Council officers are investigating after protected trees at a beauty spot were bulldozed.
The land at Cragg Hill Road in Thackley, a former railway, had become an area of wildlife and natural beauty over the last 12 years.
But people who live nearby have protested about the destruction of the trees and believe the site, which had become a haven for foxes, owls and bats, is being prepared for a housing development.
A Bradford Council spokesman confirmed that the land owner, who is understood to live in Leicestershire, had breached a tree preservation order, and six trees - five sycamores and one ash, all aged up to 40 years - had been destroyed.
An investigation was under way and appropriate action would be taken, he added.
Jill Brearley, of Leeds Road, whose house overlooks the area, said: "It's an area of local beauty used by people to walk their dogs and for children to play. But now it is just a big heap of earth and mud.
"We know that the owner has the right to do what he wants with his own land but he has breached a tree preservation order.
"If I have to abide by the law then so must he. But when I spoke to him he was very belligerent.
"When we moved to this house three years ago it was a place where our children could play and it was part and parcel of us buying the house. Now we are trying to save the area because we live here and must have a say."
Councillor Jeanette Sunderland, the leader of the Council's Liberal Democrats group, who is investigating the situation on the residents' behalf, said the owner had not applied for planning permission to build on the land.
She said: "He's destroyed trees and hedges but given no indication of what he intends to do with the area because he has not applied for planning permission and it is causing anxiety among the residents.
"He has also left the area unsafe with massive drops between the roadside and the area. The bottom line is that residents can report damage to the highways but he is entitled to move earth because it is his site.
"When he does apply for planning permission, the residents can then voice any concerns."
A spokesman for the Council's planning department confirmed it had not yet received any planning applications for the site.
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