Large herbivores, such as elephants, can have important effects on ecosystems and biogeochemical cycles. Yet, the influence of elephants on the structure, productivity and carbon stocks in Africa’s rainforests remain largely unknown. Here, we quantify those effects by incorporating elephant disturbance in the Ecosystem Demography model, and verify the modelled effects by comparing them with forest inventory data from two lowland primary forests in Africa. We find that the reduction of forest stem density due to the presence of elephants leads to changes in the competition for light, water and space among trees. These changes favour the emergence of fewer and larger trees with higher wood density. Such a shift in African’s rainforest structure and species composition increases the long-term equilibrium of aboveground biomass. The shift also reduces the forest net primary productivity, given the trade-off between productivity and wood density. At a typical density of 0.5 to 1 animals per km2, elephant disturbances increase aboveground biomass by 26–60 t ha−1. Conversely, the extinction of forest elephants would result in a 7% decrease in the aboveground biomass in central African rainforests. These modelled results are confirmed by field inventory data. We speculate that the presence of forest elephants may have shaped the structure of Africa’s rainforests, which probably plays an important role in differentiating them from Amazonian rainforests.
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The ED2 model code is available at https://github.com/fabeit/ED2/tree/master/ED/src.
Gill, J. L. Ecological impacts of the late Quaternary megaherbivore extinctions. New Phytol. 201, 1163–1169 (2014).
Bakker, E. S. et al. Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation. Proc. Natl Acad. Sci. USA 113, 847–855 (2016).
Malhi, Y. et al. Megafauna and ecosystem function from the Pleistocene to the Anthropocene. Proc. Natl Acad. Sci. USA 113, 838–846 (2016).
Berzaghi, F. et al. Assessing the role of megafauna in tropical forest ecosystems and biogeochemical cycles—the potential of vegetation models. Ecography 41, 1934–1954 (2018).
Owen-Smith, N. Pleistocene extinctions: the pivotal role of megaherbivores. Paleobiology 13, 351–362 (1987).
The IUCN Red List of Threatened Species (IUCN, 2018); http://www.iucnredlist.org/
Guldemond, R. & Van Aarde, R. A meta-analysis of the impact of African elephants on savanna vegetation. J. Wildl. Manage. 72, 892–899 (2008).
Maisels, F. et al. Devastating decline of forest elephants in Central Africa. PLoS ONE 8, e59469 (2013).
Hawthorne, W. D. & Parren, M. P. E. How important are forest elephants to the survival of woody plant species in Upper Guinean forests? J. Trop. Ecol. 16, 133–150 (2000).
Blake, S., Deem, S. L., Mossimbo, E., Maisels, F. & Walsh, P. Forest elephants: tree planters of the Congo. Biotropica 41, 459–468 (2009).
Beaune, D., Fruth, B., Bollache, L., Hohmann, G. & Bretagnolle, F. Doom of the elephant-dependent trees in a Congo tropical forest. For. Ecol. Manage. 295, 109–117 (2013).
Lewis, S. L. et al. Above-ground biomass and structure of 260 African tropical forests. Phil. Trans. R. Soc. Lond. B 368, 20120295 (2013).
Avitabile, V. et al. An integrated pan-tropical biomass map using multiple reference datasets. Glob. Change Biol. 22, 1406–1420 (2016).
Terborgh, J. et al. The African rainforest: odd man out or megafaunal landscape? African and Amazonian forests compared. Ecography 39, 187–193 (2016).
Farrior, C. E., Bohlman, S. A., Hubbell, S. & Pacala, S. W. Dominance of the suppressed: power-law size structure in tropical forests. Science 351, 155–157 (2016).
Medvigy, D., Wofsy, S. C., Munger, J. W., Hollinger, D. Y. & Moorcroft, P. R. Mechanistic scaling of ecosystem function and dynamics in space and time: Ecosystem Demography model version 2. J. Geophys. Res. Biogeosci. 114, G01002 (2009).
