Wetlandscape size thresholds for ecosystem service delivery: Evidence from the Norrström drainage basin, Sweden

Impacts of landscape pattern on plants diversity and richness of 20 restored wetlands in Chaohu Lakeside of China

The recovery of wetland function and biodiversity conservation aroused considerable interest in the past decades. Although many advances have been achieved in revealing disturbing factors on plants diversity, the knowledge of biodiversity manipulation, landscape configuration and ecosystem process in restored wetlands remains incomplete. To address this issue, the landscape of 20 restored wetlands' vegetation was classified into five vegetation formations including: upland plants, wet grassland, emergent plants, floating plants and submerged plants. Meanwhile, the configuration of landscape, plants' function traits and the structure of plants communities of each wetland were analyzed. A total of 142 herbaceous plants were identified from 399 samples of 20 lakeside wetlands. The top five predominant species were Typha orientalis, Alternanthera philoxeroides, Phragmites australis, Echinochloa caudata, and Erigeron canadensis. The highest of diversity index was observed in upland plants with Shannon-Wiener index (H) of 0.92 while higher richness of plants was obtained in wet grassland with species of 88. In dry year, the immigration of upland xerophyte and obligated aquatic species to facultative area increased the biodiversity of the ecotone. Meanwhile, this change may also aggravate the diffusion risk of exotic invasive species Erigeron canadensis. Additionally, the results indicated that number and evenness of landscape outweighed Shannon diversity index (SHDI) of wetlands in shaping the richness and diversity of wetland plants. Whereas, the high value of maximum proportion of landscape (Pmax) have reduced the landscape evenness and species richness. A suggested Pmax of <0.5 was benefit for the stability and biodiversity of restored wetlands.

The relationship between mountain wetland health and water quality: A case study of the upper Hanjiang River Basin, China

This study investigates the degradation process of mountain wetlands in the upper Hanjiang River Basin (HRB) over a 30-year span from 1990 to 2020. In particular, the landscape development intensity (LDI) index was employed to conduct a comprehensive assessment of the wetland health. This was subsequently combined with the spatio-temporal changes of water quality in the basin to explore the potential correlations between the health status of mountain wetlands and the associated watershed water quality. The results show that over the past three decades, wetland ecosystems have shrunk by 18% due to conversion into farmland, grass, construction land and forest land. This was significant between 2010 and 2020, as shown by a land use dynamic index of -1.121% during 2010-2020, which was significantly higher than that in the preceding two decades (0.003%, 0.367%) (p < 0.05). LDI values for individual sub-watersheds across different years ranged from 2.39 to 4.93, demonstrating an increasing trend since 2010. This indicates a heightened level of human interference in mountain wetlands. Although the water quality within the basin generally adhered to the Class II surface water quality standard, total nitrogen (TN) (primarily from farming) was a concern. Areas with relatively more human activity were observed to exhibit increased pollution levels, as demonstrated by a positive correlation between LDI and the concentrations of total phosphorus (TP), ammonium nitrogen (NH4+-N), and chemical oxygen demand (COD) in the basin. The LDI of the mountain wetland exhibited a consistent positive correlation with the water quality comprehensive function, both during the flood (r = 0.77-0.81) and non-flood (r = 0.61-0.70) seasons (p < 0.05). This indicates the significant impact of the wetland landscape structure on the water quality within a 1000 m radius on either side of the river. Special attention should be paid to the management and allocation of wetland landscapes within this 1000 m buffer zone. Furthermore, efforts to control upstream pollutant emission should be strengthened.

Tradeoffs and synergies in wetland multifunctionality: A scaling issue

Wetland area in agricultural landscapes has been heavily reduced to gain land for crop production, but in recent years there is increased societal recognition of the negative consequences from wetland loss on nutrient retention, biodiversity and a range of other benefits to humans. The current trend is therefore to re-establish wetlands, often with an aim to achieve the simultaneous delivery of multiple ecosystem services, i.e., multifunctionality. Here we review the literature on key objectives used to motivate wetland re-establishment in temperate agricultural landscapes (provision of flow regulation, nutrient retention, climate mitigation, biodiversity conservation and cultural ecosystem services), and their relationships to environmental properties, in order to identify potential for tradeoffs and synergies concerning the development of multifunctional wetlands. Through this process, we find that there is a need for a change in scale from a focus on single wetlands to wetlandscapes (multiple neighboring wetlands including their catchments and surrounding landscape features) if multiple societal and environmental goals are to be achieved. Finally, we discuss the key factors to be considered when planning for re-establishment of wetlands that can support achievement of a wide range of objectives at the landscape scale.

