Raise the ground, regrow the reef

On an afternoon in the rainy season the storm clouds stand like a high wall behind the island, yet the sun is still on the reef flat. A short jetty and one small boat are all the harbour there is: this is the only landing for the few dozen households who live here. In this low archipelago in the tropics most islands rise less than three metres above the sea. Last week the island nation's ocean department published a thirty-year adaptation plan with a single question to answer: as the tide creeps higher year by year, how is home to be kept?

The plan took two years to draw up, with more than forty village meetings on the seventeen inhabited islands. It does not take up the option of moving everyone away: most residents will not leave the fishing grounds their forebears left them.

What the measurements say

The plan's monitoring report shows the sea around the islands rising by about four millimetres a year over the past twenty years. On the reef flats that take the force out of the swell, live coral cover has fallen from a half to roughly three-tenths. With the reef weakened, a storm surge of the same strength reaches tens of metres further inland, and on the lowest islands the well water has begun to taste of salt.

Three stages

• The first five years: strengthen the jetties and cisterns of all seventeen islands, and lay the ground of every new house and road one metre above the highest tide on record.
• Years six to fifteen: gather schools, clinics and power plant on three larger islands whose reefs are intact, and bring rainwater tanks and small desalination units to every settlement.
• By year thirty: transplant 600,000 heat-tolerant corals, restore ten kilometres of natural barrier and halve the fresh water drawn from underground.

"We are not trying to stand taller than the sea. We are buying the reef time to grow back by itself," says a coastal engineer who helped to draw up the plan. His team has been planting heat-tolerant coral on two islands, and after three years nearly seven in ten have survived.

The change has reached the classroom too. The island primary school has put the tide into its maths lessons: pupils read the gauge at the jetty every morning and evening, more than 700 readings a year, all fed into the department's monitoring system. "When the children talk about a rising tide now, they use centimetres," says one of the teachers, "not big and small."

The first works begin next dry season with the jetties and cisterns. The department will publish its measurements to residents every five years and revise the arrangements to match.