Hotter, wetter and extreme story of Odisha's Bhitarkanika in 2050s
Year: 2050.
Place: Bhitarkanika Mangroves.
The seasons have grown hotter. The wet days are rainier than ever, and dotted with storms and tidal surges. The winter does not have the bite of the chill anymore. The mangrove vegetation is stressed with a rise in pollutants and decreased flow of freshwater from the catchments. The ‘salties’ are crammed with reduced space in their creeks. Rookeries for the Olive Ridley sea turtles have reduced due to erosion. The sea level has risen by about 50 cm.
Much as it seems like doomsday prediction, climate change can impact biodiversity hotspots in ways we cannot even imagine. The latest climate vulnerability assessment portrays a grim future for Bhitarkanika, one of India’s most unique and finest mangrove ecosystems, which is hard to ignore.
Bhitarkanika is among the last few remaining mangrove ecosystems in India with over 70 species. In fact, 55 of the 58 Indian mangroves species are endemic to this ecosystem. The study “Climate Risk Assessment of Bhitarkanika Mangroves, Odisha” devises climate change projections such as temperature rise, precipitation, extreme events and sea-level rise before assessing their impact and as well as vulnerability of the critical wetland system and its various actors.
Temperature Rise
As per the projections, average temperature in Bhitarkanika, a designated Ramsar site, may see a rise between 1.9 degree Celsius and 2.1 degree Celsius. Taking the 1960-1990 as the baseline period, the report says that summer in 2050 will have become hotter – the temperature rising from 33.5 degree C to 35.6 degree C.
The monsoon season too would report a rise in mercury from about 31.6 degree C to 33.5 degree C. Winters, naturally, will follow suit and be warmer with the temperature marking a 2 degree C jump on an average – from 27.6 degree C to 29.6 degree C.“Summer will be an extreme season with limited rainfall and high temperature, which will place stress on the forests and associated species,” says the report.
The projections look at the change in maximum day temperature in the three seasons February-May, June-October and November-January in Baitarani and Brahmani river basins. It’s these two rivers which continuously feed fresh water to Bhitarkanika during the south-west monsoon season. Their catchment being vast, the flow of freshwater and its characteristics have a huge bearing on the hydrological regime of the wetland which provides key ecological services, is home to diverse families of flora and fauna and sustains a 2.5 lakh large community dependent on fisheries as well as tourism sectors.
Changing Rainfall Trend
In the next 25 years, the report points at changes in the rainfall pattern, thanks to climate change impact. During the monsoon season, the total precipitation is likely to increase by close to 3.9 per cent. During the June-October period, the rainfall will rise by 48.3 mm, from 1,262.2 mm to 1,301 mm in 2050. This increase will be more pronounced in the upstream areas, almost by 11 per cent.
However, during the summer season between February and May, the rainfall is projected to drop by 8.2 pc or 13.7 mm – from 167 mm to 153 mm. A marginal decline of 5.5 pc is also calculated during the November-January phase. This decrease will be more significant in mangrove forested areas compared with upstream catchments, says the report which is prepared by International Climate Initiative, GIZ with support from the Odisha government.
While decline in rainfall during summer and winter seasons will have its outcomes, the rising temperature can hinder the physiological processes, including reduced leaf formation caused by a decline in photosynthesis which can also impact mangrove productivity.
The combined impact of rising temperature and drop in precipitation during two seasons can pose drought hazards. “The drought conditions in 2050s will be more severe compared to the baseline period. Poor rainfall can directly affect mangrove productivity, growth and survival by increasing salinity levels in the mangrove forested areas,” it says.
Climate change will induce frequent cyclones and storm surges and their intensities too, though mangroves have been an unwavering wall against natural calamities. Bhitarkanika stares at high risk of cyclone frequencies and a ‘moderate high’ risk of storm surges up to 5 metre. By 2040, sea level is expected to rise by 0.5 metre along the mangrove system’s coastline.
Impact on Mangroves
What do these changing parameters mean for the mangroves? The state government has done an admirable job in improving mangrove coverage area by encouraging plantation, diversity and protection but growing population pressure, changes in freshwater flow, encroachment, pollution and hydrological regime continue to be points of stress.
By 2050, the study of extent and health of the mangroves reveals that gross primary production (GPP) will have fallen by 7.7 pc while leaf area index will drop by 20.83 pc. Similarly, leaf chlorophyll will witness a 20.96 pc decline as compared to baseline values.
“Despite the conservation efforts, the current extent of dense mangroves will decrease by 10 pc. By 2050, patches of mangrove along south-west and northern coasts of Bhitarkanika Sanctuary are projected to decrease in gross primary production and are at a higher risk of disturbance,” the report says.
Already, denudation and saline blank formations are increasing in the forest blocks of Bhitarkanika. Higher rainfall in the upstream during monsoon may lead to erosion, waterlogging which would end up leaving little space for highland wildlife species such as deer, wild boars and reptiles. Similarly, sensitive species such as shrimps, crabs, frogs and fishes may face decline due to pollutants and sedimentation. On the other hand, drop in precipitation during summer and winters would lead to loss of productivity of mangroves which can directly impact food availability for fish and saltwater crocodiles. The crocodiles are at the top of the food chain.
Crocodiles and Olive Ridleys
The report says increased rainfall and flooding caused by climate change will lead to reduced mud banks, the basking beds for the saltwater crocodiles. With sea-level rise, these spaces may further decline sending the reptiles to outside of the protected area, thereby exacerbating man-animal conflict.
Habitat and food availability apart, impact of climate change on crocodiles could be more complex as it would leave lasting effect on nesting, hatching and survival of the juveniles. With rising temperature, the young crocodiles would spend less time diving into water and more outside to bask which would expose them to predators. As it is their survival rate in nature is very low.
The increasing temperature during incubation which spans from March to July may also change gender balance of hatchlings, leading to more males being produced. This could have long-term impact on populations of the ‘salties.’ Currently, their population at over 1,700 has been a stable one.
The vulnerability assessment also looks at the rookeries for Olive Ridley sea turtles. Sea-level rise, increased storm surge and cyclone frequency would lead to erosion of the nesting grounds which already stand reduced. This may force the marine species to seek safer places in other parts. Like the crocodiles, the turtles may go through a change in gender balance which could have implications on their global population, says the report.
Local Community
It’s the mangroves which make Bhitarkanika such a great nursing ground of fishery resources which sustains a local community of 2.5 lakh population. With the cascading impact of climate change, fish production and diversity can witness changes. This, in turn, would impact a large population of migratory birds as well as the fisher communities. Lower productivity and catch can lead to loss of livelihood.
Extreme events will impact tourism which is booming in the Ramsar site. Tourism which is a secondary livelihood source for the villages could come under shadow due to rising temperature, increased flooding and cyclones which would impact the tourism infrastructure.
The current threats of salinity increase due to sedimentation at river mouths and reduced water flow from the catchment must be addressed. Illegal inland aquaculture which has witnessed more farm fields being converted into prawn farms must be checked.
A study by Centre for Land Resources Management, School of Natural Resources Management at Central University of Jharkhand had reported that aquaculture has increased from 20.76 sq km in 2002 to 44.86 sq km in 2018. Pollution load from industries in the upstream is another issue that also needs attention to protect the wetland as well as agriculture in the villages surrounding the eco-system.
The report says the vulnerability assessment provides a way forward for greater stakeholder engagement, planning and research to generate climate adaptation measures to protect mangroves, flagship species as well as critical sectors such as fisheries and tourism.
A slew of adaptation and mitigation measures are already under implementation by the government but continued monitoring, survey and research will be required to keep this jewel of the state immune from vagaries of climate change.