Optimizing mangrove afforestation: mollusc biodiversity comparisons
reveal optimal mudflat-mangrove area ratio
Abstract
In recent decades, mangrove wetlands globally have suffered from human
activities and climate change, leading to issues like area reduction,
degraded ecological functions and declining biodiversity. Restoration
efforts, primarily through mangrove afforestation (i.e. mangrove
plantation in mudflats), have been widespread, yet they often overlook
the significance of unvegetated mudflats. In addition, under the
condition that the total area of suitable mudflats is limited, the
problem of what is the threshold of mangrove forest and unvegetated
mudflats to better protect mangrove biodiversity has not been solved.
Therefore, this study conducted a field survey of molluscs in mangrove
wetlands in Hainan Island in China, and explored the relative importance
of mangrove and unvegetated mudflats through taxonomic alpha diversity
and functional diversity. The results showed that: (1) Mollusc abundance
of unvegetated mudflats were notably higher than this of mangrove
forests, and the species richness, functional richness and functional
vulnerability were significantly lower than those of mangrove forests;
(2) The abundance and functional vulnerability of molluscs were mainly
affected by sediment properties (pH, interstitial water salinity, median
diameter, total nitrogen, C/N ratio) , while the species richness and
functional richness of molluscs were primarily influenced by vegetation
structure (plant density); (3) Retaining at least 20% of the
unvegetated mudflat area could well protect the biodiversity of mangrove
wetlands. To our knowledge, our study is the first to propose the
proportion of mangrove forests and unvegetated mudflats on the basis of
benthic biodiversity, providing theoretical support and decision-making
reference for mangrove protection and restoration.