Mark White, Maui program director for The Nature Conservancy, said he could hardly believe the results of a survey of native trees and shrubs in the Waikamoi Preserve on Haleakala's north slope.

In some cases, native plants have recovered by 300 percent or more since goats and pigs were fenced out of the area, according to the survey done last year by Guy D. Hughes III, a plant ecologist with the Kalaupapa National Historical Park on Molokai.

“;We were super-excited about it,”; White said in an interview.

Goats and pigs had ravaged the Waikamoi Preserve area for 100 years. White said hunting wasn't enough to make a difference in the population, with breeding rates high.

“;We got the last goat out in 1994 and the last few pigs out about the same time,”; he said. “;Pigs can rototill a lot of area in a single day.”;

Hughes did a survey in 1994 showing upper subalpine areas were open and dominated by native and alien grasses. His survey last year showed a three-fold increase in native cover and a 50 percent reduction in dominant alien grass, White said.

Recovery was expected but the nonprofit environmental group was “;amazed”; how much had occurred by the 2008 survey, which demonstrates the importance of protecting native forests and watersheds from invasive animals, White said.

  The survey covered the area running north from near Hana Mountain or Hanakauhi peak—1,000 acres between the 6,000 and 8,600-foot elevations. It is a very remote area, rarely visited, White said.

The preserve includes 5,230 acres in the East Maui watershed, with 63 species of rare plants and 13 kinds of native birds, the conservancy said.

“;The neat thing,”; White said, “;is this (recovery) is at the top of the watersheds where we get the most erosion on steeper terrain. It is a big benefit for the watershed. What was really amazing, too, is the recovery happened in one of the driest periods on record in the last 15 years.”;