Climate Change Impacts and Projections for the Greater Boston Area: Findings of the Greater Boston Research Advisory Group Report

During the writing of the inaugural Boston Research Advisory Group (BRAG) report both NASA and NOAA announced that 2015 was the warmest year on record, beating the previous record set in 2014, by 0.29 °F. Just five years later (during the writing of this report), NASA announced that 2020 had tied 2016 for the warmest year, breaking the previous record by a stunning 1.84 °F, and that the last seven years have been the warmest seven-year period on record. These observations support the assertion made in the sixth and most recent assessment by the Intergovernmental Panel on Climate Change , which states, “It is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.” Hence, the question is not whether the climate is changing, but what we’re going to do about it. At a minimum, we must focus efforts to get to net zero greenhouse gas (GHG) by 2050. It’s not too late to achieve that goal, but time is running out for us to prevent the worst-case scenarios suggested here. This report is broken into four chapters and summarizes the most recent (as of late 2021) scientific understanding of climate risk factors pertinent to Greater Boston

Climate Change in Metropolitan Boston

Even though urban infrastructure systems are important and are designed according to socioeconomic and environmental conditions that are very sensitive to climate, there have been few major integrated assessments of the impacts of climate change on metropolitan infrastructure systems and services and possible adaptations. An analysis of the Boston metro area found that adaptation actions taken before full climate-change impacts occur will result in fewer expected negative impacts to the region than waiting for major impacts to occur. Adaptation of infrastructure to climate change must also consider land use management, environmental and socioeconomic impacts, equity, and adaptation actors and institutions. There are existing and additional policy instruments to encourage action

Climate Change Impacts on Groundwater in MAPC Communities

Groundwater is important for human health and the environment but has often been overlooked in the development of climate change adaptation strategies. This is because groundwater is rarely visible, and because changes in groundwater levels are not as dramatic as extreme flooding events, coastal storms, and storm surge. The importance of groundwater for drinking water, natural resources, and streamflow is well documented. Groundwater levels are also important considerations in the design of pavements, underground infrastructure, foundations, on-site wastewater treatment systems, and in the remediation of hazardous waste disposal areas. Groundwater is especially important in the wet northeast, where groundwater levels tend to be shallow and impactful. It is typically assumed that on average groundwater levels are not changing. This is no longer true with climate change. Groundwater is the world’s largest distributed source of fresh water and is important for both ecosystems and human consumption. Groundwater levels are affected directly by recharge (water infiltrating the ground surface and moving into the groundwater system) and water losses through groundwater discharge to surface water bodies and groundwater withdrawals from aquifers. Many factors influence the amount of groundwater recharge that occurs. These include precipitation, temperature, evapotranspiration, land cover and land use, soil moisture, and topography. Climate change is affecting the global water cycle by increasing rates of ocean evaporation, terrestrial evapotranspiration, and precipitation. Precipitation, temperatures, and sea levels are all projected to increase in the northeast due to climate change. These factors can result in long-term and seasonal changes in groundwater levels potentially impacting drinking water supplies, water quality, the useful life of pavements and underground infrastructure, and flooding

CLIMATE READY BOSTON: Climate Change and Sea Level Rise Projections for Boston, The Boston Research Advisory Group Report

This report summarizes the current understanding of the local factors that influence Boston’s future exposure to climate change risks. The following four risk factors were considered most relevant to Boston and are therefore evaluated in this report: sea-level rise, extreme precipitation, coastal storms and extreme temperatures. For each risk factor, a team of scientific experts, comprised of a team leader and three or more team members, was selected to evaluate and summarize the available information contained in both grey (reports, conference proceedings and the like) and peer-reviewed literature. Each team met independently between October 2015 and January 2016, and team leaders had regular teleconferences with the UMass Boston project team to keep them apprised of progress and to help overcome problems that were encountered. The process for reaching consensus is outlined in the next section

