As seas rise, Boston Harbor islands listed among country’s most endangered historic sites

Ocean-borne dangers from the changing climate pose “the greatest and most immediate threat” to the islands, said Katherine Malone-France, chief preservation officer for the National Trust, a nonprofit organization based in Washington, D.C.

Erosion and storm damage, she said, “are both active and destructive to a broad range of historically significant places and sites on the islands.”

As ocean levels rise and storms intensify, once-formidable seawalls have broken apart. Historic sites such as Boston Light, the nation’s oldest lighthouse, and 19th-century Fort Warren on Georges Island are threatened. In addition, quickening erosion of the sand, clay, and cobble that comprise much of the islands has exposed human remains and coffins on Gallops Island, where smallpox victims were treated and quarantined.

For Native Americans, the damage is dramatically altering what has long been sacred ground.

“There may be Native American remains on the islands, but that’s not the only thing that makes them sacred,” said Elizabeth Solomon, an elder of the Massachusett Tribe at Ponkapoag. “What’s really important to us is they’re a place where we can interact with the spirit of our ancestors.”

The importance of the National Trust listing “is profound,” said Kathy Abbott, president of the nonprofit group Boston Harbor Now. “I hope this will bring attention to the issue and the need to get more people interested and involved. It’s going to take everybody to figure out what we need to do to address this.”

If trends continue, Abbott said, “the islands will be eroded and be reduced, and eventually they will be occasionally overtopped by storms. They will shrink in size and probably in height.”

Joseph Bagley, the archeologist for the City of Boston, said parts of some islands are eroding as much as 3 feet a year. The islands, a series of “drowned drumlins” left behind by receding glaciers, are unique in the United States.

“The islands are seen as these natural resources, but with that natural landscape is this human past that has existed that we are actively losing in every storm,” Bagley said.

Using a $100,000 grant from the city’s Community Preservation Committee, a team including Bagley, Native Americans, and others will assemble a “triage list” this summer of the most endangered sites on the islands as part of an archeology climate plan, Bagley said.

The need for protection, as underscored by the National Trust designation, is urgent.

“We know there are 103 archeological sites that have been found on the harbor islands, but there are likely many, many more,” Malone-France said. “They remind us of how intertwined our natural and cultural resources are, and we have to steward them together.”

An endangered listing from the National Trust does not carry additional protections for the islands, which are governed as a national and state park by a partnership of 11 agencies that include the city, state, and National Park Service.

However, the listing is meant as a call to action to mitigate the effects of climate change.

“I am thankful in some ways that this designation may help all of us to reckon more deeply with the choices of the past and the choices of the present,” said the Rev. Mariama White-Hammond, Boston’s chief of environment, energy, and open space.

In recent years, Boston has experienced more so-called sunny-day flooding than nearly any other coastal community in the country, according to a 2020 report by the National Oceanic and Atmospheric Administration.

In 2017, high tides inundated parts of the city on 22 days, a local record and more than any other community on the East Coast that year. In 2000, the number for Boston was six. NOAA defines sunny-day flooding as water that rises about 2 feet above typical high tide.

Malone-France said one factor in choosing the country’s most endangered sites are ongoing efforts to save them.

“We’re looking for sites that already have dedicated local partners who are fighting for these places,” Malone-France said. “And we’re looking for places that just don’t have threats but have potential solutions . . . that could provide a model for other historic places.”

Malone-France pointed to the archeology climate plan, one of the first in any city in the country. Boston and partner organizations also are engaged in an innovative project, funded by the Stone Foundation, to devise “nature-based solutions” to water-borne damage caused by climate change.

“These are engineered approaches that mimic some aspects of nature in trying to control a threat,” said Paul Kirshen, a University of Massachusetts Boston professor at the School for the Environment, who is director of the Stone Living Lab.

One example of a human-made, nature-based solution already exists at Clippership Wharf in East Boston, where architects designed a terraced shoreline with new salt marshes and rocky beaches behind a seawall.

The lab’s ongoing study of ways to mitigate coastal damage includes contributions by UMass Boston, the City of Boston, the National Park Service, and Boston Harbor Now. It’s a given that traditionally used buffers such as blunt concrete walls eventually erode, Kirshen said.

“Look at the way nature deals with flooding — soft surfaces, and they’re angled. They also have vegetation on them, and these absorb energy and provide habitat,” Kirshen said.

The Living Lab has established a monitoring station on Rainsford Island, but the construction of full-scale experimental structures will wait until the permitting process is complete.

In the meantime, the islands are losing ground. Although they erode and move naturally, Bagley envisioned a dramatically altered vista in the future.

“They’ll dance, but they won’t go away completely,” Bagley said. Even so, he added, “they’ll look radically different from the way they look today.”

Brian MacQuarrie can be reached at brian.macquarrie@globe.com.