Some years ago, then state forester Michael Buck considered using cattle for conservation — a shocking idea to folks in the conservation community who viewed cattle as one of the causes of the destruction of native forests.

But Buck recognized that the browsing of cattle could knock back invasive weeds faster and less expensively than human crews, if you managed them carefully and removed them before they started doing more damage than good. The idea never got much traction.

The Nature Conservancy of Hawai'i is using another unusual tool for conservation: the bulldozer, normally viewed as a symbol of development — to many the antithesis of conservation.

"You'd never expect that our most important conservation tool would be a bulldozer, but it is," said Rob Shallenberger, Hawai'i Island programs director for the Conservancy.

At its Kona Hema Preserve, manager Mel Johansen, a bulldozer operator and mechanic, suggested the strategy, and the conservancy picked up a used Caterpillar D5.

Johansen uses it to build fences that keep pigs and sheep out of native forest, to repair roads, cut firebreaks, prepare the ground for planting of native species, and to rough up the surface so koa seeds will sprout, a process called scarification.

"We have scarified more than 200 acres so far at a rate of five to 10 acres per day," Johansen said. Koa seeds respond quickly to sunlight, and some of last year's koa seedlings are already more than 10 feet tall, he said.

The use of heavy equipment wouldn't be permitted in conservation-zoned land, but Kona Hema is in the state's agricultural zone.

"Our goals here are not just to protect what we have, but to demonstrate that forest recovery is possible. With the right mix of techniques — fencing and the removal of pigs and sheep, fire protection and the scarification of soil, we will see the forest recover," Shallenberger said.

The 8,000-acre Kona Hema preserve, in South Kona on the slopes of Mauna Loa, is made up of three adjacent parcels of land acquired by the Conservancy since 1999 at Honomalino, Kapu'a and Papa. The preserve lies next to the state's Manuka Natural Area Reserve.

The property is upland native forest, ranging from about 3,000 feet to more than a mile in elevation. It contains numerous native plant and animal species, but has been affected by koa harvesting and grazing by cattle and other herbivore.

If you have a question or concern about the Hawaiian environment, drop a note to Jan TenBruggencate at P.O. Box 524, Lihu'e, HI 96766 or jant@honoluluadvertiser.com. Or call him at (808) 245-3074.