Mountain gorillas and freshwater cichlids in the western branch of the East African rift valley depend on the same fragile surrounding—a thriving ecosystem around Lake Kivu.
Natural hazards and a large refugee population around the lake that borders Rwanda and the Democratic Republic of Congo have compromised the region's biodiversity and sustainability. Depletion of the highland forests for fuel use and subsistence farming has claimed wildlife habitat and degraded streams. Likewise, efforts by Rwanda and the Congo to extract methane at the bottom of the lake to produce needed electricity for the region are proceeding with only a partial understanding of the risk of catastrophic degassing from the interplay of natural events and human activities. In addition to the volcanic Virunga Mountains that dam the basin to the north, are the numerous active fault lines in the region, which have the potential to set off catastrophic degassing of the lake's immense methane and carbon dioxide reserves.
Anthony Vodacek, a scientist specializing in remote sensing at Rochester Institute of Technology, is leading a two-year survey of the Lake Kivu system to collect scientific measurements for benchmarking hazards threatening the region's biodiversity. A $350,000 grant from the MacArthur Foundation is supporting the multidisciplinary effort.
"The overarching goal of our project is to understand the interplay and feedbacks between volcanism, faulting and biological processes and human activities on the Lake Kivu system over the past 5,000 to 10,000 years of volcanism, faulting and climate change," says Vodacek, a professor in RIT's Chester F. Carlson Center for Imaging Science. "We also will establish a baseline for assessing future human-induced and tectonic-induced change in the Lake Kivu rift system."
The comprehensive approach to evaluating different aspects of the ecosystem hinges on the varied expertise of Vodacek's team. Seismologist and volcanologist Cindy Ebinger, from the University of Rochester, and aquatic biologist Robert Hecky, at the University of Minnesota, Duluth, will head research teams on shore and on the lake, complementing Vodacek's analysis of satellite imagery.
Understanding the natural hazards is important to protecting the biodiversity in a place where endangered gorillas inhabit the highland forests on the flanks of active volcanoes, and ancestral species to a popular aquarium fish (haplochromine cichlids) swim far below in the crystal-clear waters of Lake Kivu.
"Our surveys will inform a broad range of development issues in Rwanda and neighboring countries, provide opportunities for training. They form the foundation for science-based policies regarding natural resource use, overuse, protection and recovery in the region," Vodacek says. "The biodiversity there is supported by the unique highland forest in that area," he says. "That is ground zero for the mountain gorillas. That is the one place where they live."
The multidisciplinary study involves a major survey of Lake Kivu, seismic and geodetic monitoring, and analyses of satellite imagery:
Lake Studies and Coring Survey—Hecky will seek to understand how methane is formed in the lake, how much is produced and at what rate, and—most important—determine whether or how often the lake has suffered catastrophic explosions in the past. Recent efforts by the Rwandan and Congolese governments to develop the underwater resource as a fuel source could temper the potential dangers associated with a gas-charged lake.
"Successful gas extraction will decrease the hazard as long as it doesn't upset the stability of the lake," Vodacek says. "The Rwandan government has already required hazard assessments, and they are full partners in our systems-based approach to hazard assessment and mitigation. They are showing due diligence in trying to understand what their extraction system does to the lake stability."
Hecky, Stephanie Guildford and Sergei Katsev of the University of Minnesota, Duluth, will make critical biological and chemical measurements of the water to help understand the production of methane in the lake. Hecky will sample lake sediments throughout the lake basin, extending analyses he first made on sediment cores extracted in 1971 and 1972. His early findings showed the occurrence of catastrophic lake overturns approximately every 1,000 years, perhaps resulting from earthquakes, landslides or volcanic eruptions agitating and releasing the methane from the bottom layers of the lake. Chris Scholz, at Syracuse University, will profile the sediments and crust beneath Lake Kivu to map lake bottom volcanic vents and faults, and to provide a context for the University of Minnesota, Duluth, team's cores and water samples. Together they will assess the long-term changes in the physical structure of the sediment and bedrock under the lake. Hecky's group and Scholz will take measurements on the lake in December and January 2011 using specialized equipment on Scholz's vessel, which has been used to explore other African lakes.
Monitoring Earthquakes and Volcanoes—Ebinger will install Global Positioning System sensors and seismometers to map shallow magma reservoirs and active faults, identify regions of volcanic degassing and create an earthquake database to evaluate earthquake and volcanic hazards in Rwanda and in the rift valley. These results will provide a basis to evaluate the geothermal potential of the Virunga Volcanic Province, and extend the lake bottom mapping to the rift margins onshore. She will train Rwandan scientists and students to use, install and maintain the equipment. The US-Rwandan team will then prepare, for the first time, maps of active faults, magma reservoirs and hazard zones to guide future development.
Remote Sensing Analysis of Deforestation—Analyzing satellite images of the entire region from 1972 to the present will reveal the extent of deforestation, habitat loss and the impact on regional stream and lake-water quality. Loss of forest canopy and intensity of land use rose with the increased population of people seeking refuge from political conflict. Bikash Basnet, a doctoral student in RIT's Center for Imaging Science, will look at data available through the Landsat satellite program in conjunction with higher resolution images. Vodacek will conduct field studies on the ground to better understand the satellite imagery in collaboration with Rwandan scientists in the Centre for Geographic Information Systems at the National University of Rwanda.
"The Rwandan government recently announced a big reforestation program," Vodacek says. "It's something we can contribute to, particularly regarding the water quality in the streams. Many forests are gone and the degraded land cover compromises the stream water quality. It impacts the access to clean water, promotes the spread of disease, and it impacts, potentially, the fish that live in this region.
"Overturns in the past upset the lake and the cichlids were able to find refuge in the streams. Now the stream water has been so degraded that those fish might have a difficult time finding refuge there. All of the other East African cichlids were derived from the ones in Lake Kivu."
Similarly, the mountain gorillas were broadly distributed in the past, but now depend on the Lake Kivu region as their sole refuge. The species may now be at risk of extinction from geological events that represented only local setbacks to the population in the past.
The team's effort to document the scientific baseline of the Lake Kivu region grew from a workshop Vodacek, Ebinger and Hecky held in Rwanda in January 2010 to address growing concerns about the natural dangers of Lake Kivu. Vodacek's liaison in the Rwandan government, Marie Christine Gasingirwa, director of science and technology in the Rwandan Ministry of Education, has invited local scientists and students from Kigali Institute of Science and Technology, the National University of Rwanda and INES-Ruhengeri to participate in the study.
"Involving our Rwandan colleagues is important to us in terms of building long-term relationships there," Vodacek says. "Developing the capacity of Rwandan scientists to apply lessons learned from these research projects to other issues in preserving these unique environments will be a welcome outcome."
The scientists will share findings from their study at a conference in 2013 in Kigali, Rwanda.