Carbon Stocks and Climate Changes: Forest Elephants are the Elusive Protectors of the African Rainforest
Today poaching and deforestation are the major culprits for the 80% decrease in forest elephant populations in areas of Central Africa with the densest elephant populations¹. A recent study showed the vast influence of forest elephants on the structure, productivity, and carbon storing ability in the African rainforest². The long-term implications of these influences of climate change are extensive should elephants continue to disappear from these unique landscapes at the current pace.
Carbon stocks are closely linked to forest biomass³. Forest elephants play a critical part in maintaining this storage capacity. As they move about eating, stepping on, and otherwise decreasing the density of smaller trees and plant species, they open up areas with more light, water, and space among the larger trees. This allows fewer and larger trees to thrive — exactly the trees that store the most carbon!² Large trees capture more carbon from the air and reduce atmospheric CO2 and its greenhouse effects contributing to climate changes. The African rainforest is one of the most important carbon “sinks” for sequestering CO2 released into the atmosphere by many countries’ massive fossil fuel emissions⁴,⁵. However, scientists predict that the disappearance of forest elephant populations from this habitat may result in the loss of 3 billion tons of carbon — comparable to France’s total CO2 emissions for 27 years⁶.
So, how was this important observation discovered? Dr. Fabio Berzaghi led a team of scientists at the Laboratory of Climate and Environmental Sciences in France to quantify the effects of elephant disturbances on the African rainforest ecosystem and determine the future consequences of the species’ extinction². Berzaghi hypothesized that elephants may drive patterns of vegetative structure and diversity that distinguish the African rainforest from the Amazon rainforest. The Amazon, in comparison to the African rainforest, lost all of its large herbivores to extinction nearly 12,000 years ago⁶. The Amazon has since developed a higher density of small trees, an overall decrease in vegetation, and a reduced capacity to absorb carbon from the atmosphere⁴,⁶.
Dr. Berzaghi and his team measured the short-term effects of elephant disturbance by recording every tree species and trunk sizes at two field sites: Ndoki, Republic of Congo where elephant numbers are dwindling, and LuiKotale, Democratic Republic of Congo where elephants disappeared 30 years ago⁶. Long-term effects were then measured using a computer model that simulated the basic functions of the African rainforest including tree growth and death, competition, photosynthesis, and reproduction. They could then include or exclude elephant disturbances into the model⁶.
Dr. Berzaghi’s team discovered that by leveling trees smaller than 12 inches as they travel, forest elephants influence significant changes in competition for light, water, and space amongst tree species. Such ecosystem changes alter plant composition to favor a high forest biomass of fewer, but larger trees. Although these tree species grow slower, they compensate by investing in building high wood density using carbon. Should elephants become extinct, the scientists found, there would be a 7% decrease in forest biomass².
Forest elephants are smaller and more elusive than their savanna elephant counterpart, making them more difficult to study, but researchers are discovering that these creatures maintain biodiversity, aid in nutrient recycling, and promote growth of larger trees with higher carbon storing ability — an invaluable role in west and central African rainforests⁷.Although scientists do not know the extent of carbon losses already suffered due to elephant decline, steps such as stopping poaching and reducing human encroachment may be the most beneficial start to restoring elephant populations and their ecological and climate benefits.
References:
¹ Poulsen, John R., Sally E. Koerner, Sarah Moore, Vincent P. Medjibe, Stephen Blake, Connie J. Clark, Mark Ella Akou et al. “Poaching empties critical Central African wilderness of forest elephants.” Current Biology 27, no. 4 (2017): R134-R135. Retrieved from https://www.cell.com/action/showPdf?pii=S0960-9822%2817%2930024-6
² Berzaghi, Fabio, Marcos Longo, Philippe Ciais, Stephen Blake, François Bretagnolle, Simone Vieira, Marcos Scaranello, Giuseppe Scarascia-Mugnozza, and Christopher E. Doughty. “Carbon stocks in central African forests enhanced by elephant disturbance.” Nature Geoscience (2019): 1–5. Retrieved from https://www.nature.com/articles/s41561-019-0395-6.pdf
³ Janowiak, Maria, Swanston, Chris, Ontl, Todd. “Management of Forest Carbon Stocks.” U.S. Department of Agriculture, Forest Service, Climate Change Resource Center (2017). Retrieved from https://www.fs.usda.gov/ccrc/topics/forest-mgmt-carbon-benefits/carbon-stocks
⁴ Radford, Tim. “Amazon rainforest is losing carbon storage capacity.” Climate Home News (2015). Retrieved from https://www.climatechangenews.com/2015/03/19/amazon-rainforest-is-losing-carbon-storage-capacity-study/
⁵ “Forest Elephant.” African Wildlife Foundation. Retrieved from https://www.awf.org/wildlife-conservation/forest-elephant
⁶ Nuwer, Rachel. “The thick gray line: Forest elephants defend against climate change.” The New York Times (2019). Retrieved from https://www.nytimes.com/2019/08/19/science/elephants-climate-change.html
⁷ Poulsen, John R., Cooper Rosin, Amelia Meier, Emily Mills, Chase L. Nuñez, Sally E. Koerner, Emily Blanchard, Jennifer Callejas, Sarah Moore, and Mark Sowers. “Ecological consequences of forest elephant declines for Afrotropical forests.” Conservation biology 32, no. 3 (2018): 559–567. Retrieved from https://conbio.onlinelibrary.wiley.com/doi/pdf/10.1111/cobi.13035
