Editor’s note: This article is the third in a series exploring the impacts of climate change on three of Harvard’s key natural resources—and the policies that may be used to improve resiliency. Agriculture is the community’s economic base; Bare Hill Pond is a hub of recreational activity and an indicator of ecological health; forests contribute to climate change mitigation through natural carbon sequestration and storage. Each of these natural pillars faces challenges as a result of a warming climate and changing weather patterns that are especially pronounced in New England. By identifying these challenges and the plans that are already underway to address them, this series aims to provide a local perspective on climate change and its trajectory.
Forests and wetlands—which are key to sequestering carbon—account for about 72% of Harvard’s land area and make the town a powerful player in the regional fight against climate change. But rapidly changing weather patterns, paired with increased pressure from development, are leaving these resources vulnerable to an onslaught of new stressors.
Harvard is one of the better-resourced towns in an area where land-use composition varies widely. Only 13% of its land is developed, compared to 38% in neighboring Devens and about 50% in Ayer. According to Harvard’s master plan, over 25%, or about 3,862 acres, of land is protected through government ownership or conservation and preservation restrictions. Another 2,638 acres are privately owned and temporarily protected by Chapter 61, a state tax program that disincentivizes development (see “Chapter 61” below). These protections are especially important for maintaining forests and wetlands, which account for most of this area and work in tandem as sources of habitat, water management, clean air and water, and carbon sequestration.
Forests and wetlands are an environmental dynamic duo, and while each plays a unique role in maintaining the ecosystem, the two work so closely they are not always separable. Forested wetland—areas where trees and vegetation grow in soil that is saturated with water for some portion of the growing season—make up 11% of Harvard’s land cover. (See “Wetlands defined” below.)
Tracking water as it moves through the ecosystem illustrates this close-knit relationship. The Massachusetts Forest Action Plan—a compilation of assessments and strategies for keeping the state’s forests healthy and intact from the Department of Conservation and Recreation—describes the hydrologic cycle. In forested areas, tree cover and brush change the way precipitation enters the system. Then, debris, such as leaves and branches, that blankets the ground filters water, creating more moderate soil temperatures, reducing evaporation, and slowly filtering nutrients into the soil below.
Bacteria in the soil then help to control nutrient loads that are passed on to surrounding habitats, serving as a filter between runoff and bodies of water, including wetlands. Water that reaches wetlands is further filtered. The Apple Country Natural Climate Solutions Report—part of a regional project to prepare for climate change using nature-based resiliency techniques—refers to wetlands as “landscape-level kidneys,” filtering pollutants from flooding events so that cleaner water is passed on to surrounding ecosystems. This process is especially important for maintaining clean drinking water.
Bob Douglas, a Harvard Conservation Trust trustee and conservation director for a neighboring town, outlined another crucial role of wetlands. Like a sponge, these areas take in water during floods or other high-water events, and exude moisture to surrounding areas during droughts and dry spells. The apple country report says that wetland vegetation has a cooling effect on water temperatures in connected bodies of water. Colder water supports a higher level of dissolved oxygen, which is vital to aquatic life and can reduce the likelihood of algae blooms.
“Wetlands are super important in Harvard and everywhere else,” said Douglas, referring to them as the “birthing area” for many species. Douglas said the town’s wetlands are home to several endangered species, including the Blanding’s turtle and blue-spotted salamander. He said that Harvard is the northeasternmost location where marbled salamanders—a species that is threatened in Massachusetts and endangered in several other states—have been seen.
Wetlands also play an outsized role in carbon sequestration. In Harvard, wetlands account for 19.9% of total land area and hold 29.3% of the town’s total soil organic carbon, about 393,750 metric tons. Douglas added that this is one important reason to protect wetlands. “If they are destroyed, if they’re allowed to dry off for a year or more, they’ll die and all that carbon can come back into the cycle.”
Forests are carbon sinks as well, meaning they take in and store more carbon than they produce, thus lessening some of the effects of emissions from human activity. In the Northeast, forests sequester between 12 and 20 percent of emissions each year, according to the forest action plan. This is dependent on many factors, particularly the age and type of forest.
Despite being forces of climate-change mitigation, both forests and wetlands are suffering the consequences of evolving weather patterns as well as increasing pressure from development.
Climate-related threats to Harvard’s forests are similar to those that challenge orchardists in the region. JC Ferguson, Harvard’s tree warden, said that increases in drought, pests, and disease have all come together to weaken forests in recent years. The Apple Country Climate Report identifies changes in land use—such as the conversion of forests to lawns—and invasive species as the two most disruptive stressors for Harvard’s forests in the face of climate change.
As the Massachusetts climate begins to more closely resemble that of southern states, its ecology will, too. Non-native species will begin to find the New England climate desirable, and creep upward, competing with increasingly stressed native species.
While climate change has increased overall precipitation in New England, according to the Massachusetts Wildlife Climate Action Tool—a collaboratively developed climate policy resource developed by the Massachusetts Climate Adaptation Partnership—droughts are also expected to become more frequent and severe. This is because additional rainfall is expected to come in the form of extreme precipitation events. Significant dry and wet spells are both bad news for forest health.
