Tree Canopy Update & 10/15 Policy Order

Tree Canopy Update & 10/15 Policy Order

The Urban Forest Master Plan Task Force was formed earlier this year, as a result of advocacy by myself, Vice Mayor Devereux, and Green Cambridge, and has been charged with advising in the creation of a master plan for Cambridge’s urban forest. The group has been meeting for a few months now and recently held a public meeting to discuss their findings to date. One of their first tasks was to look at the existing state of our urban tree canopy. Preliminary results from the April 2018 LiDAR flyover show that Cambridge has experienced a shocking 18% relative canopy loss since 2009. This means that there is 18% less land area covered by tree canopy today than there was in 2009. Perhaps even more troubling is that the rate of loss actually increased in recent years, jumping from a 7% decline between 2009 and 2014 to an 11% decline between 2014 and 2018. In light of this disturbing information, I will be renewing my call for more immediate interventions by the administration while the task force continues to deliberate through next Spring.

Depicts the canopy change by land use type. All categories show a net loss, but Residential is by far the biggest: we lost 171 acres of residential canopy but replaced only 82 acres.

The preliminary report shows that there has been a net canopy loss across every single land use category, including public open space, though residential areas are by far responsible for the greatest overall loss (not surprising as this is the majority of our land area). We lost 171 acres of canopy on private residential land, but added just 82 acres of new canopy through growth and new plantings. That means we would have to nearly double our planting rate in order to simply break even. It is reasonable to conclude from the report that the choices we are making around development and construction, in particular on residential land, are a major driver of the astounding canopy loss we have seen. Clearly, any serious solution to this crisis will have to involve both the planting of new trees AND the mitigation of future loss. Unfortunately we already have baked into our plans significant additional canopy destruction, including at the 14-acre site of the Volpe Transportation building which will be redeveloped by MIT over the next decade or so, and at the former site of Abt Associates, where many large trees are slated to be cut down to make way for new housing. Our current Tree Protection Ordinance does not require that the canopy loss be mitigated, allowing developers instead to pay into a tree fund, which is slowly spent by the city and obviously has not managed to increase canopy coverage. Developers can avoid even that minimal level of compensation to the city by cutting down the trees on their property a year and a day before applying for their construction permits.

Heat Map of Canopy Loss in Central Square from 2014-2018

These protections currently in place for trees on private land in Cambridge are clearly very weak, but there is precedent around the country and indeed in our own backyard for a stronger ordinance. Austin, Texas protects any healthy tree within city limits that has reached 19 inches in diameter. Oakville, California does the same, but for any healthy tree greater than 5.9 inches in diameter. Here in Massachusetts, the city of Newton protects private trees greater than 8 inches in diameter in certain circumstances. All three cities have implemented a permitting process for property owners who insist on cutting down a healthy tree of significant diameter.

I proposed a similar requirement for a permit1 to cut down any tree over 8 inches in diameter last June through a policy order to amend the current ordinance. The Council voted 5-4 to give the proposed amendment a hearing in the Ordinance Committee. Unfortunately, that hearing has not happened yet while we continue to lose more trees everyday. If we are serious about stopping the bleeding, we cannot afford to wait until next Spring when the task force is expected to finish deliberating. That is why I’ve submitted another policy order this week calling again for a hearing on my amendment, as well as a hearing on the canopy issue in general.

Policy order submitted to the 10/15/18 regular meeting by Councillor Zondervan

I asked my constituents what they thought of this proposal in an informal poll earlier this year, and 164 Cambridge residents responded to the survey, with 62% saying they are in favor of requiring a permit for cutting down healthy, mature trees on private property. Nobody denies that trees are our urban allies: crucial in stormwater management as well as important protectors against the urban heat island effect and polluted air. Trees are beneficial to everybody, even when they are located on private land. Unfortunately, the report indicates what we all suspected: lower income residents tend to live in areas with less tree canopy coverage. This means that the most vulnerable residents of our city will be the most adversely impacted by canopy destruction. This is a fundamental issue of social justice that must be addressed, and that means planting more trees in those areas. Trees are not just for rich people, and indeed we should be grateful for all the trees that property owners plant and protect, because they benefit all of us. The city has a heavily underused “back of sidewalk” program to plant trees on private property at public expense. We need to find better ways to utilize this program to achieve a more equitable distribution of trees on private land in our city.

Going forward we need to seriously consider how to develop our city and grow our canopy at the same time. Fortunately there are plenty of existing parking lots and low rise buildings that could be converted into both housing AND green space, creating further opportunities for canopy expansion. There are also new building techniques that allow for trees to be more directly integrated into the building, and not just on the roof. As climate change worsens we will need our tree canopy more than ever. Please join us in protecting and growing this valuable resource.

How to make your voice heard: If this issue is important to you one way or another, please write the council and let us know what you think! You can email all nine councillors at once: <[email protected]>. Please also include the City Manager’s office: <[email protected]> and the clerk (so it is entered into the official record) <[email protected]>. You can also submit written comments to the Clerk’s Office at City Hall during regular business hours. As always, if you’d like to reach me specifically you can email me at: <[email protected]> or call my office: (617) 349-9479. I look forward to hearing from you!


  1. The permit would be issued without a hearing and wouldn’t necessarily require a fee; emergency situations would be exempted. The point is not to get in the way of a homeowner needing to remove a dead or diseased tree, but rather to alert the city to large scale tree removal in the hope it can be avoided or reduced in extent.



3 thoughts on “Tree Canopy Update & 10/15 Policy Order”

  1. My escalating concern is not surprised by the report findings, just by walking in Cambridge it is evident…dwindly street trees, massive construction everywhere, sewer/gasline root impact, storms, higher wind gusts, frequently heard trunk/limbs grinding through chipper machinery. We need to launch an intensive recovery canopy & then a preventative additional “buffer” canopy for the calculated increases in global temperature and local storm/wind changes to come. The root systems will need to be mature as fast as possible to help with flooding as well. Let’s do it!!

  2. Urban redevelopment influences urban forests, with consequences for ecosystem service provision. Better understanding the effect of redevelopment on trees in cities can improve management and inform policy, thus having positive effects on ecosystem service provision and human wellbeing. This study quantified the effect of residential property redevelopment on canopy cover change in Christchurch, New Zealand. By applying an object-based image analysis (OBIA) technique to aerial imagery and LiDAR data, this study delineated tree canopy cover city-wide in 2011 and again in 2015 and then spatially quantified changes in city-wide canopy cover between 2011 and 2015. Changes in tree canopy cover were also determined at a finer scale, that of the meshblock, a geographic boundary used for census purposes. The results show a small absolute magnitude of city-wide tree canopy cover decline, from 10.84% to 10.28% between 2011 and 2015, but a statistically significant decrease in meshblock-scale mean tree canopy cover. Tree canopy cover losses were more likely to occur in meshblocks containing properties that underwent redevelopment, but the loss was insensitive to the density of redeveloped properties within meshblocks. These findings show that property redevelopment is an important influencer of urban forest dynamics.

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