The death of a rodent doesn’t always spark concern. But when the Australian government declared the extinction of the Bramble Cay melomys last February, the news created ripples.
For the species, endemic to the Great Barrier Reef, was killed chiefly by sea level rise (SLR). It was the second such casualty; the first, four years ago, was when five small islands, a part of the Solomon Islands in the west Pacific Ocean, sank and vanished from the face of the map.
The phenomenon of rising seas has been observed all over the world, including India, and its impact explored in a special report published by the United Nations’ Intergovernmental Panel on Climate Change (IPCC) last September. The global mean sea level (GMSL) isn’t just rising but accelerating, says the chapter on ‘Sea level rise and implications for low-lying islands, coasts and communities’.
Is India equipped to handle the dangers posed by SLR? The country’s coastline stretches 7,500-odd km and runs past nine states, including state capitals. The east coast, hemmed by the Bay of Bengal, is often pelted by cyclones, and the hitherto placid Arabian Sea on the west warmed up to brew four cyclones last year — a first in over a century. A fifth of India’s population lives along the coast; Mumbai, one of its biggest cities, thrusts into the Arabian Sea rather gingerly.
The oceans have risen consistently and, worryingly, it has risen faster in recent decades. According to the IPCC report, if the GMSL rise was 1.4mm a year from 1901 to 1990, it rose to 2.1mm a year in 1970-2015. The rise accelerated to 3.2mm a year between 1993 and 2015, and 3.6mm a year between 2006 and 2015.
The projections are for a dire future; the mean sea levels are expected to rise steadily, hitting around half a metre by 2100. Tiny islands and low-lying cities might experience, what scientists call, extreme sea levels by 2050.
Where does that leave Mumbai, a city shaped from the sea?
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Water is the one element that defines — and wrecks — Mumbai. For a city that is home to an estimated 20 million people, Mumbai stands on shifty ground. Carved out of the Arabian Sea almost 200 years ago, the city was born when seven neighbouring islands were merged through engineering exercises into a single landmass. The prospect of the sea denting the land reclaimed from it is real for Mumbaikars.
Kapil Gupta, professor, department of civil engineering at the Indian Institute of Technology, Bombay, uses an analogy for the low-lying areas of the city — a bathtub. “We’ve filled up the low-lying areas with earth and later raised multistoreyed buildings on it, thereby reducing the holding capacity of those areas. When the water level rises, the bathtub will overflow,” says Gupta, one of the review editors of the chapter on ‘Sea level rise...’ in the IPCC report.
A large part of the city, Gupta notes, is just a notch above sea level. “In places such as Grant Road, even in summer during high tide, one can see water just a foot below the drains that empty into the sea.”
City residents can’t forget the floods of 2005, when Mumbai witnessed the worst deluge in its history. Relentless rain, coupled with storm surges and high tides, killed over 1,000 people. The city was flooded again in 2017. Recent studies have shown a three-fold increase in rainfall over the Western Ghats and central India.
Gupta introduces the prospect of SLR into this already volatile weather scene. When multiple factors — heavy rainfall, high tides and SLR — come in tandem, they spew disaster. “When it rains in coastal areas such as Mumbai or Kochi, and if tides are high during the time, water will not drain out immediately into the sea. In addition, if there is SLR, a few millimetres of water is enough to overflow and flood those living on the edge,” says Gupta.
SLR will impede the quick drainage of rainwater into the sea during times of high tide. “In the long term, it increases the chances of flooding for people living in low-lying areas, especially those living on the banks of rivers and drains emptying into the sea.”
While scientists agree that the sea levels are rising, the exact levels of that rise at different regions in the country need to be ascertained with greater accuracy. At the moment, Gupta says, we are dealing with global averages which definitely confirm SLR.
Tuhin Ghosh, one of the lead authors of the special report chapter, points out that data was the biggest hurdle when he tried to cull out numbers for SLR in India.
“There is a rise in sea levels in the Arabian Sea and Bay of Bengal coastlines. But to determine how badly it will impact us, we need estimates of the exact rate of rise. The range we have from India is too wide — anything between 3mm and 16mm,” adds Ghosh, an associate professor at the School of Oceanographic Studies, Jadavpur University, Kolkata. Scientists rely on exhaustive baseline data as well as advanced elevation data to arrive at projections, and India doesn’t have enough of either.
