Impact of Declining Animal Populations on Tropical Forests (2021-2022)


Tropical forests are one of Earth’s best defenses against rising CO2 levels. They act as a major carbon sink, absorbing 25-33 percent of atmospheric carbon emissions. Nearly half of aboveground carbon (AGC) is accumulated in the largest trees, giving them outsized importance in climate change mitigation strategies. 

Tropical forests are important for carbon storage, but human activities reduce their size and transform them into a source of emissions. Logging and burning are the most conspicuous disturbances. But cryptic disturbances, like hunting, can also reduce the carbon storage and sink potential of rainforests. 

Large vertebrates have strong top-down control on forests via ecological processes, such as herbivory and seed predation, by which they alter forest structure and composition. For example, chronic thinning of small trees by elephants alleviates competition for resources in the low canopy, allowing slow-growing trees to attain larger sizes – giving rise to higher total AGC stocks. 

Extinction of forest elephants alone is estimated to decrease AGC by seven percent in central African forests. Globally, loss of terrestrial vertebrates, known as defaunation, is occurring at an unprecedented rate. 

Project Description

This project aims to investigate how declining animal populations impact carbon stocks in tropical forests. Team members will quantify the effect of defaunation on forest carbon stocks and ecosystem services in the Ivindo National Park, Gabon. They will measure carbon stocks at ten sites along a known gradient of defaunation. Within each plot, they will tag, identify and measure trees to determine incremental growth. In each plot, the team will collect environmental variables (e.g., canopy openness, aspect, elevation, distance to rivers, presence of elephant trails or human sign) and install camera traps to measure variation in wildlife abundance among sites. 

To determine the effects of defaunation on ecosystem services, the team will conduct a literature review of the traditional uses of tree species in northern Gabon. Based on the review, team members will develop a formal survey for implementation in Gabon. Accompanied by Gabonese collaborators, they will interview men and women in ten villages to refine the list of traditional uses of trees and assess their relative importance to local people. After data collection is complete, they will estimate total aboveground carbon for each plot. 

The team will then examine the relative effects of defaunation and environmental variables on carbon stocks, stand characteristics (species composition, tree height) and ecosystem services. The resulting models will be used to create a carbon map for the national park and surrounding forests. 

Learn more about this project team by viewing the team's video.

Anticipated Outputs

1-2 scientific publications; website; impact reports


Summer 2021 – Summer 2022

  • Summer 2021 (optional): Conduct fieldwork in Gabon; photo-document expedition for project website
  • Fall 2021: Process data; analyze data; build website
  • Spring 2022: Write scientific publication
  • Summer 2022 (optional): Conduct additional fieldwork in Gabon

This Team in the News

Meet the Members of the 2021-2022 Bass Connections Student Advisory Council

Summer Spotlights: How Four Ph.D. Students Advanced Their Research

Summer Research Snapshots 2021


Image: Waterfall in Ivindo National Park, Gabon, by Jefe Le Gran, licensed under CC BY 2.0

Waterfall in Ivindo National Park.

Team Leaders

  • Vincent Maicher, Nicholas School of the Environment-Environmental Sciences and Policy
  • Halina Malinowski, Nicholas School of the Environment–Ph.D. Student
  • Sari Palmroth, Nicholas School of the Environment-Environmental Sciences and Policy
  • John Poulsen, Nicholas School of the Environment-Environmental Sciences and Policy

/graduate Team Members

  • Enikoe Bihari, Master of Environmental Management, Ecosystem Science and Conservation, Forest Resource Management-MF
  • Camille DeSisto, Ecology-PHD
  • Courtney Horn, Master of Environmental Management, Ecosystem Science and Conservation
  • Aubrey Knier, Master of Environmental Management, Ecosystem Science and Conservation
  • Laura Toledo, Master of Environmental Management, Ecosystem Science and Conservation

/undergraduate Team Members

  • Christina Boxberger, Environmental Sciences (BS)
  • Sara Haas
  • Maiya Hayes
  • Jessica Lipschultz

/yfaculty/staff Team Members

  • Justin Wright, Arts & Sciences-Biology

/zcommunity Team Members

  • Gabon Parks Agency
  • Research Institute of Tropical Ecology
  • Omar Bongo University