Preparing for the Rising Tide

On October 29, 2012, one of the largest Atlantic basin storms in recorded history hit the East Coast. Although Superstorm Sandy centered around New Jersey and New York when it made landfall, the massive storm system spanned 1,000 miles north to south, over three times the size of a typical hurricane. Luckily for Boston, Sandy’s storm surge hit the city near low tide, causing relatively minor coastal flooding. Had the storm hit 5½ hours earlier, 6.6 percent of the city could have been flooded, with floodwaters reaching City Hall. Events such as Superstorm Sandy highlight the growing relevance of climate change and draw attention to the importance of taking steps today to be prepared for the likely events of tomorrow. Preparing for the Rising Tide provides policy makers, planners and property owners with site-specific examples of how to assess vulnerability and increase resilience to coastal flooding over time. The United Nations Intergovernmental Panel on Climate Change (IPCC) defines vulnerability as the degree to which a system is susceptible to, and unable to cope with, adverse effects of climate change, including climate variability and extremes.” Vulnerability assessments focus action on highly sensitive populations, locations and infrastructure. Preparedness plans need to be robust enough to handle any future condition, and/or flexible enough change over time to meet needs as they arise. Ideally they include “no-regret” and co-benefit” solutions that extend beyond flood control goals. Cost-effective preparedness plans will result in both “here and now” and “prepare and monitor” actions based on threshold triggers such as sea level rise. Previous reports have described a range of large-scale adaptation strategies. This report takes those recommendations and applies them to specific properties in Boston. Some cities such as Seattle, WA and Charleston, SC are developing “floodable zones” that preserve the city’s access to its waterfront while minimizing damage when periodic flooding occurs. This concept of “living with water” is an option to consider in Boston as well

Implementing just climate adaptation policy: An analysis of recognition, framing, and advocacy coalitions in Boston, U.S.A.

Cities face intersectional challenges implementing climate adaptation policy. This research contributes to scholarship dedicated to understanding how policy implementation affects socially vulnerable groups, with the overarching goal of promoting justice and equity in climate policy implementation. We apply a novel framework that integrates social justice theory and the advocacy coalition framework to incrementally assess just climate adaptation in Boston, Massachusetts in the United States. Boston made an ambitious commitment to address equity as part of its climate planning and implementation efforts. In this paper, we evaluate the first implementation stage over the period 2016–2019 during which Boston developed coastal resilience plans for three neighborhoods. Despite Boston\u27s commitment to equity, we find injustice was nevertheless reproduced through representation and coalition dynamics, the framing of problems and solutions, and a failure to recognize the priorities and lived experiences of city residents. The assessment framework presented can be adapted to evaluate how other climate adaptation initiatives advance social justice and highlights the need for incremental evaluation over short time periods to inform ongoing implementation efforts

Evaluating Boston Harbor Cleanup: An Ecosystem Valuation Approach

In this study, we develop an economic evaluation of the Boston Harbor Cleanup, a court-mandated action started in 1986, through a comparison of cleanup costs and relevant ecosystem service values. Our results suggest that the ecosystems in the study area provide services to society with a capitalized value ranging from $30 to$100 billion. The $4.7 billion cost of the Boston Harbor Cleanup is about 5–16% of the total asset value of ecosystem services. Although it is not clear what fraction of the ecosystem value is due to the cleanup, our results suggest that the cost of the cleanup may be justified by our high- or midpoint-estimates of the value of ecosystem services

Integrated Analysis of the Value of Wetland Services in Coastal Adaptation; Methodology and Case Study of Hampton-Seabrook Estuary, New Hampshire

