Councillors refused permission for Avant Homes to build 71 properties on Owlthorpe Fields at Moorthorpe Way, Crystal Peaks, in South Yorkshire but they were overruled by a planning inspector.
Known as Site E, it is one of three earmarked for development. Campaigners have now turned their attention to two neighbouring fields to try to save them.
In a silent protest, ribbons and drawings have been tied to metal fencing erected around the Avant Homes site.
Owlthorpe Fields Action Group says it empathises with the anger and resentment felt in the community but will work tirelessly to save Sites C and D.
The group is now liaising with Clive Betts MP, councillors, planning officers, Professor Ian Rotherham and Sheffield and Rotherham Wildlife Trust on how it can protect the other sites.
Christine Rippon, from the group, said: “Councillors voted overwhelmingly to reject the scheme last year and reluctantly, we have accepted that permission was granted by the planning inspector in March to allow building on Site E of Owlthorpe Fields
“It has been, and remains, a difficult time for our community. The erection of fencing has saddened and angered many local residents.
“Since permission was granted, the group has focused its efforts on saving two other areas of Owlthorpe Fields which remain unsold, sites C and D.
“We seek to protect them, and the Ancient Woodland of Ochre Dyke, during the excavation and development work of site E due to begin in September.
“In the longer term our aim is to save Sites C and D from future development. We believe they should be designated Local Wildlife Sites and for them to join the Wildlife Corridor which is being established in Waterthorpe, Beighton and Woodhouse Washlands.”
Ms Rippon said the group wanted to thank everyone for the positive discussions.
“The Declaration of a Nature Emergency passed by Sheffield Council has given us much hope that the issues of climate change and biodiversity loss are being addressed with passion and vigour.”