Sonadia Island is an ecologically important barrier island on the southeastern coast of Bangladesh, where shoreline erosion, saline intrusion, cyclone exposure, and habitat degradation threaten both biodiversity and local livelihoods. This exploratory mixed-methods study assessed community perceptions of existing Jhaw plantations, documented selected dune and vegetation characteristics, and developed a site-specific conceptual bioshield for pilot testing. Fieldwork included measurements of lateral trunk deviation in 20 Jhaw trees, measurements of local dune height at 33 points in Mokchor and Poschim Para, and observations of Nishinda occurrence. Four focus-group discussions involving 32 residents and three key-informant interviews were analyzed thematically and triangulated with field observations and published ecological evidence. Mean lateral deviation of measured Jhaw trees was 1.53 ± 0.48 m (range, 0.73–2.71 m). Nishinda was recorded at 24 of 33 dune points, and the maximum observed local dune height occurred at a point where Nishinda was present; however, the purposive, cross-sectional design cannot determine whether Nishinda promoted sediment accumulation or preferentially occurred on pre-existing higher or more stable dunes. According to community participants, dense Jhaw stands are associated with the loss of native vegetation, reduced cultivable land, altered sand movement, perceived hotter and less ventilated microclimatic conditions, wildlife conflicts, and increased exposure to saline flooding. These accounts are treated as local ecological knowledge rather than verified biophysical effects. On the basis of complementary species functions, a six-layer seaward-to-landward bioshield is proposed: Sagarlata, Nishinda, Keya, Narikel, Boroi, and selectively retained inland Jhaw. The framework prioritizes native dune-building vegetation, ecological connectivity, and livelihood benefits. A pilot-scale restoration, formal baseline monitoring, taxonomic verification, and replicated comparison with Jhaw-dominated and open-dune sites are required before wider implementation.