High vulnerability of coastal wetlands in Chile at multiple scales derived from climate change, urbanization, and exotic forest plantations

Biodiversity Dynamics in a Ramsar Wetland: Assessing How Climate and Hydrology Shape the Distribution of Dominant Native and Alien Macrophytes

Coastal wetlands provide critical ecological services but are threatened by the human, climatic, and hydrological changes impacting these ecosystems. Several key ecosystem services and functions rely on aquatic macrophyte plant species. We integrate 10 years of seasonal monitoring data (2014-2024) and climatic and hydrological datasets to assess how environmental variability influences two dominant aquatic macrophytes-the invasive and non-indigenous Elodea densa Planch. Casp. (Hydrocharitaceae) and the native Schoenoplectus californicus (C.A.Mey.) Soják-in Chile's first Ramsar site, Carlos Anwandter, and a Nature Sanctuary. We modeled suitable habitat areas using MaxEnt software with Landsat 8 spectral bands and indices as predictive layers. We found significant recent decreases in temperature, river flow, and water level, with a nonsignificant shift in precipitation. We also observed marked spatial and temporal fluctuations in areas with suitable habitat areas for both macrophytes. Stepwise regression analyses indicated that Elodea densa expanded with increasing temperature over time but declined with water level variability. Schoenoplectus californicus showed contrasting effects, declining with rising temperature and water levels but expanding with higher precipitation. These findings emphasize the complexity of coastal wetland ecosystems under environmental stress and climate change and the need for further research for the conservation and management of coastal wetlands along migratory flyways such as the Southeastern Pacific Flyway.

Assessing the impacts of reclamation and invasion on ecological dynamics of coastal wetland vegetation in the Yangtze Estuary from 1985 to 2019:A case study of Chongming Island, China

The distribution of coastal wetland vegetation is influenced by biological invasions, human reclamations and climate changes, which continually reshape vegetation structures. However, limited attention has been given to the impact of biological invasion on native vegetation and tidal wetlands. This study focuses on the wetlands of Chongming Island, employing a multi-feature dataset combining spectral, phenological, and temporal information on the Google Earth Engine (GEE) platform. Using the Random Forest (RF) classification method, we analyzed annual vegetation distribution changes and examined the distinct effects of natural and anthropogenic factors. The research results indicate that: (1) From 1985 to 2019, the total area of Chongming Island expanded, while wetland vegetation decreased due to embankment construction and island connection projects. (2) The total area of wetland vegetation on Chongming Island dropped to its lowest point in 2002 (3812.76 ha), and then gradually recovered. (3) Human reclamation was the primary driver of vegetation changes from 1985 to 1995. (4) Vegetation distribution in Dongtan was influenced by both human and natural factors, whereas Beiliuyao affected by the invasion and expansion of the S. alterniflor. These findings provide valuable insights into the drivers of long-term vegetation distribution changes, offering essential data and theoretical support for sustainable development and management of Chongming Island's ecosystems.

Chilean Mediterranean forest on the verge of collapse? Evidence from a comprehensive risk analysis

World forests are experiencing significant modification due to the confluence of climate change and deforestation, with Mediterranean forests facing particularly acute threats. The Chilean Sclerophyllous Mediterranean Forest is considered a world biodiversity hotspot, a restricted ecosystem type that is highly affected by global change drivers. Despite the high ecological and environmental importance of this ecosystem, an integrated assessment of its risk derived from climate and land-use change is lacking. This study estimates the level of risk of all sclerophyll forest stands in Chile, by assessing their exposure to several factors linked with climate change, land cover change, wildfires, change in the vegetation functional properties, and habitat fragmentation. We also generated a spatially explicit estimate of the main factors underlying the risk of each sclerophyllous forest stand. We constructed a multifactorial risk index based on the different analyzed variables, exploring the main drivers associated with the risk of each forest stand using principal components analysis with agglomerative hierarchical clustering. We found that 39.8 % of sclerophyll forest stands reached a high or very high-risk index, with the highest levels concentrated between 32°S and 34°S. The vigor and net primary production of sclerophyll forest stands decreased in 90.9 % and 86.6 %, respectively. We identified three groups of forest stands: A) northern group (29.9°S to 33.5°S), which has experienced high decrease of net primary production and vegetation vigor; B) central group (32°S to 35°S), also affected by degradation and replacement by croplands; and C) southern group (34°S to 39°S), affected by drought and exotic forest plantations. The results of this study provided clarity on the current state of the sclerophyll forest, allowing for the identification of spatial differences in the risk and their underlying factors. Our results and data can be useful for informing policy and supporting sustainable management of government agencies and practitioners.

Mapping of water spread dynamics of a tropical Ramsar wetland of India for conservation and management

Wetlands are dynamic ecosystems vital for sustaining ecological health and development at regional and global scales. Geospatial tools have emerged as essential for managing wetland ecosystems. This study assessed the spatiotemporal dynamics of water spread in the Point Calimere Wetland, a coastal Ramsar site located along the Bay of Bengal, India, from 1984 to 2023. The analysis based on Global Surface Water Explorer (GSWE) and Normalized Difference Water Index (NDWI) derived from Landsat 5, 7, and 8 data revealed that 21% of the total wetland area showed an increasing trend. In comparison, 5.7% of the area showed a decreasing trend of surface water coverage, largely driven by erosion and climatic variability. The mean water spread increased from 119.47 km2 (2000-2003) to 160.88 km2 (2020-2023), with notable seasonal fluctuations. Among all seasons, the monsoon with the highest surge (41.1%) in water dynamics reported the largest water spread in 2020-2023 (221.87 km2). A moderate positive and negative relationship was noted between rainfall and water spread (r = 0.35) and temperature and water spread (r = - 0.43). A marked increase in habitat patches and edge density between 2000-2003 and 2020-2023 indicates the wetland's vulnerability to changing climatic conditions and the critical role of seawater intrusion, shoreline changes, and tidal forces in shaping its hydrological dynamics. The data presented on the historical water dynamics in this study is invaluable for the conservation planning and management of wetlands to support the associated coastal biodiversity and livelihood of the dependent communities.

Spatiotemporal lake area changes influenced by climate change over 40 years in the Korean Peninsula

Water resources in lakes of the Korean Peninsula play a significant role in society and ecosystems in both South and North Korea. This study characterized spatiotemporal changes in the lake area during the dry season (March-May) in the Korean Peninsula over the last 40 years. The satellite images (Landsat 5-9) were used to derive annual areas of 975 lakes during the dry season from 1984 to 2023. Our analysis indicated that the MNDWI is the optimal remote sensing-based index for delineating lake areas in the Korean Peninsula, with an overall accuracy of 92.3%. Based on the selected index, the total lake areas of the dry seasons have increased from 1070.7 km2 in 1984 to 1659.3 km2 in 2023, mainly due to newly constructed dam reservoirs. While the detailed changes in lake area vary, we found divergent results based on their sizes. The large lakes (> 10 km2) showed their area increased by 0.0473 km2 (0.1%) every year and have more influences from climate change. On the contrary, the small lakes (≤ 10 km2) have area decreases by 0.0006-0.006 km2 (0.15-0.5%) every year and have less influence from climate change. This study shows that the spatiotemporal lake area changes are determined by either climate change or human activity.