A Big Island family that wants to preserve the rural character of the Hāmākua Coast has donated a conservation easement on 4,500 acres of its property to The Nature Conservancy.

David and Josephine DeLuz have owned and operated the 10,200-acre Kūka'iau Ranch for the past 15 years. But the DeLuzes, who are nearing 80, said they were concerned about what might happen to their ranch once they pass on.

Under terms of the agreement, negotiated with The Nature Conservancy and the Hawai'i Island Land Trust, the DeLuzes will retain ownership of the land and the conservancy will monitor and enforce the easement, according to a news release from The Nature Conservancy.

"We realized that if we didn't move to protect the ranch now, it could be divided up and sold off for development," David DeLuz said. "And then it wouldn't be a ranch anymore. It would be a residential area."

Kūka'iau's agricultural zoning allows the ranch to be divided up into 40-acre lots and sold, with one house built on each lot. By placing a conservation easement on 4,500 acres, the DeLuzes have ensured the land can never be broken up and developed, even if it is eventually sold.

It's the first step in their larger vision to use conservation easements to protect the entire 10,200-acre property.

"Kūka'iau is a historic ranch," Josephine DeLuz said. "It's been a fixture on the Hāmākua Coast for more than 125 years. It's a place that should be conserved."

John Henshaw, the conservancy's director of conservation programs, said the 4,500-acre easement covers the uppermost portions of the ranch, which rise to 8,400 feet in elevation and have the greatest conservation value.

About one-quarter of the lands under easement will be managed strictly for conservation, he said. The remainder will be restricted to sustainable agriculture and forestry activities, with no residential development.

Kūka'iau Ranch was founded in 1883 and remains one of the Islands' oldest working ranches. Historically, it was one of the most diversified and sustainable ranches in the state, and included a feedlot, meat processing facility, dairy and orchards, according to The Nature Conservancy.

Over the past century, however, unsustainable tree harvesting, numerous fires and continuous grazing have caused erosion problems, loss of stream flow and destruction of native plant seedlings, The Nature Conservancy said. As a result, its established-forest land is now less than 2,500 acres, and invasive species put the remaining Kūka'iau ecosystem at risk.

The DeLuzes' vision is to return the ranch to its former productivity and protect areas of historic and ecological value.

"The family's goal is to prove that working ranches can be profitable agricultural centers, while at the same time providing protection of watershed, species and cultural resources," Josephine DeLuz said.

In the coming year, the DeLuzes will work with the conservancy, Hawai'i Island Land Trust and the Natural Resources Conservation Ser-vice to develop a management plan that will guide conservation and reforestation efforts on the ranch.

That plan will likely include fencing, removal of pigs and goats, and restoration of native plant species.