Impacts of human activities on the mangrove ecosystems: a case of Bagamoyo district in Tanzania

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University of Dar es Salaam
Mangroves are recognised as ecosystems of ecological and social-economical importance. However, despite their importance, these ecosystems are being threatened by human activities. A study was conducted in Kaole, Mlingotini and Pande villages in Bagamoyo district, Tanzania to determine the impacts of human activities on the mangrove ecosystems. Biophysical assessment, household interviews, focus group discussions (FGDs), key informant interviews (KIIs), secondary data review and remote sensing (RS) were the methods employed for data collection. Results indicated that the Bagamoyo’s mangrove ecosystem is comprised of nine tree species (flora species) among which Avicennia marina had the highest density (377 trees.ha’1). It was also noted that, while Lumnitzera racemosa dominate the landward zone, the Ceriops tagal and Sonneratia alba dominated the mid and seaward zones respectively. Further results indicated that, the mangrove ecosystem also support a variety of fauna species including Perisesarma ortmanni which had the highest density (3,500 species.ha'1) compared to others. Tree cut, holes left after digging fish bait, footpath and farming activities were among the observed indicators of human disturbance in the mangrove forest ecosystem. Interviewed respondents, FGDs and KIIs reported that, pole and timber harvesting, crop cultivation as well as shrimp farming were the most destructive activities to the mangrove ecosystem. The analysis of use value showed that Xylocarpus granatum had the highest use value (10.6) whereas Bruguire gymnorrhiza had the lowest use value (0.5). While Xylocarpus granatum and Avicenia marina were perceived as the most threatened tree species especially due to its utilization intensity, some birds, snakes and fish were the most threatened fauna species due to habitat destruction. The analysis of remote sensing imagery over 13 years (from 1998 and 2011) indicated that cultivated land had the highest relative increase of 18% of the total land base. On the other hand, bush land with scattered cropland had the highest relative decreased by 13% of the total land base. Despite the fact that the mangrove forest showed the lowest relative decrease of 1% of the total land base among other land uses with losses, if the current annual loss of 2.1 ha (2.2%) would continue the mangrove would disappear by the year 2042. Findings of this study highlighted the need to regulate the use of mangrove ecosystem by establishing and enforcing land use plans including land use bylaws. Moreover, introduction of appropriate conservation actions such as establishing village land forest reserves, community woodlots and provision of alternative human activities and opportunities would reduce pressure on mangrove ecosystems and conserve threatened flora and fauna species in the area. The ecological impact of the human activities and land use/cover changes over time should be closely monitored to ensure utilization decisions do not compromise the ecological integrity of the Bagamoyo mangrove.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark ()
Lyimo, G E (2016), Impacts of human activities on the mangrove ecosystems: a case of Bagamoyo district in Tanzania, Master dissertation, University of Dar es Salaam. Dar es Salaam