A nature reserve near Lowestoft will be expanded following a successful Suffolk Wildlife Trust appeal to raise £1m.
Public donations will help fund the extension of Carlton Marshes, which will "transform the Broads" when completed in 2020.
The trust, which also received £4m lottery funding, plans to turn an extra 384 acres (155 hectares) into a wildlife haven.
Sir David Attenborough was among those who helped promote the project.
With a mixture of wetland, meadow and shallow pools, Carlton Marshes will be home to birds such as lapwing and bittern while a seven-mile network of freshwater ditches will allow plants, water voles and the rare fen raft spider to flourish.
A state-of-the-art visitor centre will also be created in a bid to encourage people to venture out into the Broadland landscape.
The energy-efficient building will include a cafe, shop, activity room and an outdoor play area for children.
Julian Roughton, chief executive of Suffolk Wildlife Trust, said: "The support for our vision for Carlton Marshes has been nothing short of spectacular.
"We knew when we started this campaign that £1m was an ambitious target, but the project is equally ambitious in that it will safeguard this precious piece of East Anglia for posterity.
"The fact so many people have recognised the importance of what we are trying to do, for both people and wildlife, really is very special."
At the time of the fundraising campaign's launch, Sir David Attenborough said the project presented a "unique opportunity" for wildlife.
"England's wildlife is under great and ever-growing pressure," he said.
"It is vital we restore our land on a landscape scale so it can support more wild plants and animals."