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Bengal tigers could vanish from the Bangladesh Sundarbans in the next 50 years – by 2070 – as a combination of climate change and rising sea levels threatens their last remaining habitats, says a new study by a team of researchers from Bangladesh and Australia, published in the journal Science of the Total Environment.
Situated on the lower Ganges-Brahmaputra delta, up to 70% of the Sundarbans area is less than one metre above sea level, meaning rising water levels pose a significant threat to the low-lying tiger habitats.
Using computer simulation models based on two climatic scenarios developed by the Intergovernmental Panel on Climate Change (IPCC), coupled with projected sea level rise in the area, the researchers have assessed the future suitability of the Sundarbans region for tigers.
“While this is a preliminary analysis, we can conclude that the largest population of Bengal tigers is in an area where a combination of actors including climate change and human encroachment could both contribute to the decimation of habitats,” William Laurence, distinguished research professor at James Cook University and co-author of the study, told IndiaSpend.
Three of the eight sub-species of tiger have already become extinct, with the remaining five species currently either ‘endangered’ or ‘critically endangered’.
As global temperatures rise and melting polar ice raises sea levels, the influx of salinated sea water can make it harder for certain plants to grow, subsequently decreasing the availability of certain food types.
The Sundarbans’ spotted-deer population, a key food source for the Bengal tiger, is likely to be affected as the tree leaves on which it feeds begin to disappear.
The loss of the world’s largest mangrove ecosystem also raises concerns for human populations and other animal species.
Mangroves are an effective water regulation system, preventing shoreline erosion that also act as a shelter belt against cyclones and tsunamis. Villages surrounded by mangroves experienced less loss of life and capital during the 2004 tsunami, than those that were not, according to this 2005 Annamalai University study.
Each climate projection, based on two different levels of global greenhouse gas emissions used by the IPCC, estimates “a dramatic decline” in suitable habitats for the Bengal tiger.
Up to 49.7% of habitat loss is projected under the first scenario by 2050, and up to 96.2% under the second scenario.
Although sea-level rise will further threaten the Bengal tiger’s habitats, the effect will “not be as pronounced as climate change”, the study says.
Under both IPCC scenarios, sea level rise will contribute 5.42% and 11.3% habitat loss in the area, respectively.
The effects of rising sea levels and climate change in the Sundarbans delta area have been widely reported in recent years.
An increase in Bengali-speaking students in Kannada-medium schools in east Bengaluru, for example, may be the result of forced migration, IndiaSpend reported in December 2018.
Rising tides in low-lying areas of West Bengal are threatening traditional coastline communities, encroaching on buildings and negatively impacting agriculture.
The study calls on the Bangladesh government to designate more areas for tiger conservation, create corridors to help tigers move around the region more safely and continue monitoring illegal human activity in the area to avoid further losses.
However, while this study estimates total decimation of suitable tiger habitats in the next 50 years, not all experts believe the outlook is so bleak.
“I don’t subscribe to such a doomsday view,” said Sugata Hazra, professor of oceanography, school of oceanographic studies, Jadavpur University, Kolkata. “When we conducted our 2016 study, we accounted for a ‘sediment attrition rate’, since mangroves are also building land in the area as they attract sediment.”
“This has to be compensated for as well as sea level rise,” Hazra said, “Our study estimated maximum 17% area loss.”
Up to 40% of the Sundarbans region, a 4,000 sq km area slightly larger than Goa, is situated in West Bengal in eastern India. An estimated 103 tigers currently inhabit the area, which houses the Sundarbans Tiger Reserve.
However, some believe classifying part of the region and parts of the tiger population as Indian, and some as Bangladeshi, may be hindering conservation efforts.
A basin-level approach with closer cooperation on forest sharing, tiger habitat sharing and management of the freshwater supply is what is needed, Hazra said.
This article was first published on IndiaSpend and has been republished with permission.
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