With the snow finally clearing and summer vacation nearing, the call of the wild is sounding more strongly. But are children and teenagers hearing it?

Former Hopkins science teacher and school district naturalist Larry Wade believes that once they get outdoors, young people will find plenty of reasons to keep exploring. He's written a book designed to inspire such curiosity and discovery.

"There's a whole generation of Americans now that aren't getting out enough to experience the outdoors," he said on a hike through Lone Lake Park in Minnetonka on a recent humid, overcast spring day. "It's such a busy world that we live in. If people just slow down a bit and spend some time out here, they can really get a lot of juice from it."

Wade, 65, retired last June after 19 years of working for the Hopkins School District, the first eight as district naturalist and the last 11 as a sixth-grade science teacher at Gatewood Elementary.

In the time he gained this year, he completed his third book, "The Nature Seeker Workbook: Connecting to the Wilds of Your Neighborhood." The book lays out more than 50 seasonal outdoor activities designed to get parents and teachers to spend more time outdoors with kids. It also contains hundreds of illustrations and diagrams by local artist Jeanette Dickinson and Boston-based Amelia Ladd. The book can be purchased at The Old Naturalist website, Fort Snelling State Park and the Minnesota Valley Wildlife Refuge.

During the hike, Wade stopped frequently to point out and identify the ­myriad sounds of nature along the shoreline of Lone Lake.

Chorus frogs led the cacophony with their endless, rolling beeping. And now and then, Wade would point out the low, snoring call of the leopard frog.

Nearby, a blue jay chirped its "pump-handle call," which sounds exactly like a creaky pump handle and is heard only in the spring. Later, a male downy woodpecker could be heard hammering its spring mating drum on a maple tree.

Spring is Wade's favorite season. He also loves fall, he said, but he finds Minnesota summers to be too hot (despite being a native of Southern California) and its winters beautiful but desolate.

The "Nature Seeker Workbook" breaks down into four sections, one for each season, with points awarded for each activity completed. Wade acknowledges that he uses the lure of competition to get kids outdoors, but he said once they get out on the trail, Mother Nature usually takes care of the rest.

A few years ago, he was leading a hike through another park right after a massive damselfly hatch. Damselflies are similar to dragonflies, but have a slightly different anatomy and are generally smaller and weaker fliers.

"I was walking with these little fourth-grade kids, and damselflies are everywhere, landing all over them, and they were in absolute awe, just like, 'whoa,'" said Wade with a laugh. "Events like that stick with them. Kids will remember that stuff for the rest of their lives."

The wild as doctor, teacher

According to a 2012 report issued by the Centers for Disease Control and Prevention in Atlanta, when a survey of Minnesota high school seniors asked, "On how many of the last seven days were you physically active for a combined total of at least 30 minutes," 49 percent of boys and 67 percent of girls reported that they had not participated in physical activities for five or more days per week. There are repercussions: Seden­tary habits students developed during childhood contribute to 62.3 percent of adult Minnesotans being classified as overweight, according to the same report.

Some studies have shown that spending time outdoors can boost physical and mental health in other ways as well. A 2004 study published by the University of Illinois found that "exposure to ordinary natural settings in the course of common after-school and weekend activities may be widely effective in reducing attention deficit symptoms in children."

The long-term benefits of spending time outdoors (and the negative impacts of not engaging in nature) are explored further in Richard Louv's 2004 bestseller, "Last Child in the Woods," in which Louv coined the term "nature deficit disorder" to describe the harmful effects of American children's decreased exposure to the outdoors.

The joy of outdoors discovery

As Wade walked, he talked about how he teaches students to calculate the age of a tree (the circumference of a tree 4.5 feet from the ground divided by pi, then multiplied by the tree's growth factor, which he has a chart for in his book) when he spotted a big, teepee-style fort made from old branches and logs, deep in the forest.

He abruptly stopped and tromped into the underbrush to get a better look.

"Oh gosh, that's awesome; that's what kids should be doing," said Wade. "That's a really fine-looking fort." In fact, page 50 of "Nature Seeker Workbook" addresses "The Importance of Forts."

"The average kid that lives in downtown Hopkins probably won't get out and do something like that, and it's a shame, because that's a great, long-term fort. Built to last," Wade said.

His genuine fascination with the outdoors remains almost childlike after many years as an outdoor educator.

Ceaseless curiosity and alertness emanate from his blue eyes, allowing for a lot of discoveries like the fort. During the hike, he dropped a lecture mid-sentence to follow a muskrat swimming along the shore and returned to point out a hole in a tree that housed a raccoon, which led to another discussion on animal dwellings.

Wade said he's far from finished as a naturalist. Next year he hopes the Hopkins School District will adopt a natural-science program he has developed, and described his book as "only one of many threads I've begun to pull on."

Then he saw his first bumblebee of the year — "That's a big one, probably a queen" — and off he went, down the trail.

Ben Johnson • 612-673-4499