland, the University of Stirling, and the Wildlife Conservation Society conclude that unless effective management plans are put into place, hunting pressure in the region is likely to increase, with knock-on ecological effects.
The authors warn that “profound ecological changes initiated by hunting … may even exacerbate the predicted effects of climate change for the region.”
While humans have long hunted animals in Africa’s tropical forests, in recent decades the proliferation of logging roads, which provide access to remote forest areas, and the emergence of large urban markets for bushmeat have culminated in a sharp rise in commercial hunting in the region. Exploding demand for ivory is worsening the situation, resulting in depletion of a range of seed-dispersing species and wildlife that plays a key role in forest ecology. For example, the loss of elephants from forests in West Africa has triggered a shift toward smaller, faster-growing trees that are less diverse and store less carbon.
“Animal-dispersed tree species, particularly those with large seeds dispersed by large mammals, therefore contribute a high proportion of the overall carbon-storage capacity of tropical forests,” the authors write. “Carbon storage may therefore erode over time if tree regeneration is hampered by changes in faunal guilds, including extinction of large specialized disperser species or increases in seed-predating species enjoying ecological release from their predators.”
These forests may be less resilient to the effects of climate change, including increases in the incidence of drought and fire.
“Even the slight drying associated with higher temperatures, rainfall changes and increased human incursion predicted for this region may make forests more vulnerable to fire in the future,” the authors write. “Forest resilience has been used to mean the resistance of the vegetation to change; however, ecological function in even a seemingly ‘resilient’ forest may be significantly affected by the relatively small increases in temperature predicted.”
“Severe ecological changes below the forest canopy, driven by hunting, are already occurring,” said co-author Dr. Lauren Coad of the University of Queensland and the University of Oxford in a statement. “The removal of seed-dispersing megafauna such as elephants and apes could reduce the ability of forests to sequester carbon.”
The authors note that while deforestation has declined in the region over the past decade relative to the 1990s, degradation, road-building, and forest conversion is poised to increase with rising investment in oil palm plantations, rubber estates, and sugar cane fields as well as potential expansion of industrial logging and mining operations.
“Logging infrastructure and industrial roads usher in a domino effect of factors known to intensify hunting pressure, such as population growth from an immigrant workforce, increased income and demand for wild meat, increased forest access and increased extraction to international markets for specialist products like ivory,” they write. “Although logging itself can affect animal densities by modifying habitat at landscape and local scales, evidence across the region indicates that secondary impacts of logging activity are currently of far greater ecological importance.”
Given the risk that hunting pressure, and its associated ecological impacts, could increase, the researchers conclude with a call for better planning in the region.
“If future Central African human and wildlife communities are to rely on the range of ecosystem services currently provided by their rainforests—and if the value of these global goods is to be maintained—immediate management of hunting and integration of good hunting practices into large-scale land-use planning must be considered an urgent priority for rainforest preservation and thus an integral and important part of planning for climate change management and mitigation.”
CITATION: Abernethy KA, Coad L, Taylor G, Lee ME, Maisels F. 2013 Extent and ecological consequences of hunting in Central African rainforests in the twenty-first century. Phil Trans R Soc B 368: 20120303. http://dx.doi.org/10.1098/rstb.2012.0303
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