Over the past 20 years, people living in the forests of Congo Basin have noticed some significant changes in their natural surroundings, according to scientists. Not only is the area becoming hotter, but there is greater variability in the length and intensity of the rainy season, they report.
Less precipitation leads to dryer conditions, reducing water flow and creating challenging and unpredictable circumstances for rural communities whose livelihoods depend on local forests and waterways.
About 100 million people live in the Congo Basin, which is located in west equatorial Africa and spans six countries. The Congo River and smaller veins of freshwater course through the region, accounting for 30 percent of freshwater on the continent, and providing hydrological balance for the local and regional climate.
Scientists with the Center for International Forestry Research (CIFOR) estimate that as much as 95 percent of rainfall in the area results from the recycling of moisture from forests.
The lush tropical ecosystem feeds unique biodiversity, providing habitats for hundreds of varieties of fish, snails, frogs and other aquatic species, many of which contribute to local diets. As a vast carbon sink, the basin contributes as a counterweight to global warming and climate change, experts say.
To learn more about the consequences of hydrological modification on livelihoods in the region, Denis Sonwa, a senior scientist at CIFOR based in Cameroon, conducted research into three areas of the basin, producing profiles based on field studies, pre-existing data and interviews conducted with local people.
The idea behind the project was to help inform strategic environmental and economic policies, said Sonwa. He has formerly studied hydro-climatic variability and its impact on the rural economy and livelihoods as head of CIFOR’s Congo Basin Forests and Climate Change Adaptation (COFCCA) project for which fieldwork was conducted between 2000 and 2010.
“Climate adaptation and mitigation measures can’t be designed or put in place without a better understanding of the dynamics of ecosystem changes,” he said.
Scientists carried out field research in the So’o watershed in Cameroon, the Mpoko watershed in Central African Republic (CAR) and in the community of Masako on the outskirts of Kisangani in Democratic Republic of Congo (DRC) between 2008 and 2010.
“We dug deeper into the potential consequences of water flow disturbances on livelihoods,” said Sonwa, whose team — which included scientists from Cameroon’s University of Yaounde, CAR’s University of Bangui and DRC’s University of Kisangani — measured changes in moisture.
They crunched data on trends observed in temperatures, precipitation, water flows and water quality to determine the implications for local livelihoods and the economy.
It became clear that the number of caterpillars in the Mpoko watershed had dropped dramatically in 2009. The insects, which are the main source of food in the local villages, appeared earlier in the year than usual and when they did, they were smaller and had a shorter lifespan. Households living in the savanna woodland gathered an average of 20 kg of caterpillars, compared to a former average of 145 kg, a loss of 86.2 percent.
That same year, the availability of mushrooms in the area also plummeted, the researchers learned. On average, households gathered 10 kg compared to a former average of 85 kg, an 88.2 percent decrease.
Along the Mpoko River – a small offshoot of the Oubangui River, which is a major tributary of the Congo River – fishers complained of a dramatic drop in stock.
In the Mpoko watershed, the average annual temperature increased about 1 degree from roughly 26 degrees Celsius to a little over 27 degrees Celsius between 1990 and 2015, an average increase of about 3 percent each decade, according to the scientists, who reported their findings in Sustainability journal. The rainy season now starts earlier, and more rain falls in December, while February is now generally dry.
These changes also create havoc for farmers whose fields may not be ready for planting in time to catch the benefits of the rains or who may plant prematurely not anticipating their delay. Variations in the norm mean they can lose their harvest due to being unaware they should plant different crops.
“This kind of irregularity is now characteristic of the region, and often leads to poor harvests,” Sonwa said.
The scientists found a similar story in So’o watershed, where annual temperatures were around 24 degrees Celsius in 1980, but have increased on average about half a degree at a rate of about 1.7 percent to 2010. Rainfall averages fluctuate in rainy and wet seasons, and about 75 percent of people told the scientists they had been affected.
“The watershed has experienced climatic disturbances, which influence the start of the rainy season and the amount of precipitation, degrading the water cycle,” Sonwa said. “This has led to a decrease in water supply, which has been detrimental to farming and reduced aquatic biodiversity – particularly the availability of fish.”
Masako has also experienced a decrease in caterpillars, snails, mushrooms and wild fruit, according to the research. In Masako, the average annual temperature was 24.5 degrees Celsius between 1971 and 2001, but subsequently rose to 27.3 degrees Celsius after that year. In general, during the 30-year timespan, precipitation decreased by 48 mm and temperature increased by 2.8 degrees Celsius. In this area, farmers reported that a longer, dryer season led to less agricultural, aquatic and forest production.
“In this area, we found that agricultural species were disrupted due to their inability to reproduce in higher temperatures or due to a complete lack of water where rivers dried up,” Sonwa said.
Another consequence of the area becoming warmer and dryer as the water cycle becomes more unstable due to climate change in Masako is a reduction in water quality. Springs are often polluted and abandoned due to forest degradation caused by the proximity of farms and households.
The loss means that women and children have to walk long distances – often twice daily — to collect and carry 20 kg containers of drinking water from clean springs in forests.
“We observed that the water cycle in forests is gradually changing — in turn, ecology, biodiversity and resource-dependent livelihoods are being negatively affected,” Sonwa said. “Our findings confirm what the U.N. Intergovernmental Panel on Climate Change has previously reported – that tropical rainfall in Africa is decreasing.”
Long term projections indicate that precipitation could decrease by 17 percent by 2090, the CIFOR scientists report in the paper, citing sources. Less rain results in lower surface and groundwater flows and watersheds generate less water during periods of low rains.
These changes in drinking water, agriculture and non-timber forest products, have negative implications for food security and health, pointing to the need to address adaptation to climate change at the watershed level as a multi-sectoral challenge.
“Lack of development infrastructure makes the population more vulnerable,”Sonwa said.
Efforts to promote sustainable management of forests in the region are underway by the Central Africa Commission on Forests (COMIFAC), which works within the REDD+ (Reducing Emissions from Deforestation and forest Degradation) framework, a policy initiative adopted at U.N. climate talks in 2013 and recognized under the U.N. Paris Agreement in 2015 toward sustainable management of forests. The International Congo Ubangui Sanga Commission (CICOS) is working on water-specific strategies.
“Overall, we need to conduct more research by working with communities to ensure livelihoods remain sustainable,” Sonwa said. “We recommend that policymakers consider these changes in watersheds when implementing development and environmental actions in the Congo Basin.”
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