Ghosh emphasises the need for robust baseline data so that scientists and researchers in India will have something to bank on in the future. “Now we are trying to connect every kind of erosion with SLR. Erosion can be due to paucity of sediments or changes in hydrodynamic conditions. We have to consider all factors,” he adds.
To effectively measure SLR, scientists need both long- and short-term data, points out Roxy Mathew Koll, climate scientist at the Indian Institute of Tropical Meteorology, Pune. Scientists study long-term trends through tide gauges installed on the coast. “In some parts, for instance, at Colaba in Mumbai, we’ve had tide gauges for over 100 years. At the same time, at many other places, along the coast and open oceans, we do not have tide gauge networks. As a result, we don’t have enough data,” Koll explains.
However, things are slowly changing, and scientists are now banking on satellites to measure sea levels. But a new approach means the data collected is limited. To top it, the phenomenon of SLR also throws up inconsistencies, Koll adds.
“SLR changes have variability. Sometimes, they may not sync with a trend. At times, the levels may rise and even go down depending on global ocean changes or alterations in heat and circulation. But in order to have a better understanding, we need to have a much more dense network of gauges,” he adds.
For scientists studying the phenomenon, the absence of solid elevation data — which map the elevation of land from the sea — is another problem. Even cities such as Mumbai, prone to SLR and storm surges, lack such data. “It is the reason why we have uncertainties in the projections of SLR along Mumbai and the rest of the Indian coast,” Koll says.
Even though scientists are saddled with sparse data, emerging research continues to sound the alarm. Koll, who is leading studies in the Indian Ocean, highlights its rapid and consistent warming. Melting glaciers are known to raise sea levels, as are warming oceans. “In the tropics, SLR is largely due to ocean warming. As the temperature rises, the volume of water expands,” Koll says.
The Indian coastline is up for rough weather on that count. Compared to other seas, the Indian Ocean has been warming consistently every year for over 50 years; the average temperature rose by a degree Celsius in 1951-2015.
“The global average surface temperature change is 0.7 degree Celsius for the same period,” Koll points out. Recent satellite estimates, he says, put SLR at 3-5mm a year. “We have to be aware of recent changes because the ocean is warming rapidly,” he warns.
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While scientists wrestle with numbers, Ulka Kelkar, climate director at World Resources Institute (WRI) in Bengaluru, puts the issue in perspective. “Data will never be perfect. But the question is, should it stop us from making sensible decisions?”
On one hand is the science of SLR, and on the other, she says, ways to combat it. Limited data, Kelkar insists, should never come in the way of thinking up solutions.
Practical evidence of warming oceans and SLR rests in the anecdotes scientists share. E Vivekanandan, a scientist who retired from the Central Marine Fisheries Institute, recalls the time when sardines, a fish typically found in abundance along the Kerala and Karnataka coast, began to be seen in the east coast as well as further up the western coast. All of a sudden, large schools of sardines landed up along the Gujarat and Maharashtra coast, throwing fishermen off guard. There was little demand for the fish in these states.
“Oil sardines prefer higher temperature — above 28 degrees Celsius. When the seas began to warm, the fish could expand their territory and travel,” Vivekanandan says. The phenomenon was noticed in the late 1980s and in terms of numbers, sardines are now the top fish landing in some areas on the east coast.
Warming oceans may have introduced sardines to new aficionados. But rising ocean temperatures are worryingly altering the lives of fishes. The reproductive cycles of certain fish have changed with the oceans heating up, Vivekanandan says. Fish such as the Indian mackerel usually spawned in peak summer. With summer temperatures shooting up, the fish is now spawning a month or two earlier than they did a few years ago.
“The normal spawning season is adjusted to the time when there is enough food in the sea. When that changes, it is likely the larvae may struggle to find food,” Vivekanandan says.
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Rise in sea levels and their effect on fish cycles extract a human cost, too. Rising temperatures have led to the advent of new species of fish on different coasts, leaving fishermen confused about how to market them. Any change in the sea, be it a rise in the waters or a change in temperature, disrupts the livelihood of the coastal community, an important stakeholder on the coast and the seas.