The present impacts from coastal storms and high tides grow significantly over time due to SLR even over the relatively short period to 2060. Hydrodynamic model simulations of storm surge with and without sea level rise scenarios show that although flooding and inundation increases with increasing subtidal forcing and higher sea level, dissipation of the tide and storm surge in the estuary channel somewhat limits the maximum inundation that might otherwise be expected in the back marsh areas. The estuary is dominated by high marsh, which lies high in the intertidal zone and by 2060 it will convert to mostly low marsh unless it can build very rapidly (greater than 5 mm/year). The marsh supports fisheries and many charismatic birds, some marsh dependent, and provides a culturally significant view-scape across the estuary. The Sea Level Affecting Marsh Model (SLAMM) was used to predict habitat changes due to 0.73 m SLR by 2060 under different accretion rates and levels of protection for developed areas that became intertidal. Although the relative amounts of high marsh and low marsh varied dramatically, the overall marsh area remained within 5% of the current levels and mostly increased if marsh accretion rates exceeded 2 mm/year. Limited areas of intertidal flats supporting shellfish exist in present day, but in the near future culturally important recreational shellfish areas will convert to open water. However, areas that are currently low marsh will drown and may provide future shellfish areas. The open water harbor is important for boating, access to coastal waters and recreational fishing. Currently, the open water area is small, but may double in size by 2060 and the greater tides relative to the marsh elevation will create a different feel for the estuarine landscape in the future because high tides will regularly cover larger areas of the marsh with seawater. Outside of the estuary on the oceanfront, beaches and dunes support tourism and intensive recreational use as well as federally protected nesting shorebirds (piping plover, least tern). Most of the outer beach is exposed to Gulf of Maine waters. Where there are existing floodwalls, rising sea levels will worsen the storm danger and damage to the integrity of the walls. Unless walls are raised, storms will also transport massive amounts of beach sediments over the walls and across the barrier system. Beaches will have less width and steep ramping to the walls will severely decrease the value of the beach for tourism. In areas with dune systems, very little change is predicted for this area because the dynamic equilibria of the dune-beach system will allow the beach to build in elevation as sea level rises and wind-driven dune building will continue. Bedrock outcrops (at Plaice Cove, Great Boars Head and the inlet) help reduce landward erosion. The socio-economic impacts result in more people flooded as sea level rises, particularly of socially vulnerable populations, and more anchor institutions flooded. Residents presently living in the most socially vulnerable census blocks were 8.6 times more likely to be located in the flood zone, compared to those living in blocks with low social vulnerability. Under climate change,census blocks with high percentages of the population living in poverty were 17.7 times more likely to be located in the flood zone. This analysis more likely reflects the winter/spring population than the summer population. The estimated annual expected value damages in the present are approximately $0.90 M. In 2060 with SLR they are$4.8 M. Using a 7 % discount rate, the present expected value of these damages between 2018 and 2060 is approximately $27 M. There are many sources of possible error in this value due to missing data, and not including damages to infrastructure, human mortality and morbidity, lost business (particularly recreation), and other cascading and multiplier events. We also do not include the value of ecosystem services. The adaptation goal focused on protecting the socio-economic systems of the barrier beach areas. Engineering approaches that only use hard structures or grey solutions may weigh the communities down with severe debt, result in long term damage to the environment and degrade the charm and attractiveness of the area to tourists. On the other hand, allowing over-wash and marsh migration everywhere will reduce the number of people and tourists that benefit from the beaches and dunes, shellfish flats, marinas, fishing and marshes. Because marshes of limited area do not significantly decrease storm surge and there is limited wave activity on the western, inland side of the barrier beaches, the marshes may not directly contribute to reducing the flooding on the western side of the barrier beaches. Regional solutions such as building a berm or a floodwall (smaller footprint limits direct marsh losses) to limit land loss will prevent marsh migration. Flood protection berms to protect all residential development bordering the estuary will result in significant marsh loss. Individual site flood management actions such elevating buildings must be employed there. The most expensive adaptations are needed on the coastal side where the beach-dune system has been replaced by an armored shoreline (seawalls) designed for pedestrians and automobiles, but not beach goers. These walls need to be fortified; their expansion opens an opportunity to provide alternate transportation pathways that are safe (bike lane), green space, and a more attractive promenade (increasing ecosystem/cultural services for residents and visitors). The beaches need to be nourished to provide sandy areas at high tide (especially in the northern areas) to better support the tourism industry. The two oceanfront sections without walls or dune systems were especially vulnerable; these could benefit from green adaptation solutions that construct and maintain sacrificial dunes at relatively low cost. Residential areas landward of existing dune fields were deemed the best protected and only required low cost adaptation decisions (e.g., building sand barriers at beach access cuts and maintaining dune health). Heavily used roads that cross marshes on causeways will need to be raised. Although more expensive, roadways elevated above the marsh surface will reduce impacts from direct filling and provide better tidal exchange. Thus throughout the HSE, there are limited reasonable green options for coastal flood management here. The present value adaptation costs in 2018 including capital and maintenance costs discounted at 7$149 M. This adaptation cost is more than the previously estimated damage avoided cost or benefit of $27 M. Because, as noted earlier, this benefit estimate is significantly underestimated due to data and methodological limitations, we cannot really state this project is not cost-effective; it actually may be cost effective. A lower discount rate would also increase it cost-effectiveness. Adaptation would mitigate some of the direct impacts to social vulnerable populations, but in some areas would require towns investing in the protection of their individual residents instead of being part of a possibly less costly regional solution. The adaptation plan could provide important public health benefits through the addition of the green elevated walkway (in place of current parkingspaces) along the floodwall. We met with several local non-governmental (NG) and mixed governmental and NG organizations over the grant lifetime. They generally support our findings. One possible troubling possibility is that 75As described above, the marshes themselves are not major contributors to present and future flood protection in the area. They are, of course, valuable for other reasons. Examples include habitat, runoff treatment, recreation, tourism, and carbon storage. An estimate of the annual values of these services in HSE are approximately$370 M under present and future SLR conditions. Thus, their preservation should be a priority