Dynamic changes in mangroves of the largest delta in northern Beibu Gulf, China: Reasons and causes

•Mangrove forests in the Nanliu River Delta have rapidly expanded seaward, while fluvial sediment supply decrease;•Seaward expansion and vertical accretion of bare tidal flats provide physical space for mangrove forests to colonize;•Human activities have caused sudden decreases and increases in mangroves in the Nanliu River Delta.