Elephants are one of the few megaherbivores that survive today. Forest elephants shape the environment in which they live by dispersing seeds and acting as bulldozers, feeding on around a hundred different species of fruits, trampling bushes and felling trees. In this post, we already told you how elephants and frogs relate thanks to these activities.
The ecological impact of these activities therefore affects tree populations and carbon levels in the forest, which has significant implications for climate and conservation policies.
In a study conducted by Saint Louis University and published in Nature Geoscience, Central African forest elephant populations have been found to stimulate the growth of slow-growing trees. These trees have a high wood density and therefore sequester more carbon from CO2 in the atmosphere.
How do they influence CO2?
These pachyderms prefer to feed on fast-growing species, causing high levels of mortality and damage to these species compared to slow-growing, high-wood-density species.
The collapse of their populations could cause an increase in the abundance of fast-growing species at the expense of slow-growing species that are better able to fix CO2 from the atmosphere.
The author of the study, Stephen Blake, a professor of biology at Saint Louis University, spent 17 years in Central Africa working on elephant conservation. In addition, he collected data on the structure and composition of species in the Nouabalé-Ndoki forest of northern Congo.
What would happen to the composition of the forest over time without the presence of elephants?
To answer this question, they developed a mathematical model that assumed that elephants graze certain species at different rates. When they are in open spaces they prefer fast-growing plants, so as they feed and graze, they cause damage, breaking trees or bushes.
The model calculated feeding and breaking rates along with elephant mortality rates to see their effect on certain woody plants.
“As of right now, when we look at the number of elephants in a forest and look at the composition of forests over time, we find that the proportion of trees with high-density wood is higher in forests with elephants,” he said. Blake.
The simulation found that slow-growing plant species survive better when pachyderms are present. These species are not consumed by them and, over time, the forest becomes dominated by these slow-growing species. Wood (lignin) has a carbon backbone, meaning it has a large number of carbon molecules that come from atmospheric CO2.
Slow-growing, high-wood-density species contain more carbon molecules per unit volume than fast-growing, low-wood-density species. As elephants “thin” the forest, they increase the number of slow-growing species. Trees and forest are capable of storing more carbon.”
The reduction in forest stand density due to the presence of these animals leads to changes in competition for light, water and space between trees. These changes favor the appearance of fewer and larger trees with greater wood density. This change in African rainforest structure and species composition increases the long-term balance of aboveground biomass.
The extinction of this species would result in a 7% decrease in aboveground biomass in the rainforests of central Africa. These modeled results are confirmed by field inventory data, according to the study.
The authors speculate that the presence of forest elephants may have shaped the structure of African rainforests, likely playing an important role in differentiating the Amazon rainforests.
The need to protect them
These findings suggest far-reaching ecological consequences. The loss of this species will seriously reduce the remaining forest’s ability to sequester carbon. Trees and plants use CO2 during photosynthesis, removing it from the atmosphere. For this reason, plants are useful in combating global warming and serve to store carbon emissions.
Without forest elephants, less carbon dioxide will be removed from the atmosphere. In monetary terms, forest elephants represent a $43 billion carbon storage service.
“The sad reality is that humanity is doing everything it can to rid the planet of elephants as quickly as it can,” Blake said. “Forest elephants are declining rapidly and facing extinction. “From a climate perspective, all of their positive carbon effects and their countless other ecological roles as gardeners and foresters will be lost.”
The study’s authors point out that forest elephant conservation could reverse this loss. The biggest threats to this species are the loss of its habitat and poaching for the highly prized pink ivory from its tusks.
«Elephants are an emblematic species. People love elephants: we spend millions every year on stuffed animals, they’re zoo favorites, and who didn’t cry during Dumbo? And yet, we are bringing them closer to extinction every day. On the one hand, admire them, empathize and be horrified when they are murdered, and on the other hand we are not prepared to do anything serious about it. The consequences can be serious for everyone. We need to change our ways.
«Besides, it makes sense to keep them around. “They are doing an incredible job helping the planet store carbon for free.”