“The people share an intense socio-cultural connect with the sea,” says senior WRI manager Lubaina Rangwala, who studied the impact of climate change on the coastal community in Arnala, a fishing village in Mumbai region. “Their festivals are centred around it, their friendships and social associations are woven around the sea. When fishing gets difficult, families struggle to transition away from it,” Rangwala says. And that is why, she says, those communities need rehabilitation when SLR disrupts their livelihood.
SLR, however, is not yet a part of the national climate conversation, not in the way, say, melting glaciers are. There is very little discussion on SLR in the national action plan on climate change (2008).
The affected states, though, have been evolving ways to combat, mitigate and address the problem. SLR is priority in the climate action plans of Maharashtra and West Bengal. Rangwala draws attention to the Water Policy of the Kochi Corporation that addresses SLR and even the rehabilitation of the population along the coast.
“Focus shall be on preventive planning, adaptive management techniques and allocation of future land use, keeping in mind the probable inundation zones,” the policy says.
Goa is another state deeply affected by changes in the sea. Ashwini Pai Panandiker, a fellow at The Energy and Resources Institute (TERI), who studied the climate resilience of infrastructure in Panaji in the event of SLR, has identified danger areas.
“We studied the climate resilience of man-made and natural structures to come out with a vulnerability map, identify areas that might get inundated and those that need intervention,” says Panandiker. The 2015 study also looked into climate efficiency of structures designed for future.
Significantly, she says, they came up with a database management system making climate data accessible to different departments. “The data was collected during the two-year period of the project and handed over to the corporation of Panaji,” she adds.
Kelkar of WRI points out that in the wake of events such as SLR, mitigation measures are often chalked out, but are slow to be implemented. After the 2005 Mumbai floods, a massive programme was launched to widen its stormwater drains and allow better drainage of rainwater. According to news reports, 14 years later, only 27 of the 58 drains earmarked have been upgraded.
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SLR poses two kinds of challenges, says Kelkar. One is the physical task of protecting a vast and vulnerable coast. The other is addressing the social repercussions of the event.
“Historically, we have had a fertile coastline and also a huge concentration of population along the coast.” SLR doesn’t merely raise the prospect of inundation of land, but also saltwater intrusion into crops. “We will suddenly find that salinity levels are not what the crop varieties are designed to tolerate,” she says.
Kelkar recommends a combination of community-level action as well as planned responses from the states to effectively combat SLR. The problem often tends to be region-specific and may need curated local responses.
“However, the problem with leaving everything to local communities is that the responses tend to be reactive rather than proactive. For instance, preventive measures will be thought of only when the rice fields are filled with salt water or the sea is creeping up to where the houses are,” she points out.
It is at this point, Kelkar says, planned response from the state or local administration will make perceptible changes. These “proactive” responses can range from agriculture universities researching on crop varieties that can withstand salinity to equipping the fishing community with effective warning systems for cyclones and other disturbances.
Among planned response is a stricter enforcement of coastal zone regulations (CZR). “When we have CZR we should not dilute or violate them,” she says, drawing attention to the widely circulated videos on WhatsApp that showed the implosion of high-rises in Kerala built in violation of regulations.
Gupta, too, agrees that massive infrastructure projects along vulnerable zones must stop. Combating SLR involves expensive options such as building seawalls and natural alternatives such as mangroves.
A small and wealthy country such as the Netherlands — a third of which lies below sea level — has responded with high-tech seawalls. “After the Mumbai floods, a six-metre-high flood wall was built along the Mithi river. But structural interventions are expensive,” adds Gupta. Non-structural measures include tidal gauges at outlets to rivers and estuaries.
Koll refers to the local people of the Gulf of Mannar who are diligently restoring acres of sea grass to protect the gulf from high waves.
Clearly, there are many solutions. But prudence and careful living have few replacements, the experts stress. Kelkar draws from the Chernobyl disaster — now an HBO film — to make a point. “It’s never one thing that causes a disaster, but a chain of bad decisions. If you are disturbing everything, eroding away natural buffers, you are putting yourself at risk.”
And, sometimes, just a few extra millimetres of water can cause havoc.