Diversity of benthic macrofauna and physical parameters of sediments in natural mangroves and in afforested mangroves three decades after compensatory planting

Abstract

Mangroves in the Arabian Gulf are under pressure from land use change, leading to compensatory planting at sites without natural mangroves. In this study, we examine the potential long-term success of this form of afforestation of mangroves as a conservation measure supporting biodiversity. We compared the community of benthic macrofauna (in total 13,522 individuals from 75 species) and physical parameters at 15 sampling points in five afforested mangrove communities and 19 stations in four natural mangrove communities in Qatar. Three decades after afforestation, there were no significant differences between the benthic macrofauna in natural and afforested mangroves as regards total abundance, species richness, Shannon’s diversity, effective number of species, or evenness. Only species richness of Crustacea was significantly higher in natural mangroves. Total organic carbon (TOC), sand, and clay content did not differ. This contradicts findings at the same locations 10 years after afforestation, when benthic macrofauna diversity, TOC, and clay content were lower at afforested sites than at natural mangrove sites. Our results suggest that compensatory planting of mangroves in areas without previous natural occurrence can potentially compensate for loss of biodiversity due to coastal development and that physical parameters may become more similar in afforested mangroves and natural mangroves over time. Furthermore, the increase in TOC in sediments in afforested mangroves over time can help mitigation of climate change. Importantly, the results highlight the need for long-term studies and perspectives when evaluating conservation practices.