In October, cranberries fell from a conveyor belt into a long-awaited truck in Edgewood Swamp, Carver, Massachusetts. Workers walk into the cold swamps to pick these bright red berries, and in recent decades cranberries have been an indispensable food on the Thanksgiving table.
摄影：JOHN TLUMACKI, THE BOSTON GLOBE, GETTY IMAGES
Written by: Alejandra Borunda
Five years ago, the Davenport family bought a nearly 50,000-square-meter cranberry swamp in the small town of Cape Cod, and they knew it would be no easy task, but they were ready: digging out the poisonous ivy wrapped around the cranberries; not letting the spiders form webs on rakes and brackets, tools used to pick crimson fruit from the flood swamp; and sleeping in trucks next to the swamp on cold nights, ready to activate sprinklers to protect the cranberries from freezing.
But every fall, the joy of harvest makes all the effort meaningful, says Tabatha Eldridge, the wife of the swamp owner. With yellow-brown leaves floating on the swamp and tannic water oozing with chill, her husband and son walked across the soft ground and gently delivered the fruit floating in the water to the waiting truck: it was the fruit of their labor.
Millions of years of evolution, thousands of years of consumption, 200 years of careful cultivation, coupled with years of hard care, this is the cranberry they love. But the future prospects for these vine plants are unknown. In New England, as elsewhere, climate change is changing the environment in which these plants grow, from warm winters to ever-changing summers. These changes have made them harder to grow, casting a shadow over the much-loved Thanksgiving signature food.
Growers who love crops and scientists who help them are struggling to find solutions, and the situation is not so bad. But for growers like Eldridge, so far, "we don't have an alternative," Eldridge said.
Adapt to the harsh weather of New England
The need for cranberries is very special.
Blueberries, a close relative of cranberries, concord grapes and cranberries, are three common fruits native to North America. The Algonquin people call cranberries "sassamenesh", the Wampanoag and Lenny Lainape people call them "ibimi", and the indigenous peoples of the East Coast use this more sour "sourberry" as a dye and medicine. Some tribes crush and dry cranberries along with meat or fish for easy preservation and portability.
A worker surrounds the cranberries floating on the surface of the water and sucks them out of the swamp with a suction hose next to them. This year's sweltering heat and drought have caused some growers a lot of difficulties.
Later, after contact with Europeans, sailors who left the East Coast discovered that if they regularly ate "cranberries" rich in vitamin C, they would not get scurvy. Today, Massachusetts is the second-largest producer of cranberries in the United States after Wisconsin, producing more than 100,000 tons a year; it's the state's most important agricultural product, with an annual output value of about $100 million.
The cranberries in both states come from advancing glaciers, which leave holes in the hard bedrock. As the glaciers receded, these voids became swamps: moist, lush vegetation, and often sandy acidic lowlands.
At the edge of the swamp, cranberries thrive. They adapt to large amounts of water, harsh winters and mild summers.
Without an official map of the Cranberry Swamp in Massachusetts, Descartes Labs devised a machine learning algorithm that used data from sentinel 1 satellite 2018 to locate and map the swamp. This image shows their statistical results, and the red area is most likely cranberry swamp.
Cranberries spread their seeds by water, not by wind or wildlife: when the fruit ripens, it falls from the vine and floats away, and the small air sacs around the core allow them to float on the water and come to the edge of the new swamp, where the seeds take root and sprout.
Winters in the north are freezing cold, and cranberries go into a protective dormant state. Still, scientists don't know the exact answer to how they calculated this cold time. Depending on the length of time, cranberries decide when to fall asleep in the fall and when to wake up in the spring: they need at least 70 days of cold to germinate normally, and the temperature is between 0 and 7 degrees.
Libby Ellwood, a biologist who studies the impact of climate change on plants, said: "Plants rely on the cold winters and dormant cycles of each year to learn about the arrival of spring. ”
Cranberries are also picky about heat, and summer temperatures are too high and leaves and fruits can be roasted. By the middle of last summer, the next season's buds had already emerged, and this year, the ripe fruit was still on the vine. This means that both are susceptible to hot weather, so a strong summer heat wave can severely damage multiple cranberries harvests. If the temperature is too high and too dry, the cranberries will be "burned", and sometimes even the peel is ripe.
Global change
Brian Wick, executive director of the Cape Cod Cranberry Growers Association, said record-breaking situations are now seen almost every year. "The temperatures are highest here and the driest there. Extreme weather is no longer an anomaly, but an anticipated situation. ”
Throughout the year, swamps like Eldridge's cranberry swamps are beginning to feel the effects of climate change.
The situation is evident in the summer. This year was the hottest year in Massachusetts on record. When the temperature exceeds 32 degrees, growers often use cold water to cool the cranberries, which is expensive and laborious. This summer, high temperatures combined with severe droughts have left growers such as Eldridge panicked.
The harvest time was also delayed as a result. Since the first cultivation of cranberries in the early 19th century, it has been harvested in September or October. Now, Wick says, "the seasons have changed, it's not necessarily going to come sooner than we thought. There are no cool weather in late summer and autumn, disrupting the ripening process of cranberries and attracting buyers to the seductive red belatedly. Growers had to wait for the fruit to turn red, which made the harvest longer than usual. "Mid-September is usually harvest season, but it's now forced to be postponed to October," Wick said.
