Around midday, when the sun is beating down from the clear Texas sky, 18-year-old Jonathon Jackson is swinging a hoe in the Great Trinity Forest. His leather gloves are worn. Tall trees partly block the sun, but they cannot erase the humidity.

The song of what seems like hundreds of cicadas fill the air as the South Oak Cliff High School senior yanks up grasses and plants to reach the dirt, which he then scrapes to make an even surface.

“We make it at least two lanes wide and as clear as possible and level and we just keep going until we finish,” he said. “Everything that is in the trail … we kind of move it off to the side, but we do not discard it. Because … we want to conserve everything and make it look natural.”

He stops for a moment, wiping the sweat from his face and grabbing a drink from a water bottle with the words “Student Conservation Association” printed on it. Then he starts hacking again at the woodland grasses.

Mr. Jackson is among a select group of 21 teenagers from 12 area high schools who are spending their summers improving local parks and nature preserves. Under the direction of the Student Conservation Association, the teens spend five weeks outside to create or renovate area nature trails as well as learn about conservation and the environment.

On the sixth week, the students will go on a camping trip – a first for several of them –

at Inks Lake State Park in Central Texas.

A nonprofit organization with programs around the country, SCA was founded in 1957 to restore and protect America’s public lands. Students who apply for the program must be recommended by a teacher or community member. SCA officials then interview applicants and choose a group for two summer crews of high school students. The Dallas SCA also offers internships for older students and is working on a year-round program for environmental education.

Youths in the summer high school program earn a stipend of $1,250 upon completion, paid in part with donations from groups such as The Meadows Foundation. Timberland, an outdoor gear company, donated the crew’s boots, while Darden Restaurants, parent company of Olive Garden and Red Lobster, provided a graduation meal and lunches for the students.

Mr. Jackson is helping clear 700 feet of trail each day in the Great Trinity Forest in South Dallas. Using an assortment of rakes and hoes, he and seven students and two adult crew leaders have cleared and leveled the ground for a two-mile loop that will open in summer 2009 as part of a 12-mile trail.

“I think you can do a lot of teaching in the classroom, but a lot of the teaching, when it is hands-on, you can get a lot more out of it,” SCA adult crew leader Megan Atkinson said.

The students also have learned about working outdoors and protecting North Texas’ natural habitats at the Cedar Ridge Preserve near Duncanville and The Heard Museum in McKinney.

The students assigned to Cedar Ridge built stairs on a rocky incline and cleared a trail of poison ivy, thorny brier and mulch chips.

“Greenbrier has little thorns all through there. It is really sharp,” said Eric Walker, 18, a Duncanville High School student who is spending his second summer with the SCA. “We did not want kids trying to grab on as they walk through. So we just wanted to throw it back away about an arm’s length back in there so they will not be grabbing it and hurting themselves.”

After about three weeks, the kids at Cedar Ridge wrapped up their work and moved to the Heard, where they were building a boardwalk, removing invasive plant species in prairie restoration and planting wetland grasses.

Students work on projects Tuesday through Friday. Mondays are environmental education days, when they learn about conservation and awareness on a local level. They have visited a high-performance green building, a wastewater treatment plant, and other natural locations to learn about the earth and proper environmental care.

The students’ knowledge is evident as they walk down the trails they’ve tended to for up to seven hours a day, identifying plant species and geological features.

Lakedrick King, 16, points out an area covered in Virginia creeper and talks about different species. He added that “Cedar Ridge” was probably not the best name for this park.

“There are really no cedars; most of those trees are junipers,” he said.

Although this is the first time many of these students are working outdoors, the SCA welcomes many returning faces, like Mr. Jackson. He started with the SCA in summer 2006 and came back last year. This summer, he is an apprentice crew leader, a student leader who is under 21.

“I chose the SCA because it was already in my nature. ... I was always in my own yard at home,” he said. “I liked coming outside and learning about different species that live outside. Some are Texas native plants and others are invasive species that are in Texas that we need to take out.”

Making the scenery look natural was harder at Cedar Ridge, where the team dug through layers of rock to put steps into a rocky slope. After fighting both water erosion and the tough rock, the SCA members finally set blocks of wood and rebar into the hillside to make the path easier to hike.

“Everybody we have seen that is walking out is saying, ‘Man, those steps look great. It used to be so slick and steep.’ And now they can just cruise right on down there, people jogging and everything,” Ms. Atkinson said. “SCA has been really great for all of us, I think.”