A week after the International Day for the Conservation of the Mangrove Ecosystem, celebrated every year on July 26, a delightful development occurred at Kattur village in Tiruvallur. Camera traps set up in a mangrove restoration site on the banks of the Kosasthalaiyar captured the images of a spotted deer and a wild boar, indicating a resurgence of biodiversity. This followed two years of restoration work by the Mangrove Foundation of India, a non-governmental organisation, which is restoring over 30 acres of land at Kattur.
Mangroves are unique shrubs or trees that thrive in brackish water, where salty seawater mixes with freshwater. These plants are typically found in the intertidal zone, an area between high and low tides. Their intricate root systems allow them to breathe in waterlogged conditions and stabilise shifting soils. Unlike most other trees, mangroves can adapt themselves to varying levels of salinity, making them well-suited to tropical and subtropical coastal regions.
A bio shield
Mangroves act as a natural buffer, protecting coastlines from cyclones and tsunamis by stabilising the shoreline and reducing erosion caused by storm surges, currents, waves, and tides. Their intricate root systems offer food and shelter to numerous marine species, including fish, amphibians, reptiles, birds, and even mammals like tigers and boars.
The economic potential of mangroves is significant, contributing to recreation, tourism, and national revenue. Known as the “dancing trees of the sea”, mangroves significantly reduce wave height, thus protecting homes and infrastructure from floods. During the 2004 tsunami, the Pichavaram mangroves in Tamil Nadu are said to have protected nearly 1,700 people from a severe impact. Similarly, according to a report published in The Hindu, mangroves demonstrated their protective role during Cyclone Gaja in 2018.
According to the Indian State of Forest Report, the extent of mangroves has doubled from 23 sq. km. from 2001 to 45 sq. km. in 2021. The mangrove ecosystems in the State extend across 11 coastal districts, with significant concentrations in Thanjavur, Nagapattinam, Tiruvarur, and Cuddalore. Together, these districts account for 84% of the State’s mangrove area. However, the total mangrove cover in the State is just 44.94 sq. km., which is less than that of the other eastern coastal States such as Andhra Pradesh (405 sq. km.), Odisha (259 sq. km.), and West Bengal (2,114 sq. km.).
Reduced tidal flushing and siltation
Pichavaram, in Cuddalore district has experienced significant changes in its mangrove ecosystems over the decades, largely influenced by human intervention and natural processes such as reduced tidal flushing and siltation. The period between 1987 and 1998 saw notable shifts in the mangrove cover, thanks to the proactive measures initiated by the Tamil Nadu Forest Department, along with institutions like the M.S. Swaminathan Research Foundation. These measures included detailed hydrodynamic studies to identify areas that needed dredging and trenching to improve water flow. By 1998, the mangrove area increased, reflecting successful restoration efforts.
The Pulicat Lake, once known for its dense mangrove forests, has also faced significant degradation. Historically called Pazhaverkadu, meaning “forest of the rooted fruit”, the mangroves were severely reduced, owing to activities such as the construction of the Dutch Fort in the 1600s and later urbanisation and industrial expansion.
In 2012, a community-driven reforestation effort, supported by the Global Nature Fund and CReNIEO (Centre for Research on New International Economic Order), began restoring Pulicat’s mangroves. This initiative initially resulted in a substantial growth, with more than 5,000 plants replacing the original 100. However, the 2015 monsoon caused a historic flood, which submerged the mangroves for 10 days and wiped out 90% of the restored plants. Despite this setback, efforts are being made to restore the mangroves on the Ennore-Pulicat wetlands, which were impacted by an oil spill in December 2023.
Mangroves, which can tolerate high salt levels, still require fresh water to survive, and prolonged submersion in saltwater led to their deterioration. Now, the Forest Department and non-governmental organisations are working to restore mangroves at various sites of the Ennore-Pulicat wetlands.
Areas identified for restoration
Tamil Nadu has open mangroves covering 16.88 sq. km, moderately dense mangroves spanning 26.95 sq. km, very dense mangroves on 1.11 sq. km. According to Ecological Sensitive Area mapping, conducted by the National Centre for Sustainable Coastal Management, based on the Coastal Zone Management Plan, 2011, and the satellite images prepared under the Tamil Nadu Wetlands Mission, there exists a potential for restoring 100 sq. km. of the mangrove ecosystems across 14 coastal districts.
Over the past decade, a decline of 34.92% and 11.83% has been noted in Thanjavur and Tiruvarur districts respectively, according to the National Centre for Coastal Research (NCCR).
Meanwhile, the NCCR has identified potential areas for restoration and rehabilitation using remote sensing data, followed by ground truth verification. According to its report, prepared for the Department of Environment and Climate Change, more land is available in Cuddalore (43 hectares), Tiruvarur (37 hectares), Thanjavur (811 hectares), Pudukkottai (62 hectares), Ramanathapuram (141 hectares), and Thoothukudi (215 hectares). “Protected areas like the Palk Bay Dugong Conservation Reserve in Thanjavur and Pudukkottai districts, and the Gulf of Mannar Marine National Park and Biosphere Reserve can be chosen for mangrove restoration, as monitoring is easy,” the report says.
Published - August 06, 2024 10:24 pm IST
