By Claire Whitcomb for NJ.com

“Over the river and through the woods” is as synonymous with Thanksgiving as turkey and pumpkin pie. But where exactly are the woods these days? And how much of our rivers are hidden as we zoom over cement bridges, thinking only about the traffic between here and the cranberry sauce?.

New Jersey is the most densely populated state in the nation, with more urban terrain than forests, according to a 2015 study by Rowan and Rutgers universities.

What’s worse is that most of us can’t tell the forests from the trees. Me included.

This fact is especially embarrassing, given that I am chair of the environmental commission in Madison and live spitting distance from a rare, intact 53-acre forest on the Drew University campus.

I am sorry to admit that it took me 23 years and the threat of a land sale to realize that the Drew Forest was ecologically different from my yard — and the rest of the trees on Drew’s notably leafy campus.

This is not to say that I didn’t know it was important. I could spot the Drew Forest on an aquifer recharge map (it was the bright blue area that was super important). I knew its extensive canopy mitigated the heat island effect (ie., it kept Madison cool). But I didn’t know what so many Drew science students have learned in the course of their outdoor studies and research: A forest isn’t just a bunch of trees that you can swap out like last year’s wardrobe. It’s an ecosystem.

It crumbles when you slice and dice it, its environmental benefits can’t begin to be replicated by planting juvenile trees here and there in parks or on suburban lawns. Scientists learn more every year about what goes on beneath the forest floor and it is clear that trees talk to each other and share nutrients through vast fungal networks.

Fortunately, environmentalists have their own networks. This spring, we came together to create Friends of the Drew Forest. To us, along with the town council and 10,000 signers of our petition, exploring a conservation sale seemed — and still seems — like a climate-smart way to preserve open space and raise funds for an esteemed university that is facing financial challenges common to many small liberal arts institutions.

And so I set off for a forest walk on a hot buggy day, accompanied by a videographer and Dr. Sara Webb, forest ecologist and Drew professor emeritus. For the last 12 years, Dr. Webb has overseen the restoration of 22 acres of Drew’s “living laboratory.” That sounds easy, but as we walked she described a herculean effort that required an army of volunteers, a decade of student interns, several far-sighted donors and the support of the U.S. Fish and Wildlife Service.

The result: The 22 acres we were filming have been protected by a deer fence since 2011 (donated by Dr. Christine Hepburn). The “empty forest syndrome,” common to New Jersey forests, has been dramatically reversed. “To see this kind of lush understory of native plants and native trees,” Dr. Webb told us, “you’d have to go to protected preserves in the Catskills.”

Success wasn’t the least bit guaranteed.

The restoration team pulled invasive species, wrestled the trees from the grip of Asian wisteria and bittersweet vines and tried to level the playing field by planting hundreds of saplings and wildflowers. The ecosystem sprang back. Given a chance to compete, native trees — tulip poplars, black gum and sassafras — took root. Wildflowers made surprise appearances, butterflies and moths reappeared.

Raptors began perching on the tallest trees, screech owls swooped and herons and egrets began frequenting the forest’s two glacial ponds.

Today the forest is vital and alive — even the dead parts.

Fallen trees show off architectural ladders of fungi; dead branches litter the ponds, providing roosts for turtles to sun themselves, perches for white egrets and green herons and protected habitat for amphibians and fish to lay their eggs.

All of this happens beneath a canopy of some of the oldest trees in Morris County. How old? Surely many were there when, in 1867, Daniel Drew purchased an estate called The Forest in order to found a Methodist seminary.

These magnificent oaks, maples, beeches and tulip poplars — the grandfathers and grandmothers of the forest — deserve respect and gratitude. They store the most carbon and support the most varieties of wildlife, from the pollinators and mosses to the spiders and owls.

A forest needs elders. Just like a Thanksgiving table.

This is why, on the fourth Thursday of November, as proclaimed by Abraham Lincoln in 1863, we pause to give thanks. And those of us who are close enough in terms of geography and temperament go over the river and through the woods with a common emotional destination: grandmother’s house.

Claire Whitcomb is a writer and chair of the Madison Environmental Commission.