It’s only a few hundred yards from the canoe shed to the launch site, but the short distance traces a dramatic transition from woodlands to marshlands in Maryland’s Jug Bay Wetlands Sanctuary.

Red maple, green ash, and smooth alder trees taper to low scrubby shrubs before quickly turning into a medley of aquatic plants. Then, the blankets of green meet a sweeping river of blue. Perennials—heart-shaped spatterdock, arrow arum—poke through the shallows of the Patuxent River while higher stands of cattails, wild rice, and other water-loving plants extend from the banks. Red-winged blackbirds flit in and out, some breaking the silence with an “o-ka-leee” en route from reed to reed. Overhead, a bald eagle glides through a periwinkle sky, scouring the scenery for its latest prey. The rippling river extends north and south like outstretched arms, ready to embrace any living thing that enters. What better place to launch a canoe?

“It’s the best way to introduce someone to the sanctuary,” says Bill Steiner, who just wrapped up two years as president of the volunteer citizen support group Friends of Jug Bay. A couple of weekends a month, park naturalists and volunteers like Steiner lead canoe trips from the end of the Railroad Bed Trail. The outings immerse individuals, families, and scout groups into Jug Bay’s wetland ecology, helping them discover the area’s rich natural and human history.

The 1,250-acre Jug Bay Wetlands Sanctuary hugs the eastern shore of the Patuxent, where it makes a wide bend southeast of Upper Marlboro, Md. The sanctuary is Anne Arundel County’s largest park and marks the river’s midpoint—about fifty miles from both the headwaters at Mount Airy and the mouth at Solomons Island. Eight miles of trails and boardwalks meander through wetlands, woodlands, and vast open fields harboring two well-preserved tobacco barns.

“The diversity here is astounding, especially given our proximity to Washington,” says Chris Swarth, the sanctuary’s director. “Many of our visitors are quite surprised that you can leave the intense metropolitan area, travel east fifteen miles, and come to an area similar to what it was like 300 years ago.”

The sanctuary hosts one of the Chesapeake’s most productive habitats. More than 100 wetland plant species and 250 bird varieties have been recorded here, along with eight species of turtles, a half-dozen different snakes, a handful of frogs, and mammals ranging from river otter and beaver to red fox and white-tailed deer. To protect and preserve this environment, recreation is allowed by reservation only on Wednesday, Saturday, and Sunday. Other times, the sanctuary serves as an outdoor classroom for school groups and a field laboratory for researchers. “We strike a balance between limiting public access to preserve the sanctuary,” explains Swarth, “and designing and promoting educational programs to bring the public in so they can learn about wetlands and natural history.”

Out on the river, Steiner breaks from paddling to sidle up to a beaver lodge. The intricate pattern of branches and mud demonstrates the architectural genius of these forty-pound amphibious mammals. Just up the river, a much smaller pile of carefully constructed cattail stalks and other material signal other marsh residents: muskrats. Nearby, a bottle and assorted debris bobs in the water. “The marsh acts like a sieve,” says Steiner. “Much of what is dumped up river shows up here.”

The sanctuary’s tidal wetlands play a key role in purifying the Patuxent’s waters en route to the Chesapeake Bay. The tides, which transform the marshes from a mud zone to a flood zone every twelve hours, remove sediment and nutrients and trap pollutants. It is this rhythmic ebb and flow that makes the wetlands so productive.

To showcase the sanctuary’s critical role and location, Steiner paddles to the Prince George’s County bank of the river, to the Mt. Calvert historic site in Patuxent River Park. The colonial-era brick plantation home, perched on a rise, looks much as it did 200 years ago. And the miles-in-every-direction perspective from the hilltop illustrates why Native Americans (and later colonists) settled here. The sanctuary’s namesake, the half-mile-wide and mile-long Jug Bay, balloons to the south as the Patuxent River and its western branch bend east and north. Much of the land on both sides of the river is protected from development, making the area one of the Chesapeake’s largest tidal preserves.

Back in the canoes, Steiner is winding the trip to a close, as the persistent honking of Canada geese overhead turns the subject to the sanctuary’s native wild rice. This plant is an important food source for fall migratory birds—if the crop survives the spring. “The wild rice doesn’t have extensive roots,” Steiner explains. “Canada geese can pull out the whole plant when they feast early in the growth cycle of this annual, preventing it from ever producing seeds.”

To sustain these vital wetland plants, which can flourish to heights of twelve feet, the Friends of Jug Bay erected more than two miles of low fencing in 2003 to cordon off the wild rice plants. Keeping the invasive geese out of reach, these specially designed fences enable the roots to take hold. Thanks to the Friends’ hard work, Swarth reports that last year the wild rice had its strongest showing in a decade.

