Keeping the sea at bay

As sea levels rise due to climate change, planners in nations around the globe are trying to safeguard their coasts, but there is no consensus on the best way to do so

Retired headmaster Badruddin Sarkar is busy planting mangroves on the edge of the Sundarbans in West Bengal in eastern India. “Tides are getting higher. This is the only way to save my farm, my home, my island,” he says.

The first recorded climate refugees in the US have been shifted in Louisiana. Their old homes are now outside the wall built to protect New Orleans from the rising sea.

The city fathers in Dordrecht in the Netherlands are wondering if they should tell residents the bad news. “Our studies forecast that our embankments may not be able to keep water out of many houses after 2050,” says a municipal official. “We have given some information to residents, but we don’t know how they will react if we emphasise this.”

“We’re not depending only on our barrier to keep out the sea,” says an official at Europe’s busiest port Rotterdam, as he points to the showpiece barrier that can be raised to let ships in. “We’re always studying the tides and currents, and pouring sand along the coast in a calculated way, so that the water is diverted away from Rotterdam.” The trouble is, the diverted water may then cause more havoc in cities like Dordrecht, which are economically less significant.

The rising sea affects people in two ways. One, it erodes the coast. Two, it leads to more frequent and intense high tides and storm surges.

Sea walls and embankments, or mangroves and sand and coral reefs – planners around the globe are debating the best way to protect their coasts as sea levels rise due to climate change. With over 40% of humanity crowded along coastlines – especially in coastal cities – and with sea levels already having risen between 2.6 and 2.9 millimetres a year since 1993 as the earth warms up, protecting the coasts has become urgent.

It was a matter of much debate at the May 10-13 Adaptation Futures conference in Rotterdam. By and large, planners from the rich nations of the temperate region have opted for sea walls and concrete embankments. New York is strengthening its walls after Superstorm Sandy, Louisiana has built the wall that became a major demand after the 2005 flooding, London has a floating wall that is the pride of the city, Rotterdam has the boom. Now planners from the developing world are wondering if they should do the same. Should Mumbai, Karachi, Shanghai or Rio de Janeiro have similar high walls? How high would the wall have to be? Can they afford it?

As some experts pointed out at the conference, there is another way; control the erosion and temper the fury of the waves by planting mangroves or sea grass along the coast, protecting coral reefs or dumping sand to direct the currents away as the Dutch have been doing for hundreds of years.

Doing nothing is not an option

The debate was not resolved, as it became clear there is no single solution for all coasts. For one, neither mangroves nor corals grow outside tropical waters. If you build a high sea wall, beach tourism suffers and so does the value of real estate. And anyway, how high would such a walls have to be? There is a wide range of forecasts on how the seas will rise due to climate change and by when. It is difficult to make decisions amid such uncertainty, though most planners agree that doing nothing is no longer an option.

The consensus that seemed to emerge at the conference was that a combination was best. First use the softer options like planting mangroves and protecting coral reefs. If that does not seem to be working, build walls and embankments, especially for cities and other valuable property.

Far away from Rotterdam, Badruddin Sarkar stands atop the 5m high brick embankment that protects his home and farm from the rising sea in Bali Island, which faces the Bay of Bengal on the edge of the Sundarbans.

“I used to teach geography,” reminisces the former headmaster of the village school. “We were never taught that the sea could rise like this. Nor did we teach this to our students. This is a new world, where we cannot live. Do you see that tree stump? That’s where my house used to be, before the sea engulfed it and we were forced to move back.” Sarkar points at a stump that is barely visible among the breakers.

A series of waves crashed over the embankment during the next cyclone. Saline water ruined Sarkar’s rice fields and freshwater pond. The family has moved to Kolkata. They are climate refugees too, unrecorded.