BHUBANESWAR: Bhitarkanika Wildlife Sanctuary, a major coastal eco-system and home to one of India's biggest estuarine crocodile habitats, is witnessing an alarming denudation in large tracts of mangrove vegetation.
Such is the pattern that these saline blank formations in several forest blocks of Bhitarkanika have turned into a management challenge for forest officials and ecologists alike.
Physical evidence gathered from the mangrove forest division has revealed that such denudation (or saline blank formations) have been noticed in Bhitarkanika forest block which is measured at 1700 acre. The denuded patches, spotted in Mathadia, could be over 30 acres in this block alone.
Across many of the 15 forest blocks, such blank formations are being reported lately, causing an alarm among the ecologists. Mangroves are not just the lifeline for the unique eco-system which is home to a rich flora and fauna, but also act as an environment cushion for the coastlines.
The denudation has been noted among the Avicennia and Excoecaria species, popularly known as Bani and Guan.
Sources said, the saline denuded patches could be caused in the upper elevated zones due to inadequate inundation which leads to hyper salinity. The excessive salinity creates a blank formation over a period of time as the existing vegetation dies.
"Though mangrove species are saline-tolerant, inadequate inundation leaves a salt crust on the embankments which leads to gradual withering away of the mangrove vegetation," experts pointed out.
Most mangrove species have a salinity resistance that ranges from five ppt to 35 ppt. Only Avicennia marina species can tolerate up to 70 ppt salinity. In Bhitarkanika's forest blocks, the Avicennia marina species are found surviving amidst the infestation of weed species.
A major threat for the mangrove species is apparently the saline embankments created by government departments which hinder the inundation process. To protect the human habitations against tidal ingression, these embankments are slowly proving a disaster for the mangrove ecosystem.
Such saline blank formations were reported in past too and creation of fish bone channels helped in several blocks. In Kantiakhai, near Wheeler Islands, fishbone channels were created to allow the tidal inundation. Similarly, in Ranahansua near Habilikhati, restoration measures were also taken.
Sources say, alternatively these blanks can be managed to be converted into meadows to augment forage for herbivores which will minimise crop raiding which is now a menace.
The Forest Survey of India-2013 report had pointed out a drop in mangrove cover in the State by nine square km over 2011 - from 222 sq km to 213 sq km. In Kendrapara district alone, where most of Bhitarkanika is located, the drop was by four sq km while in Bhadrak, it was two sq km.