Kevin Riordan: The upper Cooper River trail, a treasure that many miss

To walk the upper Cooper River trail is to discover a secret hidden in plain sight.

Who knew so much woodsy, watery, almost-wilderness awaited visitors to this corner of South Jersey, where Cherry Hill and Haddonfield meet?

"I've lived here all my life," says Bob Feltoon, an attorney from Voorhees. "I take Park Drive all the time. And I've never walked back here."

Says Merchantville businesswoman Marilyn Axler, an active gardener and park patron, "I didn't know about this."

Longtime Camden County Park system fans like Feltoon, Axler, and me are delighted to discover the twists and turns, the footbridges and scenic ridges, of a landscape we've driven by for decades.

Our 1.5-mile Sunday morning walk is a pleasure despite the pre-spring beigeness of the vegetation and the coolness of the air; the serpentine stretch of streams, pools, and ponds that comprise the Cooper looks chilly, too.

"Thanks for coming to our first 'Talk and Walk,' " Michael Hogan says as about a dozen explorers - most of us middle-aged or older - gather inside the county's Environmental Center.

The green-roofed facility adjacent to the parks department's longtime headquarters on North Park Drive in Cherry Hill opened in 2011. Built for $2.4 million, about half of it from a state green-energy grant, the center has begun to host organizations, programs, and events on a regular basis.

The free "Talks and Walks" will focus on the Cooper watershed's flora, fauna, and history, and will continue biweekly through June 16.

"The freeholders really want the center to be a hub of environmental activity for the region," Jack Sworaski, the county's director of environmental affairs, tells me.

And Freeholder Jeff Nash notes that the center complements the Sustainable Camden County initiative, as well as the redesign of walkways, landscaping, and lighting under way in an adjacent portion of Cooper River Park.

The county hired Hogan's employer, the nonprofit South Jersey Land and Water Trust, to organize volunteers and host the walks.

The trust recently received a $7,600 Subaru of America grant to fabricate and install seven handsome "watchable wildlife" informational signs for the park, which is home to small mammals (including muskrats), the occasional marsupial (possums), as well as an aviary's worth of sparrows, cardinals, robins, nuthatches, chickadees, and woodpeckers.

"The upper Cooper is an interesting mix," says Hogan, who grew up in Bellmawr and now lives in Atlantic County.

We're standing near the edge of picturesque Hopkins Pond, where a gaggle of geese squawks with alarm as two red-tailed hawks circle confidently above.

Hogan points out the imported English ivy that has emigrated from private gardens and seems to be flourishing in the park. But so is the venerable (if not exactly beloved) indigenous wetlands dweller most people call skunk cabbage.

"It's nice to see them surviving," says Hogan, an experienced nature photographer.

"Three hundred years ago there were probably swamp pinks here and all kinds of [other native] orchids," he adds. "But all of that is gone because of deforestation and erosion, starting in colonial times."

Also gone, Hogan adds, are the once-abundant chestnut and white cedar trees; the first to blight, the second to logging.

But other vintage elements of the landscape endure, including the marl, or clay, deposits that lend a pale gray-blue tinge to Hopkins' rippling water - and preserved the skeletal remains of Haddonfield's famous dinosaur, found nearby a century and a half ago.

"Look," Hogan says, gesturing toward a stand of trees near the water's edge. "There goes another downy woodpecker."

Cool.