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Supplementary tables and figures

Supplementary Figures Tables

Historical thematic maps and remote sensing data were applied to address spatiotemporal dynamics of land use/land cover (LULC) changes and its impact on wetlands sustainability based on eight LULC datasets from 1954 to 2015 in Baoqing County, Northeast China. This study demonstrated that LULC drastically changed in the past six decades due to conversion of wetlands, woodland, and grassland into cropland. The cropland was 578.8 km2 in 1954, accounting for 5.8% of the area in Baoqing County, and it increased to 54.3% in 2015, which was nearly equivalent to 9.4 times of that in 1954. Cropland increased 4843.6 km2 from 1954 to 2015 with average increased area of 79.4 km2/yr. The conversion of wetlands was the main reason for cropland increase (49.7%), and woodland (18%) and grassland (16.3%) conversion were other reasons. Results also revealed that 78% of wetlands were lost during the past six decades, of which 91.2% were converted cropland. Population increasing (population across Baoqing in 2015 was 7.8 times of that in 1949), agricultural technology development was the main reason for cropland increase, institutional and economic policies also played important roles for cropland dynamics, particularly paddy field influenced by market price. Agricultural development has caused severe wetlands degradation both in area and functionality, and still being the major threads for wetlands sustainable development. Several suggestions concerning the future land use policy formulation and wetlands sustainability were proposed. They are adjusting the ‘food first’ agricultural policy, reinforce management for wetlands nature reserves, creating infrastructure for the rational use of surface and groundwater, harnessing the degraded cultivated land.

The dynamics of snow cover differs greatly from basin to basin in the Songhua River of Northeast China, which is attributable to the differences in the topographic shift as well as changes in the vegetation and climate since the hydrological year (HY) 2003. Daily and flexible multi-day combinations from the HY 2003 to 2014 were produced using Moderate Resolution Imaging Spectroradiometer (MODIS) from Terra and Aqua remote sensing satellites for the snow cover products in the three basins including the Nenjiang River Basin (NJ), Downstream Songhua River Basin (SD) and Upstream Songhua River Basin (SU). Snow cover duration (SCD) was derived from flexible multiday combination each year. The results showed that SCD was significantly associated with elevation, and higher SCD values were found out in the mountainous areas. Further, the average SCDs of NJ, SU and SD basins were 69.43, 98.14 and 88.84 d with an annual growth of 1.36, 2.04 and 2.71 d, respectively. Binary decision tree was used to analyze the nonlinear relationships between SCD and six impact factors, which were successfully applied to simulate the spatial distribution of depth and water equivalent of snow. The impact factors included three topographic factors (elevation, aspect and slope), two climatic factors (precipitation and air temperature) and one vegetation index (Normalized Difference Vegetation Index, NDVI). By treating yearly SCD values as dependent variables and six climatic factors as independent variables, six binary decision trees were built through the combination classification and regression tree (CART) with and without the consideration of climate effect. The results from the model show that elevation, precipitation and air temperature are the three most influential factors, among which air temperature is the most important and ranks first in two of the three studied basins. It is suggested that SCD in the mountainous areas might be more sensitive to climate warming, since precipitation and air temperature are the major factors controlling the persistence of snow cover in the mountainous areas.

Aquaculture ponds are one of the fastest-growing land use types in valuable and fertile coastal areas and have caused serious environmental problems. Quantitative assessment of the extent, spatial distribution, and dynamics of aquaculture ponds is of utmost importance for sustainable economic development and scientific management of land and water resources in the coastal area. An object- oriented classification approach was applied to Landsat images acquired over three decades to investigate the long-term change of aquaculture ponds in the coastal region of the Yellow River Delta. The results indicated that the aquaculture ponds in the study area undergone a sharp expansion from 40.38 km2 in 1983 to 1406.89 km2 in 2015, and the fast expansion occurred during the period of 2010–2015 and 1990–2000. Natural wetlands, especially mudflat, and cropland were main land use types contributing to the increase of aquaculture ponds. The patches of aquaculture ponds were consequently prevalence in the north of the Yellow River Estuary and landscape metrics indicated an increase of the aquaculture ponds of the study area in the quantity and complexity. The expansion of aquaculture ponds inevitably had negative effects on the coastal environment, including loss of natural wetlands, water pollution and land subsidence, etc. The results from this study provide baseline data and valuable information for efficiently planning and managing aquaculture practices and for effectively implementing adequate regulations and protection measures.

Reclamation is one of the fastest-growing land use type developed in coastal areas and has caused degradation and loss of coastal wetlands as well as serious environmental problems. This paper was aimed at monitoring the spatiotemporal patterns of coastal wetlands and reclamation in the Yangtze Estuary during the 1960s and 2015. Satellite images obtained from 1980 to 2015 and topography maps of the 1960s were employed to extract changes of reclamation and coastal wetlands. Area-weight centroids were calculated to identify the movement trend of reclamation and coastal wetlands. The results show that from the 1960s to 2015, the net area of natural wetlands declined by 574.3 km2, while man-made wetlands and reclamation increased by 553.6 and 543.9 km2, respectively. During the five study phases, the fastest areal change rate natural wetlands was–13.3 km2/yr in the period of 1990–2000, and that of man-made areas was 24.7 km2/yr in the same period, and the areal change rate of reclamation was 27.6 km2/yr in the period of 2000–2010. Conversion of coastal wetlands mainly occurred in the Chongming Island, Changshu City and the east coast of Shanghai Municipality. Reclamation was common across coastal areas, and was mainly attributed to settlement and man-made wetlands in the Chongming Island, Lianyungang City and the east coast of Shanghai Municipality. Natural wetlands turned into farmlands and settlement, and man-made wetlands gained from reclamation of farmlands. The centroid of natural wetlands generally moved towards the sea, man-made wetlands expanded equally in all directions and inland, and the centroid of reclamation migrated toward Shanghai Municipality. Sea level rise, erosion-deposition changes, and reclamation activities together determine the dynamics of the Yangtze Estuary wetlands. However, reclamation activities for construction of ports, industries and aquaculture are the key causes for the dynamics. The results from this study on the dynamics of coastal wetlands and reclamation are valuable for local government to put forward sustainable land use and land development plans.