Alexander & Baldwin Inc. has agreed to turn over management of 7,050 acres of remote Kaua'i land to The Nature Conservancy, creating the state's third-largest private nature preserve.

The largest private preserve is Maui Land & Pine's 9,881-acre Pu'u Kukui Preserve, followed by the Nature Conservancy's 8,061-acre Kona Hema Preserve on the Big Island.

The latest agreement, which covers an area above Ha'ena on the island's windward coast, is for a period of 10 years. The A&B Foundation has also made a $100,000 grant to the Nature Conservancy for conservation and outreach programs.

The Nature Conservancy's management agreement covers about 5,750 acres of Wainiha Valley and nearly 1,300 acres of the Alaka'i plateau and Mount Wai'ale'ale summit region.

Wainiha is home to 127 species of flowering plants found only in Hawai'i, 41 of which are found only on Kaua'i, according to the Nature Conservancy. Wainiha contains numerous species of native forest birds, including 'elepaio, 'apapane, 'amakihi and the rare 'akikiki and akeke'e.

"Wainiha is a place of incredible natural beauty and a treasure chest of Hawai'i's native plants and animals," said Suzanne Case, the Conservancy's Hawai'i executive director. "It's been our highest priority for conservation for many years. Now, thanks to Alexander & Baldwin, we will be able to protect it. We are deeply grateful."

The land to be managed by the Nature Conservancy is part of about 10,000 acres owned by A&B in the Wainiha Valley area.

"A&B has been a dedicated steward of these Kaua'i lands for well over a century, and over time, our awareness has sharpened about the tremendous biological importance of this valley and the imminent threats to the habitat," said Alexander & Baldwin Chairman and CEO Allen Doane.

The Nature Conservancy signed its agreement with A&B in April. However, the agreement did not take effect until last Friday when the Board of Land and Natural Resources terminated a prior surrender agreement between the state and the landowner.

The state had managed the land under various agreements dating back to 1948.