Tourism is a $5 billion proposition in New Hampshire — the state’s second largest industry. And much of the attraction is the abundance of mountain trails, rivers and streams that make the state a beautiful destination.

The state’s tourism website promotes kayaking, mountain biking, ATV riding and more, all of which rely on clean rivers and clear trails. And who keeps our rivers and trails safe and free of debris?

The state Division of Forests and Lands does offer help in forest stewardship, through the UNH Cooperative Extension, but the actual work of keeping trails and other recreational areas clear and safe largely falls to volunteers.

Many such efforts are coordinated through the Society for the Protection of N.H. Forests, such as this week’s Monadnock Trails Week. Beginning Monday, volunteers are spending the week improving trails all over the region’s namesake mountain.

“We could not keep Mount Monadnock safe for hikers without the volunteers that come out to help maintain the trails every year,” said Dave Anderson, senior director of education for the Forest Society.

Trail safety is a key to keeping Monadnock the most-hiked mountain in the country — arguably the world. During good weather, nary a week goes by that someone isn’t carried down the mountain with a leg injury or other ailment. But that’s not for lack of effort on the part of those who brave the heat, humidity, bugs and grime to keep the trails in good condition.

And that’s just Monadnock State Park. The Friends of Pisgah perform the same service regularly in the region’s largest state park, while others volunteer to maintain smaller venues, such as Goose Pond, Rhododendron State Park or Pack Monadnock.

As for those looking to take a dip or ride upon the water, there are similar efforts annually in which volunteers slip on their most-disposable clothes and literally wade into the job of hauling shopping carriages, bicycles and more out of our rivers and streams. The Source to Sea cleanup is a major event, this year slated for Sept. 27 and 28. The event is organized by the Connecticut River Conservancy, but that river is only a part of it: Locals also take to the Ashuelot River and Beaver Brook in Keene, which eventually feed into the Connecticut.

Don’t think these events are limited to the summer and early autumn, though. An array of snowmobile clubs groom and maintain trails throughout the winter months.

Not all of these efforts are altruistic attempts to benefit tourists. Many of those who spend hours maintaining trails or cleaning up rivers do so because they use those areas themselves. But the result is the same: cleaner, safer avenues for taking advantage of the woods, mountains and streams that make this region so attractive for outdoor activities.

So consider helping out. And to those who already do so: nice work.