PhD student Evan Hockridge recently led a field expedition to Odzala-Kokoua National Park in the Republic of Congo with Professor Andrew Davies and Tom Lautenbach (drone pilot and field technician). Evan's PhD seeks to understand the specific ways that large animals influence the structure and composition of Central African forests via ecosystem engineering and alterations to ecosystem functioning. Afrotropical rainforests are ecologically unique among rainforests around the world. Despite having lower stem density, Central African forests have larger trees with higher wood densities on average than both the Amazonian and Asiatic rainforests. The result is that Congolese rainforests are among the most carbon dense in the world, making them extremely important to maintain during this era of climatic change. Despite their importance, very little is understood regarding why these forests have such a unique structure. Some have suggested that the presence of megafauna, which have been mostly lost in the other rainforests in the world, may be the cause - but a mechanism for this has not been clearly identified.
The field trip was focused around surveying bais, or giant saline forest clearings, that are unique to Central Africa with the Harvard Animal Landscape Observatory (HALO). Bais, despite comprising less than 1% of the national park's 13,468 km2, are critical resources that influence the activities of virtually all of the animal species in the park. Forest megafauna, such as forest elephants and western lowland gorillas, spend their lives traveling between the bais for mineral resources and social opportunities via trail networks engineered over centuries. While long assumed by many to be either created or maintained by megafauna, our research is the first to attempt to understand how and to what extent animals create and maintain these mysterious landscape features.
Following this project, Evan's future work in the park will expand outward from the bais to understand how these animals influence the demographics and composition of the surrounding forests and to predict the carbon storage implications of these endangered ecosystem engineers and what would be at stake if they were to go extinct.
The trip required operating complex drone aircraft in challenging environments.The team traveled by car, boat, and airplane around the park to reach various survey sites. Many of these sites required carrying over 200kgs of equipment up to 12km round trip per day between the bais and remote campsites.