Non-linear effects of natural and anthropogenic drivers on ecosystem services: Integrating thresholds into conservation planning

Ecosystem services (ESs) have been widely used for ecological protection and land spatial planning. Natural and anthropogenic drivers exhibit a strong dynamic coupling relationship with ESs. However, current ESs-related research focused on mapping the ESs spatially or investing the trade-offs and synergies relationship between ES, ignoring the nonlinear response of ESs to natural and anthropogenic drivers. Here we aimed to investigate the nonlinear effect of 14 potential drivers (8 natural and 6 anthropogenic) on the total value of six typical ESs (ESV). Taking Beijing-Tianjin-Hebei urban agglomeration (BTH) in China as an example, we established 14 constrain lines and identified critical thresholds through the restricted cubic splines (RCS) regression. We found strong non-linear impacts of natural and anthropogenic drivers on ESV and critical thresholds existed among all the 14 constrain lines. The RCS plots showed that the overall ESV was kept at a high level before or after certain thresholds (e.g., altitude >687 m, slope >13.4°, NDVI >0.7, distance from water <31.2 km, etc.). We categorized these threshold combinations and found the potentially high ES delivery areas were mainly distributed in the Yanshan Mountian, accounting for approximately 5% of the total BTH region. These critical thresholds offer a new method to delineate conservation and restoration priority areas.

Scaling relations reveal global and regional differences in morphometry of reservoirs and natural lakes

Water bodies provide essential ecosystem services linked to morphometric features that might differ between natural lakes and reservoirs. We use the HydroLAKES global dataset to quantitatively compare large (area > 1 km²) reservoirs and natural lakes in terms of scaling exponents between morphometric measures (volume, area, shore length). These exponents are further compared to those expected from geometrical assumptions and constraints. Lakes cover a larger range of volumes for the same range of surface areas than reservoirs, and have a larger volume-area scaling exponent. The volume-area scaling exponent for reservoirs (but not natural lakes) and the area-shore length exponent for all water bodies follow the predictions for self-affine surfaces. Land cover and terrain influence the scaling relations more for lakes than for reservoirs. These morphometric differences may be used to model the impact of reservoirs and lakes on hydrological processes and associated ecosystem services at regional to global scales.

Assessment of the linkages between ecosystem service provision and land use/land cover change in Fincha watershed, North-Western Ethiopia

Fincha watershed is characterized by the presence of large scale government development projects, such as hydroelectric dam and sugarcane plantation. Within this watershed, land use/land cover (LULC) changes and its linkages with ecosystem services were analyzed for a period of more than three decades (1987-2019). The study first assessed LULC dynamics using ArcGIS software with a standard method. After data on LULC change was obtained, the study used a globally developed values coefficients to estimate the Ecosystem Service Values (ESVs) of the study watershed. The findings revealed that; cultivated land, water body, settlement and sugar cane plantation increased at a rate of 579.8 ha/yr, 199.7 ha/yr, 141.2 ha/yr and 137.1 ha/yr, respectively, whereas wetland, forest land and bare land reduced by 600 ha/y, 328.7 ha/yr and 60.3 ha/yr, respectively, for the study period (1987-2019) considered in the watershed. The increase in water body and sugar cane plantation is mainly attributed to large scale government development projects, while the increase in settlement and cultivated land is the result of small scale farming in the area. Both subsistence farming practices and large scale government projects compete on forest land and wetland. This has resulted in the decrease of the total NCV (Natural Capital Value) by 13.2%. The total ecosystem service values were dominated by cultivated land, which contributed 42.9% of the values in 2019. Elasticity of ESV change in relation to LULC showed the dominance of cultivated land in the overall values of the natural capital. To optimize the values of natural capital at the watershed, making synergies and tradeoffs between land uses is vital by all concerned stakeholders involved in modification of the land uses.

Hydro-climatic changes of wetlandscapes across the world

Assessments of ecosystem service and function losses of wetlandscapes (i.e., wetlands and their hydrological catchments) suffer from knowledge gaps regarding impacts of ongoing hydro-climatic change. This study investigates hydro-climatic changes during 1976-2015 in 25 wetlandscapes distributed across the world's tropical, arid, temperate and cold climate zones. Results show that the wetlandscapes were subject to precipitation (P) and temperature (T) changes consistent with mean changes over the world's land area. However, arid and cold wetlandscapes experienced higher T increases than their respective climate zone. Also, average P decreased in arid and cold wetlandscapes, contrarily to P of arid and cold climate zones, suggesting that these wetlandscapes are located in regions of elevated climate pressures. For most wetlandscapes with available runoff (R) data, the decreases were larger in R than in P, which was attributed to aggravation of climate change impacts by enhanced evapotranspiration losses, e.g. caused by land-use changes.