Spatio-temporal modelling for the evaluation of an altered Indian saline Ramsar site and its drivers for ecosystem management and restoration

Abstract

Saline lakes occupy 44% and 23% of volume and area of all lakes. These lakes might suffer from extended dryness, reduced hydroperiod, or complete desiccation by 2025 influencing billion-dollar global markets of salt, shrimp, and minerals besides environmental disruption. India ranks third in global salt market exporting approximately 230 million tons to 198 countries. Current study is conducted in Sambhar Lake, largest inland saline Ramsar site contributing 9.86% of total salt production. The lake is undergoing partial desiccation due to illegal saltpan encroachment stealing brine worth 300 million USD. The current study aimed to assess its trend of degradation, identify ecological indicators, and predict future status. So, geospatial modelling was conducted for 96 years (1963-2059) using supervised classification, Cellular Automata-Markov model, birds-soil-water data. Land Use Land Cover classification was conducted using CORONA aerial imagery of 1963 (before start of any satellite mission) and Landsat satellite imageries for 1972, 1981, 1992, 2009, 2019 and future prediction for 2029, 2039, 2049 and 2059. Images were classified into 8 classes as Aravalli hills, barren land, saline soil, salt crust, saltpans, waterbody, settlement, and vegetation. Past trend shows reduction of waterbody from 30.7 to 3.4% at constant rate (4.23%) to saline soil. Saline soil increased by 9.3% subsequently increasing barren land by 4.2%; saltpans by 6.6% and settlement by 1.2% till 2019. Future predictions show loss of 40% wetland and net increase in 30% vegetation, 40% settlement, 10% saltpan, 5% barren land, and net loss of 20%, each by Aravalli and salt crust by 2059. Additionally, soil-water-birds census result state a loss of its saline character; subsequently reduction of migratory bird. Saltpan-encroachment, groundwater extraction, hydrological structure construction, and water diversion, have altered its water budget, hydrological communications, habitat, and productivity. In the light of UN Decade on Ecosystem Restoration (2021-2030), restoration strategies are suggested, if delayed, more restoration capital may be required than its revenue generation as happened in the case of Owen’s lake in California when US$ 3.6 billion was spent for its dust mitigation for 25 years.

Migratory Birds Monitoring of India’s Largest Shallow Saline Ramsar Site with Big Geospatial Data Using Google Earth Engine for Restoration

“…Their decreasing trend in this lake indicates the disturbance in the respective organisms of lower trophic levels. Disturbance in the organism configuration is the visible result of changing abiotic factors like pH, salinity, alkalinity, oxygen and carbon dioxide and disturbed landscape variables wetland shape, size, patch, corridors and hydrological connectivity between shoreline and core part of the lake [10]. All these factors primarily indicate the highly fluctuating water level as shown in the monthly water index maps of 2019, 2020 and 2021 coinciding with our bird survey time frame.…”

“…As there used to be no water, it has often been used as vehicular testing sites which cause noise pollution in the peripheral area (Kumar, 2005). Based on the wetland status till January 2019, it has been predicted that the lake might be completely desiccated by 2059 even losing its saline character [10]. This will ultimately reflect on the global level ecological disconnectivity led by the migratory birds.…”

“…It is located 80.7 km away from Jaipur, the state capital of Rajasthan via National Highway 48 and Rajasthan State Highway 57 [36]. In 1961, the Government of India (GoI) took over this region on a 99-year lease under the Ministry of Commerce and Industry Salt production, as India exports approximately 230 million tons of salt to global market after China and USA, to 198 countries like Japan, Bangladesh, Qatar, Indonesia, South and North Korea, Malaysia, U.A.E, and Vietnam [10]. Being an inland wetland, it is 230 km 2 (22.5 km in length and 3-1 km in width) [37].…”

“…There are about 1 lakhs waterbird primarily flamingo overwintering in this lake and most of them are distributed in the saltpan areas as there is a little water left in the natural wetland area [44]. The water level of this lake is decreasing due to illegal saltpan encroachment [10]. Moreover, it also provides shelter to rich floral diversity such as species of 37 herbs, 14 shrubs, 14 trees, 15 grass, 6 chlorophyceae, 25 Cyanophyceae and 7 Bacilariophyceae [45].…”

“…Consequently, there more budget will be required for their restoration compared to the revenue generation as in case of Lake Owen's for Los Angeles city [9]. Even if these are vital aquatic ecosystems providing wide range of ecosystem services, habitat for lakhs of migratory birds and haloalkaliphiles, they are ignored compared to their freshwater counterparts [10], primarily due to their geographic locations in inaccessible areas [11]. However, since the launch of firstever satellite in 1972, application of Remote Sensing and Geographic Information System has enabled to conduct landscape-level studies due to availability of real-time, cost-effective, and dynamic satellite images significantly different from traditional in situ measurements [10].…”