Ensemble habitat suitability model predicts Suaeda salsa distribution and resilience to extreme climate events.

Abstract

Climate anomalies lead to an increased occurrence of extreme temperature and drought events in coastal wetlands, resulting in heightened survival pressure on salt marsh plants. It is imperative to anticipate the effects of these events on the habitat suitability and resilience of coastal salt marsh vegetation to inform restoration efforts and management strategies. Herein, an ensemble model was developed to evaluate the recovery of Suaeda Salsa in the two subsequent years following the anomalously high temperatures and decreased precipitation experienced during the summer of 2018, potentially leading to a decline in this species in the eastern coast of Liaohe Estuary wetland (Bohai Sea, China). Additionally, the resilience of the ecosystem was evaluated based on the evolution of density and morphology metrics of S. salsa. The findings suggest that the ensemble model demonstrates exceptional predictive performance in assessing habitat suitability, as evidenced by True Skill Statistic (TSS) values of 0.94 ± 0.02 and 0.96 ± 0.03 for the years 2019 and 2020, respectively, and Area Under the Receiver Operating Characteristic Curve (AUC) values of 0.96 ± 0.03 in 2019 and 0.97 ± 0.02 in 2020. Tidal elevation and soil salinity were identified as the primary predictors for the habitat suitability of S. salsa, while sand content emerged as the most influential factor driving its expansion. The core and suitable habitat areas of S. salsa experienced a significant increase from 9.61 ± 1.16 km² in 2019 to 15.66 ± 2.24 km² in 2020, representing a 62.96 ± 8.44 % growth. A notable increase in density and above-ground biomass was noted, indicating a potential recovery of salt marsh vegetation from multi-stresses. However, a decline in below-ground biomass, from 61.9 g m^-2 in August 2018 to 39.8 g m^-2 in August 2020, suggests a reduction in the resilience of S. salsa to future disturbances. This decrease in below-ground reserves, which were crucial for the tolerance of S. Salsa, may impact the vegetation's ability to withstand future challenges. The results highlight the effectiveness of optimizing freshwater irrigation and implementing artificially constructed tidal channels as strategies for future restoration efforts. Besides, the evaluation method of habitat suitability and bio-metrics proposed herein is applicable to the restoration and protection for other estuarine halophytes.