Wildlands & Woodlands Website

Highstead works to inspire curiosity and build knowledge about plants and wooded landscapes in order to enhance life, preserve nature, and advance sound stewardship practices.

2013 Spring Open House and Trails Day

Climate Change Causing Early Flowering of Plants





Richard Primack

Common plant species are flowering 10 to 14 days earlier in Concord, Mass., compared to over a century ago because of rising temperatures, according to botanist Richard Primack in a talk on June 1 at Highstead.

Highstead is a nonprofit organization dedicated to ecological research and regional land conservation through its leadership in the Wildlands and Woodlands Initiative, a collaborative effort of individuals and organizations across New England committed to protecting our forested landscapes and the ecological, economic and cultural benefits they provide.

Primack, a professor of biology at Boston University, said the average flowering time of 30 common wildflowers is May 4, which is 10 days earlier than when Henry David Thoreau, a philosopher and nature writer, observed them in the 1850s.

“In a very iconic place like Concord, plants are responding to climate change at least in terms of their phenology,” he said.

He and Peter del Tredici, a senior research scientist with Harvard University’s Arnold Arboretum, confirmed the early flowering times by comparing herbarium specimens with plants on the arboretum’s grounds, and that rising temperatures were driving the changes.

Become a Citizen Scientist

The field of phenology is undergoing a renaissance. Many national initiatives exist for monitoring phenology, so opportunities abound if you want to become a citizen scientist.

Project Bud Burst - A network of people across the United States monitoring plants as the seasons change and submitting ecological data based on the timing of leafing, flowering and fruiting of plants. budburst.org

Journey North: A Global Study of Wildlife Migration and Seasonal Change - Participants share field observations across the northern hemisphere, exploring the interrelated aspects of seasonal change. www.learner.org/jnorth

USA National Phenology Network - Monitors the influence of climate on the phenology of plants, animals and landscapes. usanpn.org

eBird – Provides rich data sources for basic information on bird abundance and distribution at a variety of spatial and temporal scales. www.ebird.org/content/egird/

Hummingbirds Home - Learn more about hummingbirds and how to protect them. www.hummingbirdsathome.org/

Thoreau systematically observed over 300 species of plants, keeping meticulous records and detailed journals that have formed the basis of Primack’s research. Primack and his colleagues made observations of the same plants that Thoreau saw in the exact same places. They discovered that 14 of 21 species of orchids found in Thoreau’s time had disappeared from Concord, and Primack thinks most of that loss has occurred in the last 50 years.

"Climate change is a factor,” he said. “Cold-loving northern species disproportionately have a tendency to decline compared to more warm-loving southern species.”

Average temperatures in March and April in the metropolitan Boston area, he said, have risen 5 degrees Fahrenheit since the 1850s—the same rate that the rest of the country is expected to experience over the next 100 years as global warming accelerates. Primack attributed two-thirds of the most recent warming to urbanization and the rest to climate change.

He said today’s climate in Massachusetts is similar to Connecticut’s climate 40 years ago. In a couple of decades, he predicts, the climate in Massachusetts will be like New Jersey’s today, and by end of this century possibly like North Carolina’s. “Pretty sobering,” he said.

Primack said that while milder winters and early springs might seem appealing, warming temperatures foreshadow serious problems. Vernal pools and swamps, where endangered amphibians and wildflowers live, will dry out. A lot of species will go extinct, and forests will become susceptible to invasive species and insect and fungal attacks.

“There’ll be a lot more ticks, more Lyme Disease and more mosquitoes creating insect-borne diseases. There’ll be frequent flooding in New York, Boston and other coastal areas.”

Ecologist Ed Faison, right, leads a public tour
of the Highstead property before a lecture by
botanist Richard Primack, second from left.

In addition, earlier flowering times will affect local economies and the way people perceive cultural traditions as plants respond to warmer conditions. Last year, he said, a late frost damaged the Massachusetts apple crop, and Patriots’ Day, a civic holiday in mid-April commemorating the start of the American Revolution, took place under budding trees.

“People may think Patriots’ Day is a springtime holiday, but the Revolution’s beginning actually occurred at the end of winter in terms of the still-dormant trees.”

In addition to writing Walden, Thoreau made detailed observations about the arrival time of birds and trees leafing out in the spring. Primack found that half of all bird species in Massachusetts are showing little evidence of responding to climate change.

“Birds are arriving just a couple of days earlier than in the past. They respond a little bit to temperature and a little to wind direction and storm systems, but to a much lesser degree than plants.”

The danger to birds, Primack said, is they might arrive too late in spring to capture the big pulse of insects, which feed on early-flowering plants.

“As a result of climate change, bird populations will decline because their timing might be mismatched with that of plants and insects.”

It turns out that Thoreau was writing about the same topic 150 years ago: “Insects and the smaller animals follow vegetation. … The greater or less abundance of food determines migrations. If the buds are deceived and suffer from frost, then are the birds.”