Understanding the complexity and dynamics of mangrove social-ecological systems through the use of a resilience approach in Unguja, Zanzibar
There has been growing concern by policy and other decision makers that timber extraction by local communities is the main threat to achieving sustainable management of mangrove systems in Unguja Island, Zanzibar, Tanzania. However, this concern, and responses to the perceived threat to date, do not appear to be informed by a clear understanding of the complexity and capacity of mangrove Social-Ecological Systems (SES) at different scales to adapt to this and other disturbances. The aim of this study was to assess the resilience of mangroves to the increased demand for provisioning ecosystem services and other drivers with a view to identifying options for sustainable mangrove management on Unguja Island. This study was guided by broad resilience concepts and specific approaches, particularly the components-relationship-innovation-continuity framework developed by Cumming et al. (2005). Data relating to both social and ecological components of the mangrove system was collected. A total of 185 plots were surveyed within mangrove forests from three case study sites of Pete- Jozani, Charawe and Michamvi Shehia (lowest administrative unit) on Unguja Island in which mangrove tree species, diameter and height of trees, the numbers of seedlings and stumps were collected to assess the ecological condition of the forests. Key informant interviews (with government officials and village stakeholders), semi-structured household interviews, village meetings and focus group discussions (with beekeepers, mangrove harvesters, village elders and village conservation organisations) were used to collect social-economic data from the three case study sites. The results showed that between the 1920s and 1970s at each case study site local communities reported that they were able to obtain diverse ecosystem services while the key variables that defined the identities of the mangrove SES were maintained. The mangrove SES from each case study site was found to have changed over the past three decades in temporal and spatial scales and currently reside at different phases of change. The current mangrove ecological systems of Pete, Charawe and Kinani (part of Michamvi) were found to have been degraded compared to the past. This was evidenced by the quality and quantity of trees present, with a relatively high density of small-sized mature trees with correspondingly small basal areas and volumes, together with significant numbers of tree stumps in the ecosystems. The areas covered by mangrove vegetation in the study sites were also found to have declined. The decline in quality and quantity of trees was found to correspond with a reduction in desirable ecosystem services as reported by communities. The levels of dependence on mangrove wood provisioning ecosystem services and management approaches have changed across the case study sites. Excessive rates of harvesting of mangrove wood were identified as the key direct driver on mangrove ecological systems, which was fuelled by several underlying drivers including poverty, population change, limited livelihood activities, inappropriate management regimes, and markets for trading mangrove wood ecosystem services. Vijichuni mangrove (another part of Michamvi) was found to be an exceptional case whereby the quality and quantity of mangrove ecological variables had improved. Availability of reliable alternative income sources by the majority of villagers and effective management institutions had contributed to these changes. The drivers identified were used to develop three alternative future scenarios to explore whether projected changes will result in the mangrove SES maintaining their identities in the future. The findings suggest that the Non-inclusive State Control scenario strictly conserves the mangroves, but does not provide alternative livelihood opportunities to improve the well-being of local communities and so is not desirable. Coastal Boom scenario, characterised by unregulated economic growth, particularly in the tourism sector and community forest management with limited benefits for local communities, results in complete degradation of mangrove and reduced wellbeing of local people. However, the Techno-green scenario which includes green growth, access to low-cost cooking energy and co-managed mangrove forests with benefits for local communities, provides decision makers and other stakeholders with an alternative pathway towards more resilient mangrove SES in Unguja.
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