Frederica Boswell, BBC News 13 Dec 07;
People living close to beaches on the Tanzanian archipelago of Zanzibar fear they will lose their homes to the encroaching waves.
"The tides in October were the worst. All the tables and umbrellas were washed away," says Abdullah, a regular at the Mnazini guest house on Matemwe beach.
With each spring and autumn equinox, the new and full moon tides have been getting higher and more damaging to Zanzibar's north-east coast.
"Last month, the waves were almost four metres high as they hit the shore," said Kahindi Kadogoh, a local building contractor who has been based on Matemwe beach for over 15 years.
Using three large steps, he marks out how much the shoreline has receded in this time.
"When I came, the shoreline was here, and now it has gone back nearly three metres."
Building defences
Recently, the head of the United Nations Environment Programme warned that Africa's coastline faces increasing danger of erosion from rising sea levels caused by climate change.
"By some projections of the IPCC [Intergovernmental Panel on Climate Change], global warming could affect one-third of Africa's coastal infrastructure by the end of this century," said Achim Steiner.
"We know that we are on a course of having sea levels rising between 20 and 60cm this century."
Zanzibar's Chief Environmental Officer Asha Khatib is very aware that sea erosion is a cause for concern on the island.
"People come to the department with their government representative and say that they are worried. We need money but we must find ways to protect the shoreline as best as we can."
For the moment, all they can do is warn people not to cut down trees, build too close to the beach, or remove sand.
Officials say they are studying the problem and promise that a plan will be put in place when the study is completed in 2009.
In the meantime, those who can afford it have started building up defences, using concrete, coral or coconut poles.
Mr Kadogoh points these out as he walks down the beach, past hotels and private houses.
Stopping at a concrete slope, he explains that the idea is for the waves to break against it, and then roll over, as it provides a barrier for any sand being washed away.
Evident cracks
In theory, it should work, but as the tides get higher, the waves roll over it completely.
A high concrete wall looming over six-foot tall seems a solid defence against the power of the sea, however its cracks are evident.
"Zanzibar's biggest wave in over 55 years hit this wall in October and caused big damage," he says.
"It cannot resist the big waves because the cracks make it weak."
Further along Matemwe beach, the cement wall merges with one made out of coral.
The jagged rocks jutting out of the sand in front of it suggest that this is not the owner's first attempt.
"This is the third wall he has built, and it will last six months. The tides are now so strong that it becomes temporary," says Mr Kadogoh.
Further along, a property's boundary is marked out along the shoreline by the trunks of coconut trees driven deep into the sand.
Planks of wood have been nailed across them, joining them together.
This is the most successful defence, according to Mr Kadogoh.
As the waves crash against the poles, the planks weaken their force and do not allow them to dredge the sand back to sea.
The problem with building defences is that they must run along an entire beach to be effective.
And to protect a boundary of 20 metres using coconut poles, costs between $500 and $600.
The sea's mercy
Most beach-front plots are now owned by foreigners, so residents of Matemwe village depend on them for their protection.
Haji Mkali Pili, a teacher at Matemwe School, says the village itself only opens up onto small areas of the shoreline.
And he says even these parts are too expensive for villagers to defend.
Another villager, Haji Khamisi Musa, believes mangroves are the answer.
"The roots of the mangrove trees extend like fingers, and grab hold of the land so it is not swept away. Where mangroves exist, the land holds," he says.
For Mr Pili, who feels such local defence attempts are futile, there is only one solution when your home is at the mercy from the sea.
"If the sea comes, move up further up from the beach. No problem," he says.
For the moment, he sees no urgency, but realises that Matemwe villagers should probably start moving further inland quickly before the land is snapped up by wealthy Zanzibaris in search of a second home.
With a new tarmac road being built in the area and electricity becoming available, he says: "Clever people from town are already spending millions of Tanzanian shillings to buy and build there".
