The Big Question: Why is the RSPB paying £12m to flood prime farmland on the Essex coast?

Why are we asking this now?

The Royal Society for the Protection of Birds has announced that it intends to spend £12m on buying and then flooding Wallasea Island in Essex to recreate one of Europe's largest coastal wetlands. The 736-hectare site is two and a half times the size of the City of London and it will become a magnet for the many water birds that are having an increasingly hard time because of the loss of their natural habitats of saltmarshes and mudflats, the society says. The Wallasea Island Wild Coast Project will be the most ambitious and costly programme that the bird charity has ever instigated. It is also one of the largest coastal flooding projects in Europe.

Why does the RSPB want to do this?

Essentially because the opportunity arose. The private farming company that owns the island put the land up for sale and the RSPB saw that it would be possible to buy it outright and turn it back into its natural state. The charity says that 400 years ago there were about 30,000 hectares of inter-tidal saltmarshes around the Essex coast, whereas today the figures stands at just 2,500 hectares – and it's declining at the rate of 100 hectares a year. Buying Wallasea Island and turning it back into mudflats and saltmarshes is an attempt to redress the balance in favour of the wild birds that need this sort of watery habitat for breeding and feeding.

Has this sort of thing been tried before?

Yes, but on a much smaller scale. Freiston Shore, an RSPB managed nature reserve near The Wash, for instance, was created by deliberately flooding coastal land. It is now a developing bird reserve with an expanding range of wetland habitats. The reserve is the most important site in Britain for wintering birds, with over a third of a million wildfowl and wading birds present during the winter.

So will the RSPB just let Wallasea Island flood naturally?

It's not quite as simple as that. Before any of the sea defences are deliberately breached, the society will carry out extensive surveys and hydrological studies to try to gauge the effect of any flooding. That will cost about £500,000. But within five years it is hoped that much of the island will be allowed to flood naturally with the tide. Within 10 years, the RSPB believes that the island will have reverted almost completely to the state it was in before draining began more than 400 years ago.

How would the island change in 10 years?

At the moment, the island is a highly managed, single plot of land and is covered in fields that are very regular. Once the re-flooding scheme is finished, the island will be split into about five different segments of land which will become inundated with water channels, marshes and other types of semi-aquatic habitat ideal for birdlife.

In the words of the Royal Society for the Protection of Birds: "Our vision for Wallasea Island is to turn the blank canvas of arable farmland into a rich mosaic of habitats with approximately 320 hectares of mudflats, 160 hectares of saltmarsh, 96 hectares of shallow saline lagoons, 64 hectares of brackish grazing marsh and 129 hectares of pasture."

Isn't it a lot of money to spend on flooding prime farmland?

In fact the price of the land is believed to be around £5m. The rest of the £12m will be spent on research studies and the engineering work that needs to be done to allow the saltmarshes to regenerate slowly and safely. However, the RSPB believes that the price is well worth it in terms of recreating the natural habitats for wild birds that have disappeared rapidly in Britain over the past 100 years.

As Graham Wynne, the RSPB's chief executive, said: "Wallasea will become a wonderful coastal wetland full of wildlife in a unique and special landscape. It will be a supermarket for birds, create nursery grounds for fish and be a true wilderness that people can visit, savour and enjoy."

What sort of wildlife will benefit – and will the public be able to enjoy the sight?

The RSPB believes that the shear size of the regeneration will bring in many new species and boost the populations of existing species. Three species of water birds in particular are being targeted: spoonbills, which currently nest in Holland, the blackwinged stilt, which has only bred a couple of times in Britain, and the Kentish plover, which used to breed here until the 1950s when it disappeared because of the loss of its nesting habitat.

The RSPB insists that the new site will be a landscape used by people as well as birds. It says it will improve access to the site wherever possible so that wildlife enthusiasts will be able to savour the joys of seeing a large wetland habitat as it would have looked more than 500 years ago.

Don't rising sea levels mean that this is the wrong time to be flooding the coast?

The RSPB see this project as an example of how to adapt to climate change. At some point in the near future the sea defences around Wallasea will become uneconomical to defend any further. So it makes sense to make the necessary adaptation now and at the same time recreate the natural habitats for water fowl and other wetland species.

The north coast of Wallasea is already incorporated into a scheme to allow the planned tidal inundation of the land as part of an earlier wetland-restoration project. Mark Avery, the society's conservation director, said: "Our plans for Wallasea reflect the very great difficulties that climate change will cause but also the RSPB's determination to find ways of combating them. We will be providing new sites into which wildlife can move when sea level rise swallows up their existing habitats."

Can anything stop this project?

Yes. Money is still needed. The RSPB effectively needs to collect all the £12m within the next two years, and only a fraction of the sum is believed to have been secured. This is why it has launched an appeal to the public to help it collect the missing millions and put the scheme into effect. The society believes that if the money is in place there is nothing that can stop it from recreating the sort of habitat that existed in the days of King Canute – who is said to have claimed the island as part of his kingdom.

So should we deliberately flood a stretch of Britain's coast?

Yes...

* It will create a valuable bird reserve and important wildlife refuge for other species

* The land now is highly managed and is not a good habitat for wildlife

* The sea will eventually reclaim the land so we should do it now rather than later

No...

* Why flood something now that will flood naturally in the coming decades?

* The £12m that the project will cost could be better spent elsewhere on nature conservation projects

* We need all the agricultural land we can get in times of impending food shortages