I’ve taught as an adjunct instructor in the biology department at Merrimack College for over 20 years. But I’m not teaching this year. Because of the pandemic, the college has temporarily cut back on the use of adjuncts.
I usually teach an ecology lab in the fall. Most sessions are outdoors, providing the opportunity to explore various habitats and to teach students about the biology of some of the plants and animals we see.
For the first lab, we usually go for a nature walk in the Dale Street Conservation Area along the Shawsheen River in Andover. I prompt students to ask questions about what they observe and to think about hypothetical research projects based on their observations — to get them to start looking at the world like scientists do.
Since I’m not teaching this semester, I decided to take a walk along the river by myself. It’s bright and sunny, with temperatures in the low 80s — about as nice a day as you’re likely to experience in Massachusetts.
Before I head into the woods, I walk around the edge of the dirt parking lot to look at some of the plants. Last year, I talked to the students about the numerous exotic invasive species that grow here, like Ailanthus, buckthorn, and Asian bittersweet. I told them how most of these invasive species were originally brought to the US from Europe and Asia as ornamentals to decorate city streets and peoples’ yards. But some of the plants spread into the surrounding landscape where they now compete with native species.
I picked some leaves from an Ailanthus tree, crumpled them in my hand, then asked the students what they smelled like. “Peanuts,’’ one of the students replied. “That’s right,’’ I said. “Now you know one way to identify Ailanthus.’’
I then pulled a wild carrot, also known as Queen Anne’s lace, from the ground, and snapped the root open. As its name suggests, the root smells like carrots. The students had a harder time with this one, so I told them another way to identify wild carrot is by its clusters of tiny white flowers.
I always enjoy teaching students how to identify different species of trees and other plants. As they jotted down notes and took photos with their cellphones, I could see a sense of satisfaction on their faces. They had doubtless seen some of these plants before, and probably didn’t think much about them. Now they were learning the plants’ names, how to identify them, and something about their biology.
I start down the trail that follows the river through the woods. The Shawsheen is a small river, about 20 or 30 feet wide in this area, and a couple feet deep. The water level is low and the current flows slowly, as we’re in the midst of a late summer drought. The river is heavily shaded by large trees. Maples, oaks, and white pines tower 60 to 70 feet above me.
There’s lots of poison ivy growing along the edge of the trail. The students are often afraid of it. Having had my fair share of poison ivy rashes, I guess I can’t blame them. Last year I told the students it has clusters of three shiny leaves, and I pointed out poison ivy plants whenever I saw them.
One student saw a vine with clusters of five leaves and asked if it was poison ivy. “No,’’ I replied. “It’s Virginia creeper.’’ She paused for a moment, then she asked me if I was sure. I smiled and said, “Yes, I’m sure.’’
I walk across a wooden foot bridge that goes over a shallow, muddy pond connected to the river by a small stream. I’m startled by a muskrat that dives into the water beneath me and rapidly swims away. I don’t recall seeing muskrats on our previous nature walks.
The forest gives way to a bright open area, and I step onto a boardwalk that traverses a broad swamp. A thick tangle of wild grapevines is growing on both sides of the beginning of the boardwalk.
I’m surprised, and a bit disappointed, that there’s no grapes on the vines. Last year, there were lots of grapes and I picked a few to show the students. One of them asked if they were edible. Yes, I told her. And they’re a popular food item for some of the birds and mammals that live in these woods. I talked briefly to the class about seed dispersal — how plants invest energy into the production of tasty, showy fruits that attract animals that eat the fruits and spread the seeds in their droppings. A good deal for both the plants and the animals.
I continue walking slowly across the boardwalk, stopping occasionally to take photos. Colorful dragonflies flit among the cattails and purple loosestrife. A pair of goldfinches flies across the swamp and lands in the shrubs on the other side. A flicker calls from the forest.
I’m surprised to hear the trill of a gray treefrog. I’m used to hearing them at vernal pools during the spring breeding season, and occasionally after a midsummer thunderstorm, but I don’t ever remember hearing them this time of year.
I wish my students were here to listen to the treefrog with me.
Don Lyman is a biologist, freelance science journalist, and hospital pharmacist who lives north of Boston. Send your questions about nature and wildlife in the suburbs to donlymannature@gmail.com.
This article appeared in the Boston Globe 10/11/20. The author and SRWA may have seen each other while hiking.
Footnote: This is the same area as the previously posted hike.