ECOLOGICAL

EROSION PROJECT

Human activities influence tropical forests worldwide, altering their form and composition, and in some cases, threatening their very existence. The reach of industrial scale logging, palm and rubber agriculture, and mining now extends to the most isolated areas. These activities and the hunting and poaching that follow threaten to transform the remaining primary tropical forests into a degraded mosaic, emptied of wildlife. The reduction in animal abundance is expected to interrupt plant-animal interactions, such as seed dispersal, seed and seedling predation, and herbivory.  We study how changes in the animal community cascade to affect forest structure, composition and services through the modification or loss of ecological processes. In particular, we assess whether there are tipping points at which the composition or structure of the plant community might shift from one state to another or at which ecosystem services are diminished or lost.

Ecological erosion is the incremental deterioration or alteration of ecological communities and processes.

Seed traps collect fruits and seeds from the forest canopy.

Our research group works on how human disturbance affects animal and tree communities in tropical forests. 

PATHOGENS
TO PACHYDERMS

Depletion of megafauna, animals that weigh a ton or more, is one of the most damaging ecological consequences of human activity on Earth. Of great concern is the African Forest Elephant, whose population declined 62% in the last decade and now inhabits less than a quarter of its previous range. While some may view extinction of one elephant species as an unfortunate but small consequence of human activity, megafauna loss likely affects entire ecosystems with widespread repercussions for the environment and humanity. The impact of fungal pathogens, invertebrates and small mammal seed predators on forest dynamics are well-studied; but, the impact of megafauna loss on closed canopy forest dynamics remains undefined. To close this gap in knowledge the ecosystem must be viewed in totality, as

the depletion of megafauna likely has cascading effects on the remaining fauna and flora. Elephants, as large browsers, break vegetation and kill saplings, opening up the forest understory; but they also consume fruits and disperse seeds, facilitating reproduction of some tree species - the duality of their impact conceivably stabilizes forest dynamics. In the absence of elephants, vegetation turnover is disrupted and smaller mammals, insects, and fungi emerge as stronger forces in tree recruitment with unknown consequences for forest dynamics and the ecosystem services they provide humans.

 

We are starting this NSF-funded project in 2020 in the Ivindo National Park, Gabon. Collectively, the central hypothesis is that megafauna depletion has cascading effects on remaining fauna and flora, destabilizing forest dynamics. Broadly defining the impact of megafauna in general, and the African Forest Elephant specifically, on closed canopy forests is the overarching goal of this project. The research objectives are to: (1) assess the relationship among trees and the organisms with which they interact over plant life stages; (2) quantify the degree to which defaunation alters these plant-animal interactions and tree recruitment; and (3) generate individual based models to simulate population dynamics of elephant-dispersed tree species to compare extinction probability in simulated populations with and without elephants.

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Nicholas School of the Environment

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