Remote Observation in Habitat Suitability Changes for Waterbirds in the West Songnen Plain, China

Deteriorating wintertime habitat conditions for waterfowls in Caizi Lake, China: Drivers and adaptive measures

China has made enormous strides to achieve high-quality development and biodiversity conservation, and the establishment of nature-protected areas is one of the essential initiatives. Caizi Lake involves a natural reserve and two national wetland parks, accommodating winter migratory waterfowl over the middle and lower Yangtze River basin in China. However, the water transfer from the Yangtze River to the Huai River (YR-HR water transfer) has modified the winter hydrological conditions of Caizi Lake, negatively affecting wintertime waterfowl habitats. Hence, conserving wintertime waterfowl habitats necessitates knowledge of the dynamical mechanisms behind the impacts of YR-HR water transfer on wintertime waterfowl habitats and adaptive measures. Here we developed a machine learning model, the normalized difference vegetation index, and on-spot observatory datasets such as the spatial distribution of waterfowl species and underwater topography of Caizi Lake. We found that the rising winter water level of Caizi Lake encroaches on winter waterfowl habitat with extremely high suitability. Meanwhile, rising water levels reduced waterfowl food sources. Thus, rising water levels due to YR-HR water transfer deteriorated waterfowl living conditions over Caizi Lake. Therefore, we proposed adaptive measures to alleviate these negative effects, such as water level regulation, artificial feeding of waterfowls, restoration and reconstruction of contiguous mudflats, grass flats. This study highlights human interferences with waterfowl habitats, necessitating biodiversity conservation at regional scales.

Response of vegetation variation to climate change and human activities in semi-arid swamps

Vegetation is a sensitive factor in marsh ecosystems, which can provide nesting sites, foraging areas, and hiding places for waterfowl and can affect their survival environment. The Jilin Momoge National Nature Reserve, which consists of large areas of marshes, is located in the semi-arid region of northeast China and is an important stopover site for the critically endangered species of the Siberian Crane (Grus leucogeranus). Global climate change, extreme droughts and floods, and large differences in evaporation and precipitation in this region can cause rapid vegetation succession. In recent years, increased grain production and river-lake connectivity projects carried out in this area to increase grain outputs and restore wetlands have caused significant changes in the hydrological and landscape patterns. Therefore, research on the response of variation trends in vegetation patterns to the main driving factors (climate change and human activities) is critical for the conservation of the Siberian Crane. Based on the Google Earth Engine (GEE) platform, we obtained and processed the Normalized difference vegetation index (NDVI) data of the study area during the peak summer vegetation period for each year from 1984 to 2020, estimated the annual vegetation cover using Maximum value composites (MVC) method and the image dichotomy method, calculated and analyzed the spatial and temporal trends of vegetation cover, explored the response of vegetation cover change in terms of climate change and human activities, and quantified the relative contribution of both. The results revealed that first, from the spatial and temporal changes, the average annual growth rate of regional vegetation was 0.002/a, and 71.14% of the study area was improved. The vegetation cover showed a trend of degradation and then recovery, in which the percentage of high vegetation cover area decreased from 51.22% (1984-2000) to 28.33% (2001-2005), and then recovered to 55.69% (2006-2020). Second, among climate change factors, precipitation was more correlated with the growth of vegetation in the study area than temperature, and the increase in precipitation during the growing season could promote the growth of marsh vegetation in the Momoge Reserve. Third, overall, human activities have contributed to the improvement of vegetation cover in the study area with the implementation of important ecological projects, such as the return of farmland to wetlands, the return of grazing to grass, and the connection of rivers and lakes. Fourth, climate change and human activities jointly drive vegetation change, but the contribution of human activities in both vegetation improvement and degradation areas (85.68% and 78.29%, respectively) is higher than that of climate change (14.32% and 21.71%, respectively), which is the main reason for vegetation improvement or degradation in the study area. The analysis of vegetation pattern change within an intensive time series in semi-arid regions can provide a reference and basis for studying the driving factors in regions with rapid changes in vegetation and hydrological conditions.

Potential Habitats and Their Conservation Status for Swan Geese (Anser cygnoides) along the East Asian Flyway

Habitats provide essential space for migratory birds to survive and reproduce. Identifying potential habitats in annual cycle stages and their influencing factors is indispensable for conservation along the flyway. In this study, we obtained satellite tracking of eight swan geese (Anser cygnoides) wintering at Poyang Lake (28°57′4.2″, 116°21′53.36″) from 2019 to 2020. Using the Maximum Entropy species distribution model, we investigated the potential habitats distribution of the swan geese during their migration cycle. We analyzed the relative contribution of various environmental factors to habitat suitability and conservation status for each potential habitat along the flyway. Our results show that the primary wintering grounds of swan geese are located in the middle and lower reaches of the Yangtze River. Stopover sites were widely distributed, mainly in the Bohai Rim, the middle reaches of the Yellow River, and the Northeast Plain, and extended westward to Inner Mongolia and Mongolia. Breeding grounds are mainly in Inner Mongolia and eastern Mongolia, while some are scattered in Mongolia’s central and western. The contribution rates of major environmental factors are different in breeding grounds, stopover sites, and wintering grounds. Breeding grounds were influenced by slope, elevation, and temperature. Slope, human footprint index, and temperature were the main factors that affected stopover sites. Wintering grounds were determined by land use, elevation, and precipitation. The conservation status of habitats is 9.6% for breeding grounds, 9.2% for wintering grounds, and 5.3% for stopover sites. Our findings thus provide a critically international assessment of potential habitats protection for geese species on the East Asian Flyway.

