Thakeham Homes has put forward proposals for the new houses on land at Buck Barn, West Grinstead.
But huge public opposition has been voiced - along with objections from the nearby Knepp Estate that fears the development would be detrimental to its world-renowned rewilding project.
However Thakeham Homes says that its planned new green bridge will enable wildlife to move freely in the area.
It says it will be ‘the biggest single biodiversity project in the county’s history.’
The bridge is designed to span four lanes of the A24 with the £5million cost being met by Thakeham as a ‘gift’ to the new community it wants to create at Buck Barn called Wealdcross.
A Thakeham Homes spokesman said: “The bridge joins land that has been isolated by the A24 and provides a safe route for wildlife in Buck Barn and surrounding areas to connect.
“When built, the strategic vision to create a connected biodiversity corridor from Climping in the south to St Leonard’s in the north will be one step closer to reality.
“The green bridge follows an iconic hourglass, or parabolic, shape to create a natural funnel for wildlife.
“The bridge is inspired by the A21 Scotney Bridge in Kent and draws on design and landscaping insights of ecoducts in the Netherlands.”
The developers say that the northern boundary of Wealdcross has been designed to act as an ecological buffer, screening wildlife corridors from any disturbances, including separation from pedestrians, cats, and dogs.
The continuous green infrastructure would also shelter the wildlife corridors from light, noise, and air pollution, as well as containing native species beneficial to pollinators, says the company.
Thakeham chief executive Rob Boughton said: “The bridge has the potential to transform the ecological future of the area for generations to come.
“We know how deeply people care about local wildlife.
“We have read and listened to the debate. One issue was clear: the A24 is an artificial barrier blocking wildlife access between the rewilding at Knepp Estate and the farmland beyond it.
“When the A24 was built, little thought was given to how the road might fragment wildlife and affect biodiversity. But, today, our priorities are very different.
“This is our opportunity to put it right. The Knepp Estate is now a biodiversity hotspot; full of species that are longing to break out into the wider countryside.
“The green bridge, plus northern edge ecological buffer with no-pedestrian access, will facilitate a better and more sustainable future for plants, birds, insects and wild animals in the area.
“Sussex is blessed with a rich mosaic of habitats across the county, many rightly protected as Areas of Outstanding Natural Beauty or Sites of Specific Scientific Interest. But the land at Buck Barn has no such challenges.
“That means that whilst meeting nature’s needs, we can also meet the needs of local people in Horsham district.
“We can ease the burden on local schooling. We can invest in and enhance local infrastructure. We can create a new community for all.”
The company says that more discussions with landowners and local residents are planned.
And, it says, the final green bridge design will be submitted as part of its overall plans for the area which will include new hedgerows to act as biodiversity corridors connecting areas.
Thakeham head of sustainability Josie Thornewill said: “We need biodiversity corridors to connect fragmented habitats. We need more of them.
“They need to be bigger, better and more joined to provide wider ecosystem services like pollination and wild species diversity.
“Corridors provide routes for wildlife from dragonflies to deer to move, expand, and adjust to change.
“Green bridges are a great solution. But the UK is lagging behind. We only have a small number in Britain whilst Europe and North America recognised the importance of them long ago.
“Wealdcross and Sussex can lead the way. We hope other developers will be inspired to follow our lead too.
“We believe that in years to come, future generations will acknowledge the part played by Wealdcross in showing the wider world how sustainable communities and wildlife can thrive together.”
The final wildlife bridge designs will be included with plans submitted to Horsham Council for the whole 3,500-home development which also includes plans for road improvements, a new secondary school, two new primary schools, a local health centre and a new indoor sports hall with mixed use 3G/4G pitches.