When Rod Serres thinks about cranberries, he doesn't see them beside a Thanksgiving turkey. Another bird comes to mind: a canary in a coal mine. That's because, like all berries, cranberries are very sensitive to climate, making them the agricultural harbinger of global warming in America's Northeast.
"The cranberry is pretty highly adapted to its specific environment, its niche in life," says Mr. Serres, principal scientist for Ocean Spray, an agricultural cooperative and juice company headquartered in Lakeville-Middleboro, Mass. "And if you change its environment, it's probably going to be affected more than most species"
Cranberries were a late-season staple for native Americans in New England for thousands of years and have played key roles in American history, historians say. Early European settlers in Plymouth survived cold winters with help from cranberries, which native tribes taught them to harvest from the region's bogs.
Now the red berry, ubiquitous during the holiday season, is expected to retreat north later this century, deserting some key growing regions.
A recent report by the Northeast Climate Impacts Assessment (NECIA), which looked at the impact of global warming on the Northeast's character and economy, says the region's food commodities are likely to be hit hard, with berries perhaps feeling it most of all. The report, a two-year collaboration between the Union of Concerned Scientists (UCS) and a team of more than 50 independent scientists and economists, points to two greenhouse-gas-emission scenarios (one high, one low) mapped out by the Intergovernmental Panel on Climate Change. The NECIA used the data to forecast a range of climate effects in nine states, from New Jersey to Maine.
A host of environmental pressures are exacerbated by global warming, scientists say, ranging from more weeds and pests to reduced winter chill periods. That could threaten the viability of berry production generally, while all but wiping out cranberry and Concord grape production in the region's southernmost states. The report warns that as temperatures rise and growing seasons lengthen, the minimum chilling requirement needed for fruiting buds to mature may not be met, causing a precipitous drop in fruit yield as far north as Massachusetts.
Peter Beaton, a third-generation cranberry grower here in Wareham, Mass., near the Cape Cod Canal, has seen growing effects from what he concludes is a warming climate since the 1970s.
"Quite often, when you would get into late October or the first of November, there would be an inch or two of ice on the bogs when it was time to harvest the cranberries. And that was not a rare occurrence – that was a common occurrence," says Mr. Beaton, outgoing president of the Cape Cod Cranberry Growers Association (CCCGA). He can't recall a time once during the past 10 years when the cranberry harvest was delayed because of ice. The CCCGA, founded in 1888, represents 87 percent of the cranberry growers in Massachusetts.
Cranberry growers can flood bogs to shield their crop from winter frosts and summer heat, thereby protecting the cranberries from temperature extremes. Other berry growers cannot resort to such tactics, as most berries cannot survive submerged for very long.
A sharp frost in late April 2007 ravaged grape and blueberry blossoms that had emerged during an unusually warm period, killing up to 90 percent of the blossoms from Missouri to Alabama and the Carolinas. This type of stop-and-go winter is exactly what people in New England's lucrative berry industry are concerned will become more frequent.
Some researchers are less concerned about temperatures being cold enough to mature fruit than they are with erratic weather patterns brought on by climate change. More frequent droughts and floods, as well as salt-water incursion from hurricanes and rising sea levels pose serious risks.
"The more frequent occurrence of extreme weather is probably what is going to hit us first," says Serres. "If [droughts and hurricanes] happen more than once every five years, it's really going to impact the industry."
Drought, coupled with unseasonably warm weather, has reduced the average size of a cranberry by roughly one-third this year. The United States Department of Agriculture had forecast a Massachusetts yield of 180 million pounds, a yield now expected to fall short by some 31 million pounds, according to the CCCGA. At about $45 per 100-pound barrel, that translates into roughly a $14 million shortfall. Massachusetts produces one-third of the world's cranberries, surpassed only by Wisconsin.
"There has always been some fluctuation to some degree," says Jeff LaFleur, executive director of CCCGA, but not to this extent, with 30-million to 40-million-pound swings in production lately. "These swings seem to be really too aggressive," he says, pointing to unprecedented variations in temperature and rainfall.
The weather is beyond growers' control, but scientists at the University of Massachusetts' Cranberry Station in East Wareham are looking more closely at how to combat the pathogens they expect to increase with warmer temperatures.
One method of interest is subsurface irrigation (drip irrigation), a technique already used at many bogs in New Jersey. That state's high humidity encourages the growth of fungi and pathogens in marshes. By flooding the bogs from the bottom up, rather than with overhead sprinklers, the leaves and fruit stay drier, inhibiting rot and other maladies.
And while installing drip irrigation systems can be costly for small farmers, it is increasingly seen as a wise investment. Besides reducing water costs and pesticide use, this method also conserves water – and climate change could mean stricter water management.
Hardier hybrids could also help. While cranberry hybrid development has thus far been focused on improving fruit yield, nutrition, and color, Carolyn DeMoranville, director of the UMass Cranberry Station, says more attention will need to be put on developing disease- and drought-resistant types.
Ms. DeMoranville warns that these solutions may not help with global warming's long-term effects: "If we're talking about numerous degrees of difference in 50 years, that may be beyond working with the tools we have. But presuming that somebody decides to finally start doing something about climate change, then I think we would still have the tools ... to deal with the amount of change that's predicted in the less-drastic models."
Meanwhile, some growers worry that their once-ideal growing zones are relocating north. "I believe that the industry more than likely is heading north even without a climate change because we do need to fill the demand," says Beaton. Climate change "will just accelerate the move north for the industry."
Now, with fewer killing spring frosts, Quebec has surpassed Maine as the world's largest producer of wild blueberries, according to the University of Maine at Orono. With an annual average production of about 110 million pounds since 2001, growers of wild blueberries in Eastern Canada have outproduced Maine growers by some 45 million pounds a year since then.
While New England growers of European varieties of wine grapes will continue to experience a boost from rising temperatures, native varieties are likely to suffer. "The Concord grape is particularly vulnerable and requires longer winter chill and cooler temperatures than many of the European grapes," says Peter Frumhoff, director of science and policy at the Union of Concerned Scientists and chair of the NECIA team. "Producers may ultimately adapt by changing to warmer-temperature varieties where that's possible."