An Assessment of the Impacts of Climate Change and Land-use Patterns on Surface Water Quantity and Quality, Fisheries Resources and the Ecosystem Services of Fisheries Dependent Livelihoods in a Downstream peri-urban Lake System in Zimbabwe

Utete, Beaven (2018)


Peri-urban lakes support fishing dependent livelihoods but are amongst the most degraded and overutilised freshwater ecosystems. Fluctuating climatic and non climatic variables threaten water quantity, quality, and beneficial ecosystem services utilised by fishing communities in Lakes Chivero and Manyame in Zimbabwe. This study aimed to:(i) establish changes in climatic factors and land use patterns in the catchment of Lakes Chivero and Manyame (ii) investigate the impacts of climate change and land use patterns on water quantity, quality and fish catches, (iii) determine the levels of selected heavy metals in water and sediments and their accumulation in the tissues of two fish species, Clarias gariepinus (catfish) and Oreochromis niloticus (Nile tilapia) and the potential ecological risks posed under a changing climate (iv) assess the perceptions, livelihood strategies and the vulnerability and adaptive capacity of fishing dependent communities to climate change in Lakes Chivero and Manyame in Zimbabwe. Data on morphometric parameters, water quantity and hydrodynamics, land use patterns and historical fish catches of the two lakes was collected using satellite based geographic information systems (GIS) and from secondary sources. Field sampling was done to collect water, sediments and fish in Lakes Chivero and Manyame in November 2015-November 2016. Key informant interviews, focus group discussions and questionnaires were used to collect socioeconomic data for fishers at a total of 23 cooperatives sampled in the two lakes. There is evidence of climate change as reflected by significant (p<0.05) changes in windspeeds, average humidity and evapotranspiration, though there were no significant changes in temperature and rainfall amounts over 1983-2015 in the Manyame catchment. Land use patterns have significantly (p<0.05) changed in the Manyame catchment with increases observed for barelands and other areas, built up areas and croplands, and decreases in spatial extent were noted for irrigation lands, grasslands, water covered areas and forests and shrubs. Water levels in Lakes Chivero and Manyame have significantly increased (Sen Slope>0, p<0.05) over the same period. Climatic factors and land use patterns have a significant interactive influence on the water levels of the two lakes. Heavy pollution levels, especially for aluminium (Al), iron (Fe), cadmium (Cd), zinc (Zn), chromium (Cr) and copper (Cu) were detected in water and sediments of both lakes. Some metals particularly Al, Zn, Cr and Pb accumulate in the tissues of the two fish species in both lakes. Metal pollution and its accumulation arises from anthropogenic and geogenic sources in the Manyame catchment, however, climate change and continuing pollution poses an ecological risk for aquatic organisms and humans as they consume the contaminated fish in Lake Chivero and Lake Manyame. Fish catches have decreased in Lakes Chivero and Manyame resulting in loss of indigenous species and a shift towards a monotone species scenario with O. niloticus dominating over the last two decades. The interactive effects of climatic factors, land use patterns and water levels significantly influence fish catches in both lakes. Fisheries and fisherfolks are exposed and sensitive and vulnerable to a combination of climate change, and non climatic factors such as water quantity and quality deterioration. Over 94% (n = 82) of fisherfolks acknowledge climate change and its impacts on the water resources and their livelihoods in Lakes Chivero and Manyame. The main livelihood strategies for fisherfolks comprise of fishing ie 54% (n = 47) with the rest 46% (n = 40) living diversified livelihoods dominated by climate sensitive strategies like farming. Fisherfolks are vulnerable, as fishing is an unpredictable event and fish are highly perishable, migratory in nature and sensitive to climatic change impacts. Other socioeconomic factors like poor and obsolete fishing gears and postharvest equipment and low financial capital reduces the adaptive capacity of fisherfolks in the two lakes. Results show that the multidisciplinary approach combining quantitative and qualitative information from different sources provide pertinent insights into the impacts of climate change, land use patterns, catchment dynamics and other socioeconomic factors on water and fisheries resources and livelihood of fisherfolks in peri-urban lakes. There is a need for an integrated approach in order to enhance future national capture fisheries plans and action programmes and stimulating conservation of climate sensitive freshwater resources in peri-urban Lakes Chivero and Manyame in Zimbabwe