Today's focus tree is the sugar maple, and Suzanne Mrozak is ready. In her bag is a jumble of maple candies and cookies. In her ears dangles a pair of red maple leaf earrings — obviously.

Standing in front of Mrozak is a handful of volunteers jotting down notes. Leaf color? They look up at the enormous canopy of the tree. Yes. Fruit drop? They look down at the brown seeds littering the ground. Yes.

They're members of a group called the Tree Spotters, a program that trains volunteers to be citizen scientists at the Arnold Arboretum. The Tree Spotters monitor the life cycles of trees, noting when they bud, grow leaves and turn colors. The data they collect is then used by scientists at the arboretum and all over the country to study everything from seasonal allergies to how climate change may be affecting New England's trees.

They know how to have fun, too. Mrozak, a former Genzyme employee who is now the program’s volunteer coordinator, bubbles with energy as she pulls cider out of her bag. “I like making things happen,” she said, and if you glance at the peppy newsletter she puts together — called, naturally, “Spot On!” — you get an idea of what she’s talking about. There are calls for book clubs and links to botany-themed coloring books. Every year they have a holiday potluck and a July cookout.

Suzanne Mrozak, the volunteer coordinator for the Tree Spotters program, observes a leaf of a sugar maple tree at the Arnold Arboretum.
Amanda McGowan/WGBH News

Next to Mrozak is Catherine Chamberlain, a scientist at the arboretum who studies late freezing events, or cold snaps in the spring that can wipe out the buds of plants. While her dog, Kylie, waits patiently at her side, she explains to the volunteers that sugar maples — the fiery red icons of New England autumns — are finicky trees, sensitive to competition from other plants, shade and the stresses of urban environments.

Scientists like her are worried about the impact that warmer winters and shifting springs may have on them and other trees.

"There's all sorts of things that could happen," Chamberlain said, ticking off a few examples.

It’s possible that trees may be able to adapt to shifting seasons (spring, for instance, camethree weeks early in some areas of the U.S. this year) but their pollinators may not. Trees could start dropping seeds earlier in the fall or even late in the summer, before squirrels are ready to collect them. That could spell trouble later in the season.

Another scenario: as warm temperatures come earlier in the spring, trees may start to bud earlier — only for those buds to freeze when the last frost arrives.

“We might see more of these intense spring freezing events that could really hurt the trees,” Chamberlain said.

This is where she turns to the Tree Spotter data.

"The information our Tree Spotters collect is very useful," Chamberlain explained. "I can already look back the last couple years and see how each year has changed, and how these different temperatures in the spring have affected that time frame."

Kylie attends Tree Spotting sessions with Catherine Chamberlain, an environmental scientist at the Arnold Arboretum.
Amanda McGowan/WGBH News

The Tree Spotters record data with an online platform called “Nature’s Notebook”which is run by the National Phenology Network (phenology is the scientific term for how seasonal changes affect living things). The platform, which anyone can use and add observations to, can be used to track trees or other plants as well as animals. Scientists can then access the database for their projects — recent examples include a study on how climate change is impacting bird migration and one on how warming temperatures may lead to the growth of more ragweed, which could increase seasonal allergies and asthma in humans.  

Volunteer Doris Corbo pulls up the Nature’s Notebook app on her phone and demonstrates how easy it is to record observations. (Volunteers can also print datasheets from the website and enter the data online later.) Corbo lives nearby and her children learned to walk and ride their bikes here, so the arboretum is a special place for her. But she was also interested in getting involved in climate change action close to home.

“That was what was attractive to me — just, as an average citizen, being able to make a contribution towards something larger than yourself,” she said.

Chamberlain says that’s what has been drawing a lot of people to citizen science programs these days.

“You hear about all these things that are happening in the world. Lots of shifts are happening to our habitats,” she said. “That’s why people are coming in — to learn about how climate change is impacting them."

Volunteer Evie Weinstein-Park learned about the Tree Spotters on a walk through the Arboretum with friends. She’s a fourth grade teacher and hopes to introduce Tree Spotting to her students.

“The kids are always in a rush, and we rush them a lot,” she said. “I feel like looking at something really long and hard, the more you look the more you see. It’s a good activity for kids nowadays, maybe any day, but especially now when everybody goes so fast.”

“I think sometimes we lose touch with the outside world,” Weinstein-Park continued. “It just feels so good to be outside on a day like this, to really be looking and noticing. It’s miraculous.”