Is Natural Recovery Of A Tropical Forest In An Anthropogenic Savanna Possible?
Urbanization, timber exploitation, and the need for farmland has led to deforestation in Central Africa. A widespread technique to clear the dense vegetation is intentional burning. Not only does this prepare the land for farming, but it also attracts animals to the annual fresh vegetation. However, this repeated burning gives rise to anthropogenic savannas, while tropical forests are diminishing.
Tropical rainforests contain half the world’s vegetable carbon and play an essential role in the regulation of the climate by storing excess CO2 from the atmosphere. When this intentional burning is halted, it is possible that the tropical forest could return, however, little is known about the speed of tropical forest recovery. Determining this return rate is vital, especially with the increased interest and attention to REDD + – (Reduce Emission from Deforestation and forest Degradation) projects as well as supporting FLR (Forest Landscape Restoration) practices.
In 2005, the World Wildlife Fund (Belgium & Democratic Republic of Congo), the Laboratory of Wood Technology (Ghent University, Belgium), the Service of Wood Biology (Royal Museum for Central-Africa, Belgium), and the Institut National pour l’Etude et la Recherche Agronomique (the Democratic Republic of the Congo) set up an experiment to determine the tropical forest recovery rate and the carbon sequestration potential of fire exclosures. The research was conducted in a savanna patch at the southernmost border of the Mayombe forest, close the villages of Manzonzi and Mao, located near the UNESCO Man and Biosphere Reserve of Luki and approximately 30 km north of the City of Boma (Lower Congo Province, the Democratic Republic of the Congo). Within the 200-hectare Manzonzi savanna, the annual burning regime was stopped in an 88-hectare exclosure area and an agreement was made with the local people to prevent burning and grazing. In 2010, the first inventory took place over 37.2 hectares (based on permanent plots); every tree above a certain diameter was measured and tagged. In 2014, the same inventory of these plots took place.
Over a period of four years, the increase of typical forest species was 9 stems per hectare per year, while typical savanna species decreased with 16 stems per hectare per year. This already indicates that the savanna vegetation is disappearing while the forest encroachment is on the way. This encroachment depends on the forest species recruitment potential, which is enhanced by the presence of the Mayombe forest. The forest carbon recovery rate was estimated at 0.62 Mg C per hectare per year.
The current carbon stock in the exclosure was compared to the carbon stock of a tropical forest in the nearby Luki Biosphere Reserve (19 permanent plots). This showed that the carbon stock was still less than 5% of the average amount in the tropical rainforest. As such, it is estimated that the total forest carbon recovery will take at least 150 years. However, more censuses are needed to refine these long-term estimations.
The Manzonzi exclosure is a perfect example of how REDD + – projects can enhance both carbon sequestration and biodiversity. Reforestation initiatives are an important strategy in combatting climate change, and continued follow-up and the ongoing support of local communities are vital towards their success.
These findings are described in the article entitled Rate of forest recovery after fire exclusion on anthropogenic savannas in the Democratic Republic of Congo, recently published in the journal Biological Conservation.