Already at the forefront of environmental activism within the music business, Jack Johnson is stepping up his efforts on his summer tour, which begins June 13 outside Indianapolis.

The artist, who is in his third week at No. 1 on The Billboard 200 with the album "Sleep Through the Static," is launching the All At Once online community in conjunction with the tour. Fans can visit the site to learn about environmental causes and sign up to carpool to shows.

When tickets go on sale March 15, fans can choose to pay an extra $1.50 fee to offset carbon emissions associated with traveling from the show. Offset "stickers" will also be sold at venues.

Johnson's tour, which wraps Aug. 24 at San Francisco's new Outside Lands festival, will feature support from acts on his own Brushfire label such as Rogue Wave, Neil Halsted, Mason Jennings and Money Mark.

Here are Jack Johnson's tour dates:

June 13: Noblesville, Ind. (Verizon Wireless Music Center)
June 15: Manchester, Tenn. (Bonnaroo)
June 17: Cuyahoga Falls, Ohio (Blossom Music Center)
June 18: Clarkston, Mich. (DTE Energy Music Theatre)
June 21: East Troy, Wis. (Alpine Valley)
June 22: Somsert, Wis. (River's Edge)
Aug. 3: Oro, Ontario (Burl's Creek Park)
Aug. 6: Mansfield, Mass. (Tweeter Center)
Aug. 7: Camden, N.J. (Susquehanna Bank Center)
Aug. 10: Jersey City, N.J. (All Points West Festival)
Aug. 12: Raleigh, N.C. (Walnut Creek)
Aug. 13: Atlanta (Lakewood Amphitheatre)
Aug. 15: Bonner Springs, Kan. (Sandstone Amphitheatre)
Aug. 17: Morrison, Colo. (Red Rocks)
Aug. 18: Salt Lake City (USANA Amphitheatre)
Aug. 20: St. Helens, Ore. (Columbia Meadows)
Aug. 21: Vancouver (Thunderbird Stadium)
Aug. 22: George, Wash. (the Gorge)
Aug. 24: San Francisco (Outside Lands Festival)