Mumbai has 6,600 hectares (ha) of mangrove cover with 6,400 ha in the suburbs and 200 ha in south Mumbai.
Even as four species of mangroves have gone missing, Versova creek, with 10 species, tops the list of diversity in the city’s forests, followed by Gorai creek (8 species), according to a recent study. With only 2 species of mangroves, Bandra ranks the lowest.
Mumbai has 6,600 hectares (ha) of mangrove cover with 6,400 ha in the suburbs and 200 ha in south Mumbai. A study by scientists from the Indian Council for Agricultural Research (ICAR), Central Institute Of Fisheries Education (CIFE), Andheri, College of Fisheries, CAU (I), Lembucherra, Tripura, and National Centre for Sustainable Coastal Management in Chennai found four species – Lumnitzera racemosa, Kandelia candel, Sonneratia caseolaris and Avicennia alba – to be missing. The paper, Vegetative Structure and Species Composition of Mangroves Along the Mumbai Coast, was published last month in an international journal, Elsevie.
The team that studied 24 mangrove sites (each with a minimum area of 100sqkm) between August 2015 and May 2016 found a total of 10 true mangrove species belonging to five families and eight genera across the eight locations. “Apart from species composition, we studied the regeneration of mangroves and found that seedlings of rare species were present, but were not allowed to grow and become trees because salt tolerant species were more dominant,” said G Kantharajan from ICAR-CIFE, lead author of the study.
Around 75% of the city’s mangrove forests are dominated by one species, Avicennia Marina, a grey fruiting plant with dark green leaves. The rest of the area is occupied by Acanthus ilicifolius, Ceriops tagal, Bruguiera cylindrical, and Aegiceras corniculatum. “The prevalence of high saline conditions along the Mumbai creeks is why Avicennia Marina survives well,” said Kantharajan, adding the four missing species could not survive the environmental changes. “Earlier there were free flowing rivers that could provide freshwater for the survival of different mangrove species. However, with rising population there was a rise in domestic waste and sewage began entering these rivers turning them into nullahs. The water ingress from these areas became saline overtime. Thus, only hardy species could survive and withstand such conditions.”
HT had reported earlier this month that the number of mangrove destruction cases in Mumbai increased by 70% in the first nine months of 2018, compared to the past two years. The paper quoted two reports by Hindustan Times from 2015 and 2016 about mangrove destruction in Mumbai, and said the loss of mangrove species was directly a result of increased anthropogenic, or human, activities. Also, mangrove land is being illegally acquired for real estate development, said ecologists.
Composition of mangrove flora has adversely affected overtime that led to degradation of coastal creeks and mangroves. “Lack of understanding of spatial distribution and habitat requirements of mangrove species is the impediment in conservation efforts,” he said.