The vast Hawaiian wetlands have largely been destroyed during the past two centuries.

They've been drained for agriculture, like the vast Mana plain on Kaua'i, where great flocks of wetland birds once lived and where Hawaiians traveled the region by canoe.

And they've been converted for development, like what's now Hawai'i Kai.

And dredged to form maritime facilities, like what's now Pearl Harbor.

Some have simply silted in over time, and others dried up because the streams that once kept them wet have been diverted to other uses.

A few survive, and the U.S. Fish and Wildlife Service, recognizing their value, particularly to waterbirds, is funding projects on three islands to enhance them.

As part of an $18.8 million National Coastal Wetlands Program, the Hawai'i projects will get $2.4 million, to be matched by more than $3.3 million in funds from conservation groups, private landowners and the state. Each of the projects is being handled by the state Department of Land and Natural Resources.

At Kaua'i's Mana Plain Coastal Wetlands, the land department, which has already created a collection of ponds for waterbirds, will create a new 141-acre stretch of wetland, dune and coastal strand. Although the region is still being pumped to keep it dry enough for agriculture, the state has found that if it digs a few feet below ground level, it hits water and can create waterbird habitat. A number of waterbirds take advantage of the new wetlands, including the koloa, or Hawaiian duck.

At Pearl Harbor, the department will restore 40 acres of degraded wetland at Pouhala Marsh. The wetland in the region has been invaded by mangroves and other weeds, making it less useful to the four endangered Hawaiian waterbirds. In all, Pouhala has 70 acres and is described by the Fish and Wildlife Service as "the largest remnant of what was once an extensive system of wetlands in Pearl Harbor."

On Maui, the state plans to use the wetlands funds to buy the 78-acre Nu'u Makai Wetland Reserve on the island's southeast shore. The land includes close to a mile of coastline. The wetland region is used by three Hawaiian waterbirds, and endangered Hawaiian monk seals haul out on the shoreline.

Some of the work in the wetlands will include the planting of coastal wetland plant species.

The four endangered Hawaiian waterbirds are the koloa; the 'alae 'ula, or Hawaiian gallinule; the 'alae ke'o-ke'o, or Hawaiian coot; and the ae'o, or Hawaiian stilt.

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.