Tracking Historical Wetland Changes in the China Side of the Amur River Basin Based on Landsat Imagery and Training Samples Migration

In the recent decades, development of agricultural and human settlements have severely affected wetlands on the China-side of the Amur River Basin (CARB). A long-term holistic view of spatio-temporal variations of the wetlands on the CARB is essential for supporting sustainable conservation of wetlands in this region. In this study, a training sample migration method along with Random Forest classifier were adopted to map wetland and other land covers from two key seasons image collections. The proposed classification method was applied to Landsat images, and a 30-m resolution dataset was obtained, which reflected the dynamic changes of historical wetland distribution on the CARB region from 1990 to 2010. As the accuracy assessments showed, land cover maps of the CARB had high accuracies. The classification results indicated that the wetland area decreased from 89,432 km2 to 75,061 km2 between 1990 and 2010, with a net loss of 16%, which was mainly converted to paddy field and dry farmland, and the changes were most obvious in Sanjiang Plain and Songnen Plain. This suggests that agricultural activities are the main cause of wetland loss. The results can provide reliable information for the research on wetland management and sustainable development of the society and economy in the CARB.

Optimization of the Weighted Linear Combination Method for Agricultural Land Suitability Evaluation Considering Current Land Use and Regional Differences

This study was aimed at optimizing the weighted linear combination method (WLC) for agricultural land suitability evaluation (ALSE) through indicator selection, weight determination, and classification of overall suitability scores in Handan, China. Handan is a representative research area with distinct agricultural advantages and regional differences in land use, where the expansion of construction land has led to a rapid decrease of agricultural land in recent years. Natural factors (topography, climate, soil conditions, and vegetation cover) and socioeconomic factors (land use and spatial accessibility) were selected to establish a more comprehensive evaluation system. The index weight was calculated by the mutual information between index suitability and current land use. The consistency index was used to identify the boundary value dividing the overall suitability score into a suitable category and unsuitable category in each sub-region. The results demonstrated that the optimized WLC-ALSE model outperformed the comparison models using conventional methods in terms of the consistency between the evaluation results and current land use. Owing to the increasing limitations of topography, soil conditions, spatial accessibility, and land use, the proportions of suitable land in Zone 1, Zone 2, and Zone 3 were 77.4%, 67.5%, and 30.9%, respectively. The agricultural land unsuitable for agriculture (14.5%) was less than non-agricultural land suitable for agriculture (7.4%), indicating that agricultural land had low growth potential in Handan. Finally, specific recommendations were made to improve agricultural land suitability, alleviate land use conflicts, and further optimize the model. The results can provide effective guidance for WLC-ALSE and land use decision-making for sustainable agriculture.

Assessment of Ecological Carrying Capacity and Ecological Security in China’s Typical Eco-Engineering Areas

The implementation of ecological restoration programs is intensively changing the original ecological carrying capacity and the status of ecological security. To evaluate the spatiotemporal variation of ecological carrying capacity and ecological security in China’s eco-engineering areas, an indicator system of ecological carrying capacity and ecological security should be developed. This study developed an evaluation indicator system that contains 29 indicators. The indicators were generated by long-time series and multi-source data. The indicator system presents the relationship between ecological carrying capacity and ecological security and reflects the dynamic change of them in eco-engineering areas. We selected the Three-River Headwaters Region (TRHR) and implemented the Ecological Conservation and Construction Program (ECCP) as a case study. The results showed the variation of ecological carrying capacity (ECC) and ecological security (ES) in the TRHR before (2000–2004), during early term (2005–2009), and during medium term (2010–2015) implementation of ECCP, and limiting factors of ecological carrying capacity and ecological security in TRHR was analyzed. The results showed that the ECC index and the ES index were significantly increase, indicating that the ECC improved and that the ES state got better in the TRHR after implementing ECCP. The water conservation was the major factors limiting the increase of the ECC. The leading factors limiting the improvement of the ES were educational expenditure before 2010 and turned into proportion of tertiary industry and investments for ecological restoration after 2010. The implementation of the ECCP has improved the ES state but has also resulted in new problems. It provides a scientific reference for future research on the indicator system of ecological carrying capacity and ecological security in eco-engineering areas and also has vital practical significance to guide the sustainable development of ecological restoration programs.