Changing Composition of African Tropical Forests

Changing Composition of African Tropical Forests

Africa hosts the second largest area of tropical forest in the world. Recent research has shown that remaining African tropical forests are changing, with global implications [1]. There is evidence that these forests have been increasing in carbon stocks, slowing the rate of climate change, in part, due to increasing tree growth from more carbon dioxide in the atmosphere [1]. Yet, little is known about how the composition of these forests is changing. This PhD project is to use long-term inventory plots as part of the African Tropical Rainforest Observatory Network ( to assess which species are the winners and which are the losers as forests have changed over the past three decades.

The successful student with use the ~400 long-term inventory plots in structurally intact forest, totaling ~200,000 individual tree stems, to assess how species composition has changed, and why they have changed over recent decades. The causes may be related to the impacts of drought increasing the proportion of drought-adapted species (as seen in Ghana, [2]), or high temperatures limiting some species (as possibly being seen in central Gabon, [3]), or due to changes in hunting pressure, particularly the loss of elephants (suggested in [4]). The student will use statistical techniques to address which species are proportionately increasing, which are decreasing, and whether the compositional changes seen are keeping up with the pace of climate change.

The project is relatively open, as so little is known about the changing composition of these forests.  I encourage students to ‘make the project their own’. The expectation is that the student will lead and publish ground breaking papers on African tropical forests.

While the PhD is computer-based, it is expected that the student will undertake two field campaigns to recensus inventory plots, one as part of a team where they will be trained, and a second where they will lead the expedition. This will contribute to the student understanding the biases that can affect long-term phytodemographic data, help the PhD project, and contribute to the long-term datasets that underpin studies such as these.

The student will expected to have either a biology, geography or mathematical background, with a strong interest in research.

Any questions, feel free to email me.


[1] Hubau W., Lewis, S.L. et al. 2020. Asynchronous carbon sink saturation in African and Amazonian tropical forests, Nature 579, 80-87

[2] Fauset, S., Baker, T.R., Lewis, S.L., Feldpausch, T.R., Affum-Baffoe, K., Foli, E.G., Hamer, K.C. & Swaine, M.D. (2012) Drought-induced shifts in the floristic and functional composition of tropical forests in Ghana. Ecology Letters, 15, 1120-1129; Jesús Aguirre-Gutiérrez, J., Malhi, Y., Lewis, S.L. et al. 2020. Long-term droughts may drive drier tropical forests towards increased functional, taxonomic and phylogenetic homogeneity. Nature Communications, 11, 3346.

[3] Bush, E.R. et al. 2020. Long-term collapse in fruit availability threatens Central African forest megafauna. Science, 24 Sept. eabc7791.

[4] John R. Poulsen, Cooper Rosin, Amelia Meier, Emily Mills, Chase L. Nuñez, Sally E. Koerner, Emily Blanchard, Jennifer Callejas, Sarah Moore, Mark Sowers, 2018. Ecological consequences of forest elephant declines for Afrotropical forests. Conservation Biology, 32, 559-567.