Climate change in other seasons can also affect cranberry growth. Every year, cranberries experience severe winter cold, but winter is getting less cold. Katherine Ghantous, a biologist at the University of Massachusetts Cranberry Station, says that while it's not yet irretrievable, the day when it's hard to meet cranberries' cold weather requirements may soon come.
Reduced snow and ice in winter also hampers other important measures to protect cranberries. Growers usually inject large amounts of water into the swamp in the winter, mainly to stabilize the temperature around the vines. Every few years, they would drive to the ice and sprinkle a layer of sand. When the ice melts, the sand falls gently between the plants below. "Sanding" can promote new root growth, burying harmful eggs and fungal spores, thus helping to ward off pests. Now, however, there are very few cases where the ice is thick enough to drive a car, forcing growers to pour plenty of water into the swamp, sprinkle sand with expensive mini barges, or walk up to the vines to spread sand, sometimes hurting the vines. Neither of these methods is good.
Massachusetts is the second largest producer of cranberries in the United States after Wisconsin. Most of the fruit is made into juice or dried cranberries, and only 5% is consumed directly.
Frost hazards
Ellwood and colleagues turned over records from a cranberry grower in Carver, Massachusetts, about 64 kilometers straight from the marshes of Eldridge. The grower carefully recorded when 10 percent of the cranberries bloomed each spring, which is when the spray of fungicides began.
Spring warming leads to earlier flowering times: 2 days earlier for every 1 degree increase in the average temperature in May. Spring temperatures in Massachusetts vary greatly from year to year, so it's not that the flowers are getting early. But if the temperature is warm, like 2010, the flowering time will be at least two weeks earlier, and it is likely to become more and more frequent in the future, Ellwood said.
Premature germination can endanger the flowers, because frost is likely to occur in New England, and a small frost can "destroy the flowers" and ruin an entire harvest. To protect cranberries, growers typically monitor the swamp 24 hours a day, sleeping in a nearby truck or trailer, waking up every few minutes to check it out. If the temperature is close to freezing, quickly turn on the sprinkler and pour a layer of water on the cranberries. As the water freezes, tiny amounts of heat are released, warming the buds and leaves and enveloping them in a protective, fragile ice sheath.
But as the seasons lengthen, so does the risk of frost. If the buds germinate prematurely in the spring, or if the fruit is still on the vine in the autumn, the cranberries can be damaged even if it is only a day of frost. The Cranberry Station even has a system that uses information such as temperature, condensation point, etc. to help growers predict frosts. But it only worked in the period from April 15 to the end of October. Peter Jeranyama, a plant physiologist at Cranberry Station, said that at the request of growers who had already seen climate change, he updated the forecasting system's working hours, adding two weeks each in the spring and autumn.
Climate-induced chaos
The Blue Mountains Meteorological Observatory, located south of Boston, has been tracking temperature changes for more than 130 years, making it the longest time span recorded in North America. Since 1885, the average annual temperature there has risen by 2.2 degrees, well above the global average of 1.1 degrees. Climate models show that temperatures will be higher in the future. According to the 2018 National Climate Assessment, temperatures across the Northeast are expected to be 2.2 to 2.8 degrees above the pre-industrial average in 30 years, by 2050; they will feel stronger at the rate at which the Blue Mountains and suburbs are developing.
Warming doesn't necessarily have a direct impact, but there are some linear relationships in the plant kingdom: rising temperatures are associated with early flowering times.
Plants that adapt to cold environments, such as cranberries, rely on winter dormancy to start a full year's life cycle, such as flowering; in the near future, Ellwood says, the most worrying thing is that they "may have no idea when to bloom because the seasons are already chaotic."
Other changes are more complex, but the impact is not small. In the northeast, for example, precipitation is changing rapidly. Every 1 degree increase in the atmosphere stores 7% more water, which means that precipitation is increasing.
This year, for example, the region experienced record-breaking droughts. But several major storms immediately brought more than a dozen centimeters of precipitation. Overall, precipitation was slightly lower than normal. But "plants can't absorb 12.7 centimeters of precipitation in 5 hours," Eldridge lamented, mainly because the land can't absorb heavy rain.
Theoretically, breeders could develop a new variety of cranberries that better cope with climate change to replace the ones they have today. The problem is that cranberries are perennials that growers can't afford to change varieties frequently, and some of Cape Cod's vines are over 100 years old.
For many growers, climate change is not the primary concern. But for Eldridge and others, the effects of climate change are becoming more apparent, and they hope people like Jeranyama will help them find ways to adapt. The system, he said, has a lot of flexibility; cranberries have evolved to encounter pressures from climate, and they have a certain degree of adaptability. Growers can use small tricks to control the temperature of the swamp, such as making it wet at critical moments (evaporation of water vapor takes away excess heat and cools the surface of the swamp; water ice releases heat, causing the swamp to rise by 5.5 to 11.1 degrees in a short period of time). But such adjustments require both manpower and money.
That means growers and researchers should start thinking about the future, Wick said. Today, "the southernmost point for growing cranberries is New Jersey." And by 2100, the weather in Massachusetts could be the same as in New Jersey today, or even further south, so what should we do? ”
(Translator: Sky4)