In Africa, elephants help with carbon stock in forests

Threatened with extinction, the African forest elephant plays a major role in African biodiversity. An international study with the participation of Brazilian researchers concluded that the animal promotes changes in forest structure and contributes to increase carbon storage.

Normally treated as a “gardener” animal, due to feeding and leaving seeds of several trees in the forests, there have not been studies on all the impacts of the action of these elephants on the African forests.

According to Simone Aparecida Vieira, a researcher at the State University of Campinas (Unicamp), the tropical forests in Central Africa have higher carbon stocks than those in the Amazon Rainforest, even in climatic and soil conditions similar.

“We observed that the presence of the elephant in a density of 0.5 to 1 animal per square kilometer increases the biomass above the ground in 26 to 60 tons per hectare of the forest. The results support the hypothesis that their presence may have shaped the structure of Africa’s rainforests and probably played an important role in differentiating them from the rainforests of the Amazon,” the researcher explains.

How does the elephant act?

In addition to feeding on the fruits, the elephant may scratch, run over or even knock down trees located near the trails it uses to cross the forest. This action reduces their density over time.

The decrease in tree density alleviates competition for water, light, and space between them, as well as favoring the emergence of larger trees with larger diameter and density of wood and, consequently, more carbon stored in the biomass.

This change in the structure of African rainforests and the composition of tree species influenced by the animal also increases the balance of above-ground biomass in the long term, the study said. “The presence of elephants in the tropical forests of Central Africa may have contributed to explaining these differences in relation to the Amazon in long periods of time,” said Simone Vieira.

How was the study conducted?

The researchers involved in the study made use of a computational model of ecosystem dynamics. Capable of tracking the dynamics of the structure and function of the ecosystem on a fine scale, the model simulates the horizontal and vertical heterogeneity of vegetation in the forest succession and, in the long term, the competition of plants for resources that lead to mortality. In addition, it analyzes how random events of disturbance, such as the presence of elephants, can influence forest structure in the short, medium and long term.

After the collection, the data were compared with two forests in the Congo Basin, one with elephants, the other without. The results indicate that the introduction of elephants causes a temporary effect of reducing the concentration of biomass above the soil of the forests, in a scale of 125 to 250 years, due to the increase of the mortality of small trees by the animal. The increase and successive equilibrium of above-ground biomass concentration is reached between 250 and 1,000 years after the introduction of the animals.

The study included researchers from Italian, French and North American universities, as well as Brazilians from Unicamp and Embrapa Informática Agropecuária.

The risks and impact of extinction

Under threat of extinction, the researchers also simulated the risks of losing the animal. The data collected showed that this would result in a decrease of 7% of above-ground biomass and up to 3 billion tons of carbon. Conservation of elephants can reverse this trend of falling carbon storage service estimated at $ 43 billion, say researchers.

“Our simulations suggest that if the loss of elephants continues unabated, Central African forests can release the equivalent of several years of CO2 emissions from fossil fuels from most countries, potentially accelerating climate change,” said Fabio Berzaghi, from the Laboratory of Environmental Sciences and Climate (CEA), France, and lead author of the study, in a statement from the institution.

The elephant population of the forest has fallen dramatically since the colonization of West Africa by the Europeans when the animals were hunted to obtain ivory. Today, elephant species have declined to less than 10% of their original number.

With information from Elton Alisson of Agência FAPESP