Danehy: Drought and failed irrigation were fatal, and trees at the park aren’t out of the woods yet
An irrigation system at Danehy Park broke for more than a month during this unusually hot summer and its drought, bleaching grass and endangering trees over roughly half of its 55 acres in a city already found to be losing tree canopy at an alarming rate.
A count by alarmed residents spotted 17 dead trees among as many as 108 that looked stressed; the Department of Public Works identified nine trees as dead – though four of those were known to be dead before the auto-timed irrigation system stopped turning on in June, said Owen O’Riordan, commissioner of the department and acting deputy city manager.
The residents who did the tree count – environmental activist Charles Teague and Ruth Loetterle, a city manager appointee to the Committee on Public Planting and recently retired landscape architect – say the city could have done more, pointing to warnings dating back to at least 2016 to prepare for “predictable drought” and an extensive to-do list from the Urban Forest Master Plan summary released in February 2020 “of which a fraction has been implemented.”
Though temperatures have grown cooler and there have been several rains this month, a National Oceanic and Atmospheric Administration projection relied on by the city sees drought persisting at least into November.
Despite the breakdown of the irrigation system, it is these sustained drought conditions that O’Riordan blames most for the suffering trees.
“Charlie indicated something in the order [of 100-plus trees] that he saw as being impacted or stressed. And we wouldn’t disagree with that figure,” O’Riordan said in an interview Sept. 7. “We won’t know until spring of next year as to whether or not they have been impacted to the point where they need to be removed.”
Danehy Park, which is grown out of a layer of topsoil over landfill, has irrigation systems that are more than three decades old. The site was a clay mine, then a trash pit from 1952 until 1971 and an MBTA dumping ground until 1983, with the transformation into a park coming between 1988 and its opening in September 1990.
When a pump and piping in one of the two aged systems failed during the summer’s drought, the results were noticeable quickly – as city councillor Quinton Zondervan noted after attending the annual Jazz Festival: “All the ground is brown, all the grass is dead … one of the stands of trees in particular is in serious trouble.” But there were delays in securing material for irrigation-system repairs and to get a contractor in, and water didn’t begin flowing again until after the contractor arrived July 27, O’Riordan said. By then, the city was bringing in trucks to water the trees manually, and repairs took until August.
“At the outset, people were most concerned about just the failure of the grass itself, rather than its impact on the trees. But the longer the drought continued, the more concerned we became,” O’Riordan said. There were about 40 trees losing leaves in an alarming way, including red maples near the 4,000-square-foot Miyawaki Forest installed in September as an experiment to boost biodiversity and climate resilience. “It became obvious that the trees were struggling to an extent that I think surprised most of us.”
That’s not just about the irrigation failure, though, and not limited to Danehy Park, O’Riordan said: “We were surprised by the extent the more mature trees were impacted by the drought. We did a really good job in terms of watering the younger trees in the city, but surprised to see some of the more mature trees struggling to an extent that we hadn’t expected.”
Canopy report due
The impact of the drought led to a citywide call toward the end of July asking residents to water the trees in front of their properties. “We actually got a really good response,” O’Riordan said.
Teague expects to see more of that. Federal drought monitoring clearly shows the increased frequency and severity of droughts in Middlesex County when comparing the past decade to one from 2000 to 2010, and that this summer’s drought was worse even than those of 2016 and 2020, he said. City management spent large amounts of time and money creating “task forces” to study and report on climate change, he said, but the response to this one at Danehy and other parks “was late or non-existent despite a warning” from the city own tree task force experts.
During a more recent visit to the park, Teague said, many of the trees were seen to be blooming again – with a fall bloom being bad news, signaling a potential spring failure. O’Riordan’s take Wednesday on the current signs of recovery suggested agreement: “Our arborists would be hesitant to venture an overly rosy opinion of the trees’ likely health moving forward. We will need to see how they leaf out in the spring.”
At the least, the nine trees known to be dead by early September will need to be removed, O’Riordan said.
What happens to the Danehy trees – beginning with the nine dead ones – is too new to be counted in a report on the city’s tree canopy due imminently from the University of Vermont Spatial Analysis Lab. The report tracking what’s happened to the city’s tree coverage since 2018 was delayed on the university’s end and has been repeatedly put off. Last spring, the lab estimated that its analysis would arrive in mid- to late June.
In the previous report, residents were shocked to discover 11 percent of Cambridge’s tree canopy had been lost in the previous four years.