Every year, more than 300 people volunteer at Jug Bay. Half show up for single-day events, and the rest contribute their time on a regular basis, helping with research studies, environmental monitoring, and habitat protection. “We try to marry people’s interests with tasks that need to be done,” says Steiner, who’s been active with the volunteer group for nearly seven years.

Dave Linthicum, a dedicated volunteer for more than a decade, describes himself as “the keeper of Jug Bay’s geographical and historical trivia.” He enlightens us, for example, with the fact that the Patuxent River was the “superhighway of its day,” with 500-ton, 60-foot-long steamboats charting these waters throughout the 1800s. Today, the dozens of maps he’s created lead newcomers through every part of the preserve physically—and virtually—thanks to an interactive computer exhibit in the visitors’ center. He also leads canoe trips, cleans up trash, maintains trails, marks park boundaries, and more.

Diversity, he says, is the sanctuary’s appeal. “Most people are attracted right to the water, but there are miles and miles of trails,” he points out, noting that he recently spotted twenty-one wild turkeys on the Beech Trail, one of the least-hiked wooded trails. “The really easy way to miss Jug Bay is to come once, do a quick walk, and think you’ve experienced it. The folks who get the most out of it are the ones who join, become volunteers, and help out on a research project.”

Mike Quinlan, another Jug Bay Friend, has spent dozens of hours “in wet conditions” tracking the migration of marbled salamanders since 1998. He’s trapped and transported countless critters (400 in a single day!) to the visitors’ center for weighing, measuring, and photographing before returning them back home. “Because of the sanctuary’s amazing array of research projects,” he says, “volunteers have the chance to participate in an active way, and you don’t find that very many other places.”

Researchers come to Jug Bay to study everything from box turtles and earthworms to water quality and sedimentation. They hail from the likes of Johns Hopkins University, the Smithsonian Environmental Research Center, the Chesapeake Biological Lab, the University of Maryland, and the U.S. Fish and Wildlife Service. Last year sanctuary staff and volunteers installed hundreds of poles keyed to a Global Positioning System grid to allow researchers to pinpoint their location within the sanctuary, enabling more exacting research.

“It’s fairly unique that Jug Bay has the combination of recreational use and research,” says Linthicum, who designed a map plotting the locations of the poles. “But it’s really unique that it’s a county-owned-and-operated facility.” He notes that few counties nationwide devote so much effort to research—and have so many scientists seeking out their preserved land for studies.

“Citizens and politicians back in the late ‘70s recognized the value of wetlands and made a bold move to preserve this area—and to do it with local funding,” says director Swarth. “For the county to take over management of 330 acres of wetlands and forest with the intent of turning it into a nature preserve instead of a suburban park was a very unusual move,” he adds. “That first purchase was crucial. It allowed us to gain a reputation for conservation and stewardship, which allowed us to quadruple the land.”

And it’s still growing: The sanctuary just finalized the purchase of 305 acres of adjacent forest, farmland, and wetlands, and now protects nearly two-and-a-half miles of contiguous Patuxent shoreline. “It’s only by acting today, that we can guarantee what the future’s going to be like,” says Steiner, who advocated the purchase as president of the Friends. “I’m a real believer in purchasing these areas. They become the legacy we leave for our kids.”

Karen-Lee Ryan, a Washington-D.C.-based freelance writer, saw three deer, a black rat snake, a muskrat, and countless ducks and birds on her first trip to Jug Bay Wetlands Sanctuary.

Jug Bay Wetlands Sanctuary

1361 Wrighton Rd., Lothian, Md. 20711, 410-741-9330, http://www.jugbay.org.

Times: Open to the public Mar.-Nov., by reservation 9 a.m.-5 p.m. on Wednesdays, Saturdays, and Sundays.

Admission: $3 for adults, $2 for seniors & those under 18. Friends of Jug Bay members free. (Friends’ dues are $12 per person & $20 per family.)

Exhibits: Interactive exhibits at the Visitors’ Center detail the wetlands’ role in purifying water and introduces the animal and plant residents by telltale clues.

Canoe Trips: Four-hour, guided “Marsh Ecology by Canoe” trips run most weekends. Open to those age 7 and up. $5 per person. Reservations required. Canoe instruction and all equipment is provided. Canoe rentals for groups only available in the sanctuary.

Volunteer Opportunities: Fill out an application for regular stints (available at jugbay.org). They’ll pair your interests with their needs. Or contribute at any of these single-day events: Stream Monitoring (teens and adults), have fun collecting stream invertebrates, May 1; Fish Survey (for teens and adults), May 29 & June 26. Great Herp Search (for ages 6 and up), search for amphibians and reptiles, June 5 & June 12.