Despite the importance of coastal ecosystems for the global carbon budgets, knowledge of their carbon storage capacity and the factors driving variability in storage capacity is still limited. Here we provide an estimate on the magnitude and variability of carbon stocks within a widely distributed marine foundation species throughout its distribution area in temperate Northern Hemisphere. We sampled 54 eelgrass (Zostera marina) meadows, spread across eight ocean margins and 36° of latitude, to determine abiotic and biotic factors influencing organic carbon (C_org) stocks in Zostera marina sediments. The C_org stocks (integrated over 25‐cm depth) showed a large variability and ranged from 318 to 26,523 g C/m² with an average of 2,721 g C/m². The projected C_org stocks obtained by extrapolating over the top 1 m of sediment ranged between 23.1 and 351.7 Mg C/ha, which is in line with estimates for other seagrasses and other blue carbon ecosystems. Most of the variation in C_org stocks was explained by five environmental variables (sediment mud content, dry density and degree of sorting, and salinity and water depth), while plant attributes such as biomass and shoot density were less important to C_org stocks. Carbon isotopic signatures indicated that at most sites <50% of the sediment carbon is derived from seagrass, which is lower than reported previously for seagrass meadows. The high spatial carbon storage variability urges caution in extrapolating carbon storage capacity between geographical areas as well as within and between seagrass species.

Understanding how local communities perceive and depend on mangrove ecosystem services (MES) is important for translating and incorporating their benefits, priorities, and preferences into conservation and decision-making processes. We used focus group discussions, key informant interviews, household questionnaires, and direct observations to explore how local communities in the Rufiji Delta perceive a multitude of MES and factors influencing their perceptions. Sixteen MES were identified by the respondents. Provisioning services were the most highly identified services, accounting for 67% of the overall responses, followed by regulating (53%), cultural (45%), and supporting (45%) services. Poles for building, firewood for cooking, coastal protection, and habitats for fisheries were perceived as the most important MES to sustain local livelihoods, although the perceptions differed between sites. Distance from household homes to mangroves and residence time were significant predictors of the local communities’ awareness of all identified MES. Gender of household heads and performance of local management committees also determined the local communities’ awareness of provisioning, regulating, and cultural services. We conclude that perceptions of MES are context-specific and influenced by multiple factors. We believe a deeper understanding of local stakeholders’ preferences for MES can help strengthen the link between local communities and conservation actors and can provide a basis for sustainable management of mangrove forests.

Mangroves are increasingly recognized for their role in supporting adaptation to climate change and variability. However, knowledge about how climate change and variability affect mangrove ecosystem services (MES) and their role in supporting coastal communities to adaption is limited in Tanzania. We used participatory rural appraisal methods and field observations to explore local communities' perceptions of climate change and variability, and ecosystem-based adaptation (EbA) strategies in the mangroves of the Rufiji Delta, Tanzania. Decrease in rainfall, increased temperatures, coastal flooding, and the incidence of sea level rise were identified as key variables associated with a changing climate in the delta. Perceived climatic stresses included damaged fish breeding sites, altered climate regulation and a decrease in coastal protection and flood control. Decline in crop, fish and honey production were perceived as the main impacts on community livelihoods, although there were significant differences across occupational groups. Dependence on MES in times of shocks, such as when agriculture production fails, switching of occupation, crop diversification, fishing in deep waters and migration to other areas provided potential adaptation options. Although the reported perceptions related to climate change or variability are not explicit, they both have negative consequences to mangrove dependent communities' livelihoods.