“Trees need water to survive,” said Ferguson, comparing them to the human body. “If you get stressed out, your immune system starts going down and your natural defenses are weakened, and you’re more susceptible to getting sick or not feeling well.” Trees, he said, are the same way, becoming more vulnerable to pests and disease during periods of drought.
Ferguson remembers the loss of a large oak tree that stood in the town center last year. It was uprooted in October after an especially wet summer. He theorized that the tree, which he estimated to be about 150 years old and appeared to be healthy above ground, could not manage the amount of water that collected around its root system. With 21 days of rain that July, he speculated that water collected in a natural ledge swale around the base of the tree. “It couldn’t drink quick enough,” he said. When the tree fell it exposed an entirely rotted root system.
Heavy rains last summer rotted the roots of this large oak on the Common, causing it to fall. The tree fell after an especially wet summer caused water to collect at its base. (Courtesy photo)
To add to precipitation-related stress, a warming regional climate is accommodating new varieties of pests and giving native pests a longer temperate season to do damage. Emerald ash borers—a non-native beetle originating from eastern Russia and Asian regions—have been detrimental to ash trees.
According to the UMass Extension Landscape Nursery and Urban Forestry Program, the beetle was first detected in Massachusetts in 2012 and has since spread through the state. Larvae from the ash borer are responsible for most of its damage, feeding on the tissue beneath the bark, and killing trees in one to four years. “I spend a decent amount of the tree-warden budget on tree removal and a lot of times those are ash trees that are completely dead from this pest,” said Ferguson.
Similarly, the hemlock woolly adelgid—an aphid-like insect originating from Asia—has moved north and become an issue for Massachusetts hemlocks. Most active during the winter, the pest feeds on the trees’ sap as they mature. Ferguson has seen many trees defoliated by adelgids, but they can also kill trees in a matter of years, particularly in regions where hemlocks are stressed. Ferguson said the insects are a relatively new threat to trees here.
Inconsistent winter weather patterns are also damaging trees. On unseasonably warm days, Ferguson said, “the trees kind of get tricked into, oh, it’s time to wake up. And they start trying to drink water and come alive.” In some cases trees may even begin to bud. Then, when the weather drops again, they become stressed.
Ferguson also pointed to more severe wind storms as a result of climate change. This can cause trees to break or uproot, which he said has been the case for some trees in town.
Chris Ryan, Harvard’s director of community and economic development, is concerned about maintaining comprehensive forest management and conservation. Where and how trees grow is important to the value they bring to a region, and Ryan said that much of Harvard’s forests are privately owned, creating a “checkerboard” of differently managed areas and inviting fragmentation. Fragmentation changes the kind of habitat that is available and tends to result in more forest edges, which function differently from inner forest areas. “That edge creates, in some sense, a barrier to the functionality of true forest,” he explained.
Forest edges are not without merit, though. “It depends upon the species of interest and the needs of an individual type of animal,” explained Ben Urquhart, a trustee of the Harvard Conservation Trust. He pointed to the ruffed grouse—a nonmigratory bird that has suffered significant climate-related habitat loss—and white-tailed deer as species that inhabit border areas, making use of both open land and forested spaces and, thus, benefitting from more forest edges.
Warming temperatures may even impact the aesthetic value of forests. New England is known for its spectacular fall foliage, but the color mosaic that emerges each year has already been shifting due to climate-related tree stress. According to the Harvard Forest—a long-term ecological research site funded by the National Science Foundation—white pines and chestnuts have suffered significant declines in the past century, resulting in a denser, redder treescape. Currently, hemlocks are becoming less common due to pests. Black birch are most likely to replace these trees, turning areas of deep green to shades of yellows. Most impactful to the visual appeal of the region’s forests is the likely northward shift of sugar maples, which prefer a cooler climate and also account for the most striking leaf coloring.
Development is one of the greatest threats to wetlands in the United States. Nationally, wetland loss in the 21st century has been significant, with over 600,000 acres lost between 2004 and 2009. Massachusetts stands out from the rest of the country, having gained wetland area in recent years, mostly through the creation of marshes and commercial cranberry bogs. Human activity in the state destroyed 1,548 acres of wetland, but added 2,733 acres, with residential and commercial development as the main drivers of losses, according to the Apple Country report.
One reason for this difference may be the Massachusetts Wetland Protection Act, which is one of the strictest wetland-protection codes in the country. The state law requires developers who destroy a wetland to replace it at a one-to-one ratio. Harvard’s bylaws are even more restrictive, mandating that those who file a notice of intent requesting to fill in a wetland for development must replace twice the area. In the case that a wetland is lost to a violation, it is restored back to its original area, unless otherwise agreed upon, according to Harvard’s land use administrator and conservation agent, Liz Allard.