Blake, S. & Inkamba-Nkulu, C. Fruit, minerals, and forest elephant trails: do all roads lead to Rome? Biotropica 36, 392–401 (2004).
Wing, L. D. & Buss, I. O. Elephants and Forests. Wildl. Monogr. 19, 3–92 (1970).
Omeja, P. A. et al. Changes in elephant abundance affect forest composition or regeneration? Biotropica 46, 704–711 (2014).
Poulsen, J. R. et al. Poaching empties critical Central African wilderness of forest elephants. Curr. Biol. 27, R134–R135 (2017).
Reich, P. B., Walters, M. B. & Ellsworth, D. S. From tropics to tundra: global convergence in plant functioning. Proc. Natl Acad. Sci. USA 94, 13730–13734 (1997).
Huang, S., Bartlett, P. & Arain, M. A. Assessing nitrogen controls on carbon, water and energy exchanges in major plant functional types across North America using a carbon and nitrogen coupled ecosystem model. Ecol. Model. 323, 12–27 (2016).
Wright, S. J. et al. Functional traits and the growth–mortality trade-off in tropical trees. Ecology 91, 3664–3674 (2010).
Milner-Gulland, E. J. & Beddington, J. R. The exploitation of elephants for the ivory trade: an historical perspective. Proc. R. Soc. Lond. B 252, 29–37 (1993).
Michelmore, F., Beardsley, K., Barnes, R. F. W. & Douglas-Hamilton, I. A model illustrating the changes in forest elephant numbers caused by poaching. Afr. J. Ecol. 32, 89–99 (1994).
Pillet, M. et al. Disentangling competitive vs. climatic drivers of tropical forest mortality. J. Ecol. 106, 1165–1179 (2018).
Poorter, L. & Bongers, F. Leaf traits are good predictors of plant performance across 53 rain forest species. Ecology 87, 1733–1743 (2006).
Ferry, B., Morneau, F., Bontemps, J.-D., Blanc, L. & Freycon, V. Higher treefall rates on slopes and waterlogged soils result in lower stand biomass and productivity in a tropical rain forest. J. Ecol. 98, 106–116 (2010).
Maley, J. et al. Late Holocene forest contraction and fragmentation in central Africa. Quat. Res. 89, 43–59 (2018).
Osuri, A. M. et al. Contrasting effects of defaunation on aboveground carbon storage across the global tropics. Nat. Commun. 7, 11351 (2016).
Doughty, C. E. et al. Global nutrient transport in a world of giants. Proc. Natl Acad. Sci. USA 113, 868–873 (2016).
Friedlingstein, P., Cadule, P., Piao, S. L., Ciais, P. & Sitch, S. The African contribution to the global climate-carbon cycle feedback of the 21st century. Biogeosciences 7, 513–519 (2010).
State and Trends of Carbon Pricing 2018 (World Bank, 2018).
Moorcroft, P. R., Hurtt, G. C. & Pacala, S. W. A method for scaling vegetation dynamics: the ecosystem demography model (ed). Ecol. Monogr. 71, 557–586 (2001).
Kalnay, E. et al. The NCEP/NCAR 40-year reanalysis project. Bull. Am. Meteorol. Soc. 77, 437–471 (1996).
Harmonized World Soil Database Version 1.2 (FAO, accessed 29 August 2018); http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/harmonized-world-soil-database-v12/en
Moore, S. et al. Forest biomass, productivity and carbon cycling along a rainfall gradient in West Africa. Glob. Change Biol. 24, e496–e510 (2018).
Terborgh, J., Davenport, L. C., Ong, L. & Campos-Arceiz, A. Foraging impacts of Asian megafauna on tropical rain forest structure and biodiversity. Biotropica 50, 84–89 (2017).
Blake, S. The Ecology of Forest Elephant Distribution and its Implications for Conservation PhD thesis, Univ. Edinburgh (2003).
Ssali, F., Sheil, D. & Nkurunungi, J. B. How selective are elephants as agents of forest tree damage in Bwindi Impenetrable National Park, Uganda? Afr. J. Ecol. 51, 55–65 (2013).
