Richard Matsumoto was shocked to see the lush green Kalihi Valley being attacked by invasive plants just a few miles from his high school campus.

“;I didn't know we were so overridden with this kind of stuff,”; the Farrington High senior said about a visit to the valley earlier in the semester. “;When we pulled out all those invasive species, pretty much nothing was left.”;

Matsumoto and seven students who joined the cleanup in Kalihi and a similar effort in a Kaneohe gulch have been awarded $10,000 as winners of a national environmental competition. The students each earned $875, with $1,000 going to their adviser, physics and chemistry teacher Bebi Davis, and $2,000 to their school.

The team, Protect the Aina, designed T-shirts, documented excursions with videos and photographs, and posted information on a Web site and on social networking sites as part of the Lexus Environmental Challenge. The students passed out hundreds of fliers to raise awareness about invasive species' threat to Hawaii, which they learned has implications for the islands' fragile ecosystem and the state's tourism-based economy.

“;Visitors come to the islands and are able to see Hawaii's beautiful sites, ranging from our mountains to tropical forests to parks and many other places,”; they wrote in a 17-page report. “;All these sites vary in diversity. However, many of Hawaii's native plant species are either endangered or at risk of becoming endangered.”;

The team was one of 16 nationwide that clinched the first phase - with the topic being land - of the Lexus contest and advanced to the finals next year. Forty-eight teams will compete for grand prizes next year once the challenge's two other stages - water and air - are completed.

To finish their project in six weeks, the Farrington High students worked in the afternoons, on weekends and during the fall break. On one school night they met at Davis' home until 10 p.m. to edit their paper and, eventually, eat a dinner the group also helped prepare. While in the field, they learned to harvest invasive species and let them dry in the sun so their roots will not find the ground again.

Joyce Aquino, who wants to go to medical school, said she enjoyed mud-sliding and laughing at a friend who got stuck in knee-high mud. Aquino said she is worried that valuable plants with possible lifesaving medicinal qualities could perish.

“;As we lose the native species, we also lose some chances of finding some new cures for something,”; she said.

Davis and her students might tackle wind turbine technology or study a house powered by renewable energy for their finals entry. The team's other members are Elvis Grande, Minh Trang Nguyen, Nadine Pilande, Jorge Portillo, Daniel Remigio and Travis Takashima.

Earlier this year, Davis, who was selected Hawaii's Teacher of the Year in October, and other Farrington High students took one of two grand prizes from the previous Lexus challenge. They shared $75,000 for a campaign to educate people about the benefits of clean energy such as fuel cells.