Application of pressure-state-response approach for developing criteria and indicators of ecological health assessment of wetlands:a multi-temporal study in Ichhamati floodplains,India

Background Tropical floodplain wetlands are among the most disturbed and intensively harvested ecosystems.Their sustainable management is often hindered due to the lack of comprehensive,coherent,and standardized assessment frameworks of wetland ecological health(WEH).In this study,a set of appropriate criteria and indicators(C&I)of WEH assessment was developed and tested on seven wetlands of River Ichhamati,eastern India.Methods Based on the pressure-state-response(PSR)approach,evaluation indicators representing ecological,socio-economic,and institutional sustainability issues of floodplain wetland systems were either selected or formulated through literature survey and stakeholder consensus.Weights of indicators were assigned by the entropy weighting method and then used in the Technique for Order of Preference by Similarity to Ideal Solution model to determine the Euclidean distances of each wetland from the positive ideal solution and negative ideal solution.Subsequently,a comprehensive wetland ecological health index(CWEHI)was constructed from these distances to portray the condition of any PSR system component in a wetland under a fivefold classification scheme,namely‘excellent health’(CWEHI≥0.81),‘good health’(0.61-0.80),‘moderate health’(0.41-0.60),‘weak health’(0.21-0.40),and‘morbid’(≤0.20).Results The developed C&I set contains 8 criteria and 38 indicators under pressure component,7 criteria and 49 indicators under state component,as well as 4 criteria and 18 indicators under response component.When applied in 2016 and 2022,it was found that the Panchita and Aromdanga wetlands were continuously in weak and morbid health status,while the Madhabpur wetland always showed an excellent or good status for all components.Health of other wetlands oscillated between moderate and morbid health across assessment years and system components.Conclusions The developed C&I set was found to be a flexible,holistic,and refined framework that could be applied elsewhere in similar assessments with minor indicator-level adjustments.The present assessment inferred that agriculture-dominated wetlands were more affected by amplified environmental pressure than fishing-dominated wetlands.Absence of persistent water flow from main river channel,wide-spread jute-retting,agriculture-induced eutrophication,proliferation of aquatic weeds were identified as the major causes of rapid ecological deterioration.

Spatially explicit estimation of soil organic carbon stock of an estuarine mangrove wetland of eastern India using elemental analysis and very-fine resolution satellite data

Background:This study estimated the total soil organic C(SOC)stock of the wetland influence zone of Bichitrapur mangroves in eastern India in a spatially explicit manner.Both spatial and vertical distribution of SOC densities with respect to land use/land cover(LULC)pattern were assessed.Subsequently,some site-specific management strate-gies were forwarded towards enhancement of C sequestration potential.Methods:The changing patterns of LULC within the wetland influence zone of the site were analyzed using Landsat TM(30 m)and Pleiades-1A(2 m)imageries from 1988 to 2018.Point-specific SOC measurement was done using samples taken from four core-depth intervals(viz.D1:0–20 cm,D2:20–40 cm,D3:40–70 cm,D4:70–100 cm)at 89 locations belonging to different LULC categories.Spatial interpolation was applied on this point-based data to produce SOC density and stock models as a whole and at all core-depths.Relationships between SOC density,core-depth and present LULC were evaluated through multivariate statistical analyses.Results:The LULC transformations during last three decades suggested the gradual growth of mangrove plantations as well as agricultural and aquacultural activities.Most amount of SOC was concentrated in D1(37.17%)followed by D3(26.51%),while D4 had the lowest(10.87%).The highest mean SOC density was observed in the dense mangrove patches(248.92 Mg ha^(−1))and the lowest mean was in the Casuarina plantations(2.78 Mg ha^(−1)).Here,Spline method emerged as the best-fit interpolation technique to model SOC data(R^(2)=0.74)and estimated total SOC stock of the entire wetland influence zone as 169,569.40 Mg and the grand mean as 125.56 Mg ha^(−1).Overall,LULC was inferred as a major determinant of SOC dynamics with a statistically significant effect(p<0.001),whereas no such inference could be drawn for soil core-depth.Conclusions:The C sequestration potential of sites such as the present one could be increased with appropriate zone-wise plantation strategies,restriction on the land conversion to aquaculture and promotion of ecotourism.Peri-odic monitoring through integration of geospatial techniques and elemental analyses would be immensely beneficial in this regard.