Expansion of Exotic Mangroves Sonneratia apetala in China Since Start of the SDGs

Since the Sustainable Development Goals (SDGs) came into effect in 2016, mangroves have received unprecedented attention for carbon sequestration capacity. In China, previous studies focused on the total area of mangroves using remote sensing technique, neglecting expansion of the exotic mangrove species Sonneratia apetala , even when it is encroaching on habitat of native species. We proposed a robust and interpretable approach to identify the exotic species, applied this approach to generate S. apetala map in China for 2024 using Sentinel‐1/2 imagery, and revealed its expansion since start of the SDGs by combining existing data sets. The approach, in the form of a decision rule—Sentinel‐1 VH (vertical transmit–horizontal receive polarization) ≥ −14.390 & Sentinel‐2 B11 (shortwave infrared band) < 0.084—achieved an overall accuracy of 97.0% for the S. apetala map. The total area of the exotic species in China for 2024 was 3675 ha, which is ∼1.25 times the area in 2020 and ∼1.99 times that in 2016. The expansion characteristics of the species were analyzed from multiple perspectives, including at the provincial level, inside and outside national mangrove nature reserves (NMNRs), and across NMNRs. Hotspots of expanded S. apetala were also identified, revealing that these regions are in varied expansion stages. We also reported area and expansion‐rate estimates with uncertainties. This study reveals whether a pixel from Sentinel‐1/2 imagery is inferred as S. apetala . This study provides the first holistic view on expansion dynamics of exotic species, alongside the shrinking habitats of native species.