Even laws that require wetland replication may not ensure that their ecological value is maintained. This is because new and human-created wetlands function differently from older natural wetlands. According to the Apple Country report, “newly created freshwater wetlands, such as cranberry bogs, or wetland replication areas, release more carbon … than they sequester for decades, centuries, or thousands of years.” Saltwater wetlands are quicker to achieve net carbon sequestration, and restored wetlands can return to their previous functions in a relatively short amount of time as well.
Ryan said that, while the town does not have as many large-scale development projects as some areas, small changes to private residential properties can add up. Property owners who clear their land or add impervious surfaces without considering resource area boundaries are “just death by 1000 cuts,” he said.
While development is a major threat to wetlands, Douglas identified a few climate-related challenges that could exacerbate their loss. Extreme precipitation events can drown wetlands and extended drought conditions can be even more harmful. “Wetlands are known to be resilient, but they can only take the drying for … a relatively short period of time.” If dry conditions stretch over several years, he said, it becomes difficult for wetlands to rebound. This can be particularly problematic when wetlands are home to endangered species.
Given the threat of wetland and forest loss due to the combined effect of climate stress and development, many of Harvard’s experts agree that conservation and management policies are key to their future health.
Ferguson said that when the town plants new trees, it may need to consider varieties that are tolerant of warmer weather and resistant to certain diseases. For Urquhart it’s about managing development through zoning laws and other municipal legislation. He also noted the importance of having funds set aside to take advantage of conservation opportunities as they arise, “Harvard looks the way it does today, in part, because of active preservation efforts by past generations.”
The Environmental Protection Agency defines wetlands as “areas where water covers the soil, or is present either at or near the surface of the soil” for some or all of the year. Many wetlands, such as vernal pools, are not actually wet year round, but serve a vital role in the ecosystem regardless. These areas are connectors between land and water and house diverse networks of aquatic and terrestrial flora and fauna. Wetlands are broken into two broad categories. Coastal, or tidal, wetlands are found along the coastline and are a mix of salt and freshwater. Inland, or nontidal, wetlands are found farther from the ocean, commonly in floodplains or otherwise near bodies of water. In the U.S., these two categories are further broken down to encompass four main types of wetlands: marshes, swamps, bogs, and fens. In Harvard, swamps and marshes account for the majority of wetland area. Local, state, and federal law all protect designated wetland resource areas, requiring developers to apply for permission before converting a wetland and often ensuring the land is replaced by an area of equal or greater size.
Climate change, forest edges, mature trees
While studies of tropical forests led a narrative of forest edges as less productive and resilient, new information from researchers out of Boston University shows forest edges in temperate regions to be highly valuable. Science writer Jessica Colarossi explained the findings in an article for The Brink, a news site disseminating pioneering research from the university. Edge trees have less competition and, thus, get more sunlight than interior trees, allowing them to grow faster. The faster a tree grows, the more carbon it takes in. However, rising temperatures resulting from climate change could slow tree growth, stunting this effect. In rural areas, soil at forest edges is warmer than interior soil, speeding the rate of decomposition as well as carbon dioxide release. In urban environments, hot dry conditions slow this same process, meaning these areas are particularly effective carbon sinks. Both trees and soil at forest edges may be especially vulnerable to extreme conditions, especially heat and drought, as climate change progresses. In addition to location, a tree’s size dictates its carbon storage capacity. An infographic from the Apple Country Natural Climate Solutions Project shows that a single mature canopy tree stores the same amount of carbon as 35 young canopy trees, 151 “typical street trees,” or 465 new large landscape trees.
Chapter 61: Privately managed, temporarily conserved
In 2016 Harvard had 694 acres of land temporarily protected by Chapter 61 of Massachusetts general laws. Chapter 61 is a state tax program meant to promote land conservation. By default, landowners pay taxes on their property based on its “highest and best use,” typically read as its development value. Under Chapter 61, owners pledge to leave their land undeveloped for a specified length of time in exchange for a lower tax rate. Chapter 61 is separated into three parts: Ch. 61, relating to forests; 61A, relating to agriculture; and 61B, for open space and recreation. In total, Harvard had 2,638 acres of land protected by the tax program in 2016. To qualify, forested areas must be at least 10 acres, minus the area used for a home, and be managed under a 10-year state-approved management plan. This land is taxed based on its forestry use, with values determined by the state-appointed Farmland Valuation Advisory Commission. The land remains under Chapter 61 even if it is sold. If a landowner wants to change the use of their land or sell to a developer, the town has the right of first refusal. This means it can purchase the land at full market value—if being converted but not sold—or match an offer—if being sold—and obtain the land. This land can still be developed. According to the town’s master plan, “it is common practice for land owners to remove their land from the program, pay back taxes, and carve the tract up for new development.” While the town occasionally takes advantage of its right to first refusal, the plan states that it will not be able to preserve most of the land that is removed from Chapter 61.
Lily Robinson will graduate this spring from the University of Massachusetts Amherst with a master’s degree in public policy. She has reported for the Press, first as an intern and then as a freelancer, since the summer of 2020.