Terborgh, J. et al. Megafaunal influences on tree recruitment in African equatorial forests. Ecography 39, 180–186 (2016).
Struhsaker, T. T. et al. Tree mortality in the Kibale Forest, Uganda: a case study of dieback in a tropical rain forest adjacent to exotic conifer plantations. For. Ecol. Manage. 29, 165–185 (1989).
White, L. J. T., Tutin, C. E. G. & Fernandez, M. Group composition and diet of forest elephants, Loxodonta africana cyclotis Matschie 1900, in the Lopé Reserve, Gabon. Afr. J. Ecol. 31, 181–199 (1993).
Schuttler, S. G., Blake, S. & Eggert, L. S. Movement patterns and spatial relationships among African forest elephants. Biotropica 44, 445–448 (2012).
Carroll, R. Status of the lowland gorilla and other wildlife in the Dzanga-Sangha region of southewestern Central African Republic. Primate Conserv. 7, 38–41 (1986).
Morgan, B. J. Group size, density and biomass of large mammals in the Réserve de Faune du Petit Loango, Gabon. Afr. J. Ecol. 45, 508–518 (2007).
White, L. J. T. Biomass of rain forest mammals in the Lopé Reserve, Gabon. J. Anim. Ecol. 63, 499–512 (1994).
Poulsen, J. R., Clark, C. J. & Palmer, T. M. Ecological erosion of an Afrotropical forest and potential consequences for tree recruitment and forest biomass. Biol. Conserv. 163, 122–130 (2013).
Slik, J. W. F. et al. Large trees drive forest aboveground biomass variation in moist lowland forests across the tropics. Glob. Ecol. Biogeogr. 22, 1261–1271 (2013).
Chave, J. et al. Improved allometric models to estimate the aboveground biomass of tropical trees. Glob. Change Biol. 20, 3177–3190 (2014).
Chave, J. et al. Towards a worldwide wood economics spectrum. Ecol. Lett. 12, 351–366 (2009).
Lewis, S. L. et al. Increasing carbon storage in intact African tropical forests. Nature 457, 1003–1006 (2009).
Lima, R. A. F., Muller-Landau, H. C., Prado, P. I. & Condit, R. How do size distributions relate to concurrently measured demographic rates? Evidence from over 150 tree species in Panama. J. Trop. Ecol. 32, 179–192 (2016).
We would like to thank: F. Berzaghi’s PhD thesis committee: D. Papale, M. Zapparoli and L. Portoghesi; A. Swann and S. Wasser for their conception of this idea and their mentorship during initial work on the project; and M. di Porcia e Brugnera and H. Verbeeck for the feedback that helped improve the manuscript. We thank the contributors to the AfriTRON network for making their data publicly available, J. Poulsen, G. van der Heijden and the TEAM Network in particular. We thank the Institut Congolais pour la Conservation de la Nature for granting permission to conduct research at LuiKotale, and Lompole villagers for granting permission to access the forest of their ancestors. We thank the government of the Republic of Congo for permission to study elephant ecology in the Ndoki forest and the Wildlife Conservation Society for invaluable support in the field. F.Berzaghi was funded by the CEA Enhanced Eurotalents Fellowship (a Marie Sklodowska-Curie Actions Programme) and the University of Tuscia doctoral programme. We thank the Centre de Calcul et Messageries, Pôle des Systèmes d’Information et des Usages du Numérique Université de Bourgogne for the assistance with and use of their cluster. Research at LuiKotale was supported by the Max-Planck-Society, the German Ministry of Education and Research and le Conseil Regional de Bourgogne. We thank the African Elephant Program of the United States Fish and Wildlife Service for supporting data collection in the Ndoki Forest and USAID for funding.
The authors declare no competing interests.
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Berzaghi, F., Longo, M., Ciais, P. et al. Carbon stocks in central African forests enhanced by elephant disturbance. Nat. Geosci. 12, 725–729 (2019). https://doi.org/10.1038/s41561-019-0395-6
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