Climate Change affects fish stocks in Lake Bosomtwi
The change in climate appears to have affected Lake Bosomtwe, with many youth in the area, who depend on it for survival, migrating to the towns and cities to seek for greener pastures because the fish stock has dwindled, from how it used to be in the past.
The youth, who are in the age bracket of 18-25 years, hail from communities such as Obo, Pepie and others, dotted along the lake.
Scientific evidence indicate that heavily fished zones in the Bosomtwe lake have less catches, while other zones have high concentration of juvenile fishes due to less fishing.
These findings were made known at a stakeholders’ meeting held at Abono in the Bosomtwe District, which was organised by the RELAB project and funded by the Ministry of Foreign Affairs of Denmark through Danida.
RELAB presented five scientific reports at the meeting, revealing how climate change and human activities are contributing to the present dire state of the lake.
Held under the theme: “Strengthening Partnerships for Building the Resilience of Lake Bosomtwe to Climate Change”, the event brought together participants such as – Water Resources Commission, Environmental Protection Agency (EPA), Ghana Tourism Authority, Fisheries Commission, A ROCHA Ghana, Bosomtwe District Assembly, Bosome-Freho District Assembly and others, to discuss how the lake can be governed effectively to promote long term sustainable management.
The five-year RELAB project, which started in 2018, will end in 2022. It is an international collaborative research project of scientists from Ghana, Denmark and Germany.
In another scientific finding which was presented at the meeting, it was established that there has been a gradual increase in atmospheric temperature and rainfall around Lake Bosomtwe, a development that has led to greater evapo-transpiration, resulting in low water levels.
The report forecasts that for the next ten years, the lake will likely recede if atmospheric pressure continues at the current rate, creating more bare lands from the receding lake, which will be used mostly for agriculture and building activities.
The intensified farming activities are, however, introducing toxic contaminants into the lake due to the application of pesticides, fertilizers and weedicides.
Dr Peter Sanful, a Limnologist at the University of Energy and Natural Resources (UENR) in Sunyani, who doubles as the Project Coordinator of RELAB, explained at the meeting that the ecosystem and livelihood of many people who live around the lake would be affected, because of climate change effect on the lake and the complexities associated with the negative adaptive responses of the people.
Explaining the fundamental ecological processes of the lake that are important in supporting fish production, Sanful noted that the lake is extremely sensitive to climate change and will, therefore, be heavily impacted by the phenomenon.
He further noted that atmospheric heat received by the lake is transported differently throughout the deep depth of the lake creating three layers of water masses that differ in water temperature. This condition is called stratification and is the most important physical mechanism driving the functioning of the lake.
Stratification, the UENR Limnologist noted, creates a density difference between the water masses.
According to him, due to persistent stratification of the lake, it is no longer “turning over” regularly during the cool season in August.
Dr Sanful further threw more light on how Lake Bosomtwe operates, explaining that during the cool season, which spans from July to August, the lake surface, because of reduced solar input, becomes colder and sinks, and once it sinks, it mixes up the whole water column and the nutrients that were accumulated in the bottom of the lake during stratification.
This ecological phenomenon, he continued, stimulates productivity and that is what the local people call ‘atuduro’, whereby the fish come to the surface of the lake from suffocation, then the local people trap them.
He revealed that from October to June, the lake is stratified. However, during July to August when the weather is cool, it turns over. This process is what sustains the fish but the atmospheric warming trend and climate change continues to heat the lake and prevents it from turning over.
“The risk of climate change is that it will keep the lake in a perpetual stratified condition, without mixing, so the productivity of the lake will continue to decline”, he said.
Touching on the ecosystems , Peter Sanful , explained that all over the world, ecosystems are known to be the foundation of human existence providing a range of services such as food, medicine etc beneficial to humans.
According to him, because of population growth and a whole lot of natural factors, the ecosystem of the lake is increasingly coming under threat from global natural environmental changes like climate change and high population growth.
Earlier, Prof. Emmanuel Opuni-Frimpong, Principal Researcher Scientist at CSIR Forestry Research Institute of Ghana noted in his keynote address that the RELAB Project will yield important scientific information urgently required for the sustainable management of the lake. He said: “All these require some continuous research effort to be able to help us to plan so that all the opportunities we have from Lake Bosomtwe would not be lost”.
According to Prof Opuni-Frimpong, Lake Bosomtwe contains one of the best preserved and informative records of past climate change in the world.
He said: “If we want to study climate change, we need some sort of key indicators in science that we can use to monitor and Lake Bosomtwe has been recognised as one of such places, where we can gather more information on climate change in the tropics. However, the lake is changing in a way that needs further research to establish how things are panning out.
Opuni-Frimpong further indicated that research conducted earlier reveals fish productivity in Lake Bosomtwe is strongly affected by climatic variation, via their control of the lake’s physical and chemical processes.
He noted that Lake Bosomtwe is a climate-sensitive lake that has been recognised by UNESCO as the World Heritage Site for its natural and cultural significance, adding that it is the only natural lake in Ghana and it is the oldest lake that we find in this part of the world and also the deepest in West Africa.
In a remark, the District Chief Executive of Bosomtwe District, Joseph Kwasi Asuming, indicated that people have been making attempts to get closer to the lake and build, but the Assembly has prevented them, by enforcing the 100 meters buffer zone stipulated in the District Assembly bye-laws on the lake.