Tracking Global Warming Through Botany

By JACK SHEA

Our plants are warning us that global warning is real, according to Boston University phenologist Richard B. Primack. Phenology studies how biological phenomena, such as plant life, are affected by climate and seasonality.

Research shows that plants are already adjusting to a six-tenths of one percent global temperature rise and they are reacting even more dramatically in what are termed heat island-effect cities such as Boston, Mr. Primack noted. Boston’s average temperature has risen five degrees Fahrenheit over the past 120 years compared with a two-degree rise for eastern North America as a region, Mr. Primack wrote recently.

What the math in that trend means for the Vineyard is, for example, that our roses would bloom in February in 2107 rather than in May this year. Mr. Primack’s painstakingly detailed analysis of same species and in some cases the same plants over time indicates to him that plants flower four days earlier for roughly each half degree increase in Fahrenheit temperature. In a telephone interview yesterday, Mr. Primack said warming effects on the Vineyard may be lessened by a cooler ocean environment, but he noted that shifts in the Gulf stream could change the warming pattern. The Vineyard may be one degree cooler than one hundred years ago, he estimated. He noted that studies of fish migratory patterns show that in warming ocean areas such as Southern California, the stocks of cold-loving fish are declining and those of warm-loving fish are increasing.

Plants around the world are leafing and flowering days, weeks, even a month or more earlier than they did 25 years ago, same-plant studies have shown. Drawing on his research at the Arnold Arboretum in Boston and on other long-term studies, meteorologists expect worldwide temperatures to rise five to ten degrees over the next 120 years, Mr. Primack wrote recently, adding: “This change is comparable to the one that occurred after the last Ice Age.”

Mr. Primack will discuss his work and its implications on Wednesday evening at 7:30 p.m. in the far barn at the Polly Hill Arboretum. His lecture, Global Warming in Our Own Backyards is the David H. Smith Memorial lecture sponsored by the Polly Hill Arboretum.

Mr. Primack will also be a panel speaker at Rising Tides: A Global Warming Forum at 7:30 p.m. on Saturday Aug. 4 at the Grange Hall in West Tisbury, co-sponsored by the Polly Hill Arboretum and the Martha’s Vineyard Museum.

The warming trend could change the world, Mr. Primack said in an article in Arnoldia, a publication of the Arnold Arboretum. Near-term effects include a week or two longer growing season and a shift in concern about plants from winter hardiness to drought survival. Plants may also migrate or become extinct as a result of change,

In Massachusetts, scientists have observed earlier flowering, bird migrations and frog reproduction cycles, Mr. Primack wrote. He used an example from the Netherlands in which a flycatcher bird species population was diminishing. Tracking back, researchers found trees were flowering earlier, so caterpillars bred earlier and were not available to feed the flycatcher fledglings who arrived later at their normal historical cycle.

Quietly, literally for centuries in several cases, enthusiasts have been paying attention to details of plant life as the rest of us briefly noticed the flowers.

Mr. Primack believes that those historical plant records may be a boon to understanding the global situation.

“Clearly observations of phenological events in plants will play an important role in our efforts to evaluate the effects of rising temperatures,” he wrote in Arnoldia. “Climate change will affect the full range of organisms — plants, fungi, animals and even microorganisms — but the sudden onset and cessation of flowering in plants make them particularly well-suited to research on its effects.” He also wrote: “More important[ly], we have extensive records of plant flowering times going back decades and even centuries.” Indeed, the Marsham family of Norfolk County in the United Kingdom began detailed recording of plant and bird life in 1736 and continued the practice until 1947.

Mr. Primack and his student team shifted their focus in 2002 from purely scientific to an ecological perspective. “We found, editing our botany college textbooks, that environmental impact was increasing. But the examples were from distant places, not local.

We believed we could find examples in Massachusetts of global warming that residents could see,” he said, adding:

“A great example is that we have detailed plant and bird records from Thoreau in his handwriting recording activity in Concord between 1852 and 1858.

We replicated exactly the work he did. The plants flower eight days earlier today than in the 1850s.”

New England, particularly Massachusetts, is a gold mine for research, Mr. Primack said.

“We have old universities, old natural institutions, such as the Botanical Society and the Arnold Arboretum, with good, intact records that are readily available.”

Mr. Primack is willing to publicize his findings.

“We have always written for the scientific journals but now we write popular versions to promote better understanding for nonscientists”, he said, noting that his team works with writers from publications like The Smithsonian and makes presentations.

“That’s how we came to be on the Vineyard this week,” he said.

Close to home, Mr. Primack works with Trevor Lloyd-Evans, senior research scientist at the Manomet Bird Observatory on Cape Cod to study bird migration patterns.

“Trevor has a lot more information [than I do] but we’re finding that migratory birds that winter in the continental U.S. are arriving earlier than they were and birds from Caribbean and tropical climates are arriving on their historical dates,” he said.

Mr. Primack could not tell us whether the cliff swallows will arrive on schedule to eat our pesky Vineyard green flies.

But noting strong conservancy efforts on the Vineyard, he said:

“We have to manage and protect the habitats as well as deal with greenhouse effects.”