Salinity is a major driver of emergence and early growth of mangrove propagules. The magnitude of salinity effects may vary across mangrove ecotypes. Using a randomised complete block design in a semi‐controlled experiment, this study assessed the effect of salinity (low: 3–5, moderate: 15–17 and high: 34–36 Practical Salinity Unit) on the emergence and early growth of Rhizophora racemosa (G.) Meyer and Avicennia germinans (L.) L., two common mangrove species in West Africa. Per cent emergence, total height and number of leaves were recorded daily for 30 days. Data were analysed using a three‐parameter log‐logistic distribution and linear mixed models. For both species, results showed significant effects of salinity on per cent emergence and growth variables. There was a negative correlation between salinity and per cent emergence of A. germinans and between salinity and height and number of leaves during the early growth phase of both species. However, the per cent emergence of R. racemosa was significantly higher for moderate salinity. To avoid the risk of dieback from osmotic shock after transplantation, we recommend the use of water of low or moderate salinity in nursery, depending on whether the soil salinity is low or high where the seedlings will be transplanted.

Mangroves are precious ecosystems that provide vital socio-economic, environmental and cultural benefits to humanity. However, they are declining alarmingly due to human activities and natural hazards. Assessment of their spatio-temporal dynamics is essential to monitor these ecosystems and guide their management to ensure sustainability. We assessed the spatio-temporal dynamics of mangroves and predicted their future trends using remote sensing techniques and Markovian chain analysis. Landsat images TM/ETM+ (for 1988, 2001 and 2019) were obtained, processed, classified and analyzed using remote sensing techniques and GIS. The changes observed during these periods (1988–2001, 2001-2019 and 1988–2019) were used to predict future trends up to 2050, using Markovian chain analysis. The results showed that the mangrove area studied, which occupied 5205.24 ha in 1988, declined by 62.07% between 1988 and 2001 but increased by 18.84% from 2001 to 2019. This increase is attributed to strengthened mangrove restoration efforts. The mangroves had mainly been converted into grassland (52.35% in 1988-2001 and 7.31% in 2001-2019) and other vegetation types (17.57% in 1988-2001 and 27.05% in 2001-2019). Their decline was most severe in the municipalities of Abomey-Calavi and Ouidah, which therefore require greater conservation efforts. Our projection based on Markovian chain analysis suggests that these mangroves will continue to decline, but slowly. This study provides essential information to guide future mangrove conservation action in the study area.