The preservation of Oahu’s shrinking agricultural resource is a core goal of land-use policy, for multiple reasons. The spatial aspect of open farm lands is important as a scenic element, especially given Oahu’s increasing urban density.

But the main reason, of course, is to preserve agriculture itself. Hawaii needs to become more self-sustaining in its food production, which means that, as much as possible, ag lands that remain should be put to productive agricultural use.

The same principle applies to the Dillingham Ranch, now proposed to be converted to an agricultural subdivision. The rules governing this use of agricultural lands must be strengthened to ensure it produces as farmland, and not just a getaway home for the well-heeled.

The 2,700-acre ranch is a particularly cherished property for its link to Hawaii history. Established in 1897, the home of the development and railway family is famous as a polo grounds and iconic gathering place for dignitaries and celebrities.

It’s no wonder that North Shore residents reacted with some chagrin at the first public presentation of the plan, which would convert about 934 acres into 91 agricultural lots of at least 5 acres each. The plan also includes an “agricultural cluster” of 15 “farm dwellings on two additional parcels.

City land-use regulations permit this on ag land, as long as the minimum, 5-acre lot size is met and as long as the dwelling and “not agricultural accessory uses” don’t exceed 5,000 square feet.

The developers also must submit, along with its subdivision application, a farm plan showing the feasibility of a revenue-producing operation. But implementation of the plan has not been enforced. As it stands, the ostensible “farmer” could decide not to pursue the agricultural plan.

Dillingham Ranch Aina LLC, a company based in Beverly Hills, is the applicant. Because the project proposes connections to Farrington Highway and a wastewater treatment plant serving the subdivision, the company was required to prepare an environmental assessment, now on file with the state Office of Environmental Quality Control.

The plan includes 13 lots with nonirrigated land for cattle grazing, 46 lots with irrigated pastures, 37 lots with orchard trees. The 15-home cluster would be arrayed on 125 acres, also designated for orchard trees.

It certainly sounds pastoral, with the additional proposed feature of a 22-acre artificial lake. Its function is described in the plan as a “scenic amenity,” not agricultural at all. Finally, the subdivision would have use of 15 acres surrounding the Dillingham house, which would continue to be rented out for events and lodging.

Very understandably, all of this drew fire from the North Shore Neighborhood Board, which voted 12-0 to recommend that the city Department of Planning and Permitting reject the subdivision applications. However, George Atta, DPP director, said as long as the basic requirements are met, the permit must be granted.

That may be true, but there must be a way administratively to improve on enforcement, ensuring that agricultural activities are conducted on the property. Otherwise, developers will be able to reap the benefits of an agricultural-zone property tax rate while essentially developing exclusive estates that ought to be taxed appropriately.

Various forms of commercial farming do exist, but the city must ensure that its 21st century “farmers” are performing that function, in some reasonable measure.