Inafirst, healthupdate onmangroves
200916 STUDY Report reveals failing health of Gorai, Sewri, Malad mangroves; state says lot changed in past two years MUMBAI:
The health of mangroves in various areas in Mumbai deteriorated between 2013 and 2016 owing to coastal pollution, a preliminary study of satellite maps released by the Indian Institute of Space Science and Technology (IIST), Thiruvananthapuram has revealed. These areas include Gorai, Thane creek, Sewri, and isolated patches of Malad, Versova and Vikhroli.
The first-of-its-kind report in India, developed over six months, was submitted to the state mangrove cell last week. The report, however, identified an overall increase in mangrove cover in Mumbai owing to siltation, which facilitates growth. HT had first reported in November 2017 that the proposal for the study was accepted by the state mangrove cell. The cell spent ₹51.09 lakh on the study which looked at calculating the health of mangroves by studying density, fragmentation, diversity, vegetation indices and other parameters. Satellite maps from 2009, 2013 and 2016 were compared using Normalised Difference Vegetation Index (NDVI) — an indicator of current health of mangroves. The findings need to be validated with on-ground surveys, the study added.
However, the state mangrove cell said the last satellite image was from 2016, and a lot had changed in two years. “There might have been some impact due to pollution. The report does not take into account the overall health from 2017 and 2018 when newly vegetated areas have come up,” said N Vasudevan, additional principal chief conservator of forest, state mangrove cell. Scientists however said the report was accurate. “NDVI values account for plant morphology, leaf shape, growth, the amount of moisture, etc. If there is more dryness, the leaves will not reflect any sunlight back to the satellite. The NDVI values will be low, indicating low health. The analysis depends on coastal pollution and tidal water inflow,” said G Kantharajan from Indian Council for Agricultural Research (ICAR), Central Institute of Fisheries Education (CIFE), Andheri.
The high resolution satellite images were developed with the help of ISRO, Hyderabad, said a senior IIST scientist. “A detailed analysis ofMumbai’smangroves health over 10 years and a realtime health report will be released in two years. We are developing an app that can track changes in real time.”
The civic body must carry out In 2009
The health of
Mumbai’s mangroves ranged between moderate and good across the city
PROBLEM AREAS: Isolated areas in Sewri, Thane creek and Vikhroli showed minimal deterioration Using high resolution satellite data (Landsat 8 and Sentinel 2) from open sources, Vegetation Health Index (VHI) was calculated. VHI is an indicator of current vegetation health of mangrove forests based on circumstantial conditions through satellite imagery, over three years. Higher values of Normalised Difference Vegetation Index (NDVI) show healthy mangroves
Category 0.6-1 0.3 – 0.6 0.1 – 0.3 Less than 0.1
Index Very good health Good health Moderate health Very poor health
(Source: Indian Institute of Space Science and Technology (IIST) in Thiruvananthapuram) city-wide drives focusing on mangrove restoration and garbage removal, said Arvind Untawale, executive secretary, Mangrove Society of India (MSI). “There has to be an analysis of the sites mentioned in the report to understand what has been happening,” said Stalin D, director, NGO Vanashakti. A high court order passed in September stressed on mangrove conservation. The petitioner, Debi Goenka, executivetrustee,ConservationAction Trust, said, “As pollution continues to rise and restoration measures are inadequate, the current health is likely to be worse.”
Colour Dark green Light green Orange Red In 2013
Mangrove forests showed significant health improvement.
Very good health reported from areas such as Versova, Malad creek, Gorai, Manori and isolated pockets of Thane creek
PROBLEM AREAS: Isolated patches in Sewri and Thane creek In 2016
While mangroves in Malad-Manori showed very good health, remaining parts of the city witnessed moderate to good health
PROBLEM AREAS: Areas such as Gorai, Thane creek, Sewri, and isolated patches of Malad, Versova and Vikhroli witnessed a decline in health with either very poor or moderate health The report also showed the health of mangroves in northernpartsofRaigad district was moderate to good in 2009, improved to good in 2013, but declined again in 2016 with small pockets recording very poor health
Overall, the report indicated a rise in mangrove cover across Mumbai irrespective of declining health over a span of eight years Coastal pollution
Blockages in intertidal regions stopping the flow of high tide water
Garbage accumulation Reclamation of mangroves and wetlands
Pest infestation
High salinity that all mangrove species cannot withstand
(Source: State mangrove cell, scientists and environmentalists)