The Wildlife Trust has bought the land occupied by Godmanchester Nature Reserve thanks to a £90,000 grant.
A public appeal was launched last year to raise £60,000 towards the £400,000 needed to secure the Cow Lane site and maintain the former sand and gravel quarry as a wildlife haven.
The appeal followed the revelation that Cambridgeshire County Council was to propose a link road across the River Great Ouse near Cow Lane to relieve congestion between Huntingdon and St Ives.
More than 1,400 people signed a petition against the plan and the county council has since removed specific reference to the idea from its long-term transport strategy but has not ruled out reconsidering it in future.
Last month, the Bedfordshire, Cambridgeshire, Northamptonshire branch of the Wildlife Trust revealed it had secured the £90,000 from Viridor Credits through the Landfill Communities Fund, allowing it to buy the site from building materials supplier Lafarge.
Cambridgeshire reserves manager, Matt Hamilton, said: “This wonderful grant from Viridor allows us to finalise the planned purchase from the current owners and secure the reserve’s future.
“After two and half years of looking after the nature reserve at Godmanchester we have a good understanding of the wildlife and habitats, as well as forming a strong connection with the local people who visit and enjoy the reserve.
“We are delighted to formally acquire this key wildlife site at the heart of the Ouse Valley and will continue to build on the original restoration work.”
The reserve is made up of four lakes, formerly gravel pits, interspersed with grassland and ancient hedgerows.
The Trust has managed the site after award-winning work by Lafarge on restoring it over 40 years.
John Duffield, property estates manager for Lafarge, said: “We needed the right people to continue our work and were delighted the Wildlife Trust could take on the legacy.
“Recognising the tremendous work the Trust is doing in making the site an even better place for people to see nature, we have now completed the sale of the land to the Wildlife Trust. We wish the Trust well in their continued management of this wonderful site.”
INFORMATION: For more on the reserve, visit www.wildlifebcn.org/reserves/godmanchester.