Half of the plants described by Henry David Thoreau in his classic 1854 book “Walden” have disappeared from Walden Pond.

That is an example of how relatively rapidly climate change can modify our natural environment, said University of Maine Cooperative Extension and Maine Sea Grant climate change educator Esperanza Stancioff in a news release.

A new statewide “Signs of the Seasons” bio-monitoring program recently launched by Stancioff, Beth Bisson, the assistant director of outreach and education and co-coordinator of the program, and colleagues will use volunteers to monitor Maine’s phenology, or nature’s clock.

The project is partially funded by an $8,000 grant from UMaine Extension and recently a $10,000 grant from the U.S. Fish and Wildlife Service, along with in-kind contributions from other collaborators. The goal is to recruit and train members of the public to assist scientists in observing and recording local effects of climate change on Maine’s plants and animals in hundreds of backyards in dozens of communities.

Extension (extension.umaine.edu) and Sea Grant (seagrant.umaine.edu), in conjunction with the USA National Phenology Network (usanpn.org) and educators and scientists from more than a half dozen organizations and institutions, have been training citizen scientists from all walks of life in every age group to help with “Signs of the Seasons: A Maine Phenology Project.” (umaine.edu/signs-of-the-season).

“We have an incredibly diverse audience for this throughout the state,” Stancioff said in a news release. “There has been more interest and enthusiasm than we had expected.”

More than 170 volunteers already have been trained this first season to monitor the Signs of the Seasons “indicator species,” by observing and recording life cycle events like the appearance of first buds, leaves and flowers, the arrival of monarch butterflies, and the developmental phases of rockweed.

A change in the timing of one species can have ripple effects on others. For example, “What happens when milkweed, which is food for monarch caterpillars, is not ready when the eggs hatch?” Stancioff asks.

Just as many people closely watch the timing of ice-out on Maine lakes, Stancioff is finding that people are interested in making observations where they live, and providing much-needed data to scientists studying environmental changes.

Stancioff and Bisson are working with co-principal investigator Mitch Mason, a Cooperative Extension 4-H Youth Development Educator in the Cumberland County office, and entities including Acadia National Park, Schoodic Education and Research Center, U.S. Fish and Wildlife Service, Maine Maritime Academy, Maine Audubon, and climate scientists and educators at the University of Maine. Participants include Extension’s Master Gardeners and 4-H Youth Development groups affiliated with Cooperative Extension, and other groups already working in Maine’s coastal environment.

“What I’ve been hearing as a climate change educator locally and nationally is people need to be able to understand how our climate is changing in an engaging way that’s meaningful to them,” Stancioff said.

The complete list of 13 indicator species are the red maple (Acer rubrum), sugar maple (Acer saccharum), common dandelion (Taraxacum officinale), common lilac (Syringa vulgaris), forsythia (Forsythia), wild strawberry (Fragaria virginiana), milkweed (Asclepias syriaca), Monarch butterfly (Danaus plexippus), American robin (Turdus migratorius), common loon (Gavia immer), ruby-throated hummingbird (Archilochus colubris), rockweed (Ascophyllum nodosum) and the beach rose (Rosa rugosa).

Anyone interested in learning more about Signs of the Seasons volunteer opportunities is encouraged to contact Stancioff’s office at 832-0343 or call toll free in Maine at 1-800-244-2104. Community monitoring groups, individuals, families or school teachers and students are invited.