Palo Alto famously loves its trees — as its namesake redwood, its official seal and its recently adopted Urban Forest Master Plan loudly and proudly testify.

But despite that passion, city laws that protect local trees are somewhat weak and outdated, a conclusion that residents and city staff reached more than three years ago, when they began an effort to update the city code. Planning staff struggle with the ambiguities in the city's code, particularly its failure to address situations where trees impact accessory dwelling units or neighboring properties. Neighborhood leaders argue that the laws are too permissive when it comes to allowing developers and property owners to remove trees as part of construction projects. City commissioners observe that other cities protect a wider array of trees than Palo Alto.

Bryna Chang, a member of the city's Planning and Transportation Commission, said she was surprised to learn recently that Palo Alto's tree protection laws are weaker than in neighboring cities.

"I was absolutely shocked that despite the great pride we take in our trees and the great pride we take in being a green and environmentally conscious community, we protect our trees far less than all of these neighboring cities," Chang told the City Council on Monday, as the council considered its first update of the tree protection ordinance in 20 years.

She was one of about two dozen residents, including environmental advocates, nonprofit leaders and neighborhood activists, who supported stronger protections. Some touted the environmental and health benefits of trees, particularly when it comes to sequestering carbon, supporting biodiversity and keeping neighborhoods cool. Almost all urged the council to expand the city's tree protection laws to be more aligned with surrounding jurisdictions.

"As a resident of Palo Alto, it has been disturbing and heartbreaking to see residential lots in my neighborhood stripped of all vegetation, including beautiful large trees, prior to new home construction," Julianne Frizzell, a landscape architect who lives in Palo Alto. "Aesthetically and ecologically, removal of trees has a negative impact on neighbors, neighborhoods and the community."

While cities such as East Palo Alto, Redwood City, Sunnyvale list all species as "protected" once they reach a certain size, Palo Alto tree protection laws protect just three native species: the coast redwood, the coast live oak and the valley oak. According to the city's Urban Forest Master Plan, there are about 534 coast live oaks, 243 coast redwoods and 215 valley oaks in the public right of way, making these three among the most common city-owned native species in the city (that said, they are far outnumbered by imported species in the street-tree population such as the southern magnolia, which number more than 4,000 in Palo Alto; the city also has 2,832 London planes and 2,669 liquidambars).

Among the code changes that the city has been contemplating was expanding the roster of protected trees to more of the 22 native species that are listed in the master plan -- a list that includes the bigleaf maple, the California incense cedar and the California bay. The revised approach proposed by the ad hoc committee, which includes former Mayor Karen Holman, Parks and Recreation Commission Vice Chair Jeff Greenfield, planning Commissioner Doria Summa and community activist Winter Dellenbach, calls for designating as "protected" the two oak species that are currently listed as such and adding to the list the bigleaf maple, the California incense cedar, the blue oak and the California black oak, as well as the coast redwood.

Significantly, the revision would also lower the size threshold for protected trees. Public works staff has initially proposed protecting all trees that have trunk diameters of 36 inches or greater, while keeping a lower threshold for three native tree species that currently enjoy protected status: 18 inches for the coast redwood and 11.5 inches for the other species. A change proposed by an ad hoc committee called for a diameter threshold of 11.5 inches for native tree species and 18 inches for all other trees. Holman, who now serves on the board of directors at the Midpeninsula Regional Open Space District, urged the council on Monday to move ahead with the various revisions.

"With one action tonight, the council can positively influence more aspects of life in Palo Alto than virtually any other single action you can take," Holman said.

Various environmentalist nonprofits, including Canopy, the Sierra Club and the Santa Clara Valley Audubon Society also lobbied the city to strengthen its tree protection laws. Canopy noted in a letter that neighborhoods with street trees can be up to 6 to 10 degrees cooler than those without. Trees, Canopy argued, provide "a substantial return on investment and, even in times of drought and budget tightening, are worth their water and maintenance."

"The reasons for protecting and planting trees are clear," states the letter from Holly Pearson, a board member at Canopy, and Catherine Martineau, the nonprofit's executive director. "Among many other benefits, trees sequester carbon, combat the urban heat island effect, cool buildings, prevent soil erosion and stormwater run-off, provide wildlife habitat, and promote walking and biking on city streets."

While the council stopped short of formally adopting the code changes on Monday as many had urged, it sent a clear signal that major revisions are coming soon. Over a series of votes, the council directed staff to move ahead with an ordinance update that would reflect a host of revisions that align with recommendation from the ad hoc committee ofand its Policy and Services Committee, which reviewed the proposed changes in August. And in moves that further aim to raise the profile of local trees, the council also voted to elevate the urban forester position within the department and to designate the Parks and Recreation Commission as a forum for tree-related discussions.

In addition to broadening the list of protected species, the revision effort would introduce several other new policies. One aims to address what staff called a "loophole" in the code -- the more stringent requirements for removing trees as part of a development proposal than for cases not involving new construction. This creates an incentive for developers to remove trees in advance of an application, said Peter Gollinger, the city's acting urban forester. To address that, the add hoc group and the Policy and Services Committee proposed a 36-month moratorium on development for any property that removes a protected tree.

Another revision creates an appeal process for instances in which a protected tree is proposed for removal in the absence of a development application. With the change, the person removing the tree would have to notify all neighbors and property owners within 600 feet of the property in writing about the tree removal. Everyone within 600 feet will have the option of appealing the removal.

The revised ordinance will undergo reviews in the coming months by the Parks and Recreation Commission and the Architectural Review Board before returning to the council for approval in March or April. Mayor Tom DuBois and council member Lydia Kou both supported a faster timeline but ultimately acceded to the process laid out by staff, which includes additional outreach to the broader community.

"Proposed changes like significantly expanding the categories of protected tree species could potentially impact many or even most properties in the city," Public Works Director Brad Eggleston told the council. "While we know in our outreach process we never manage to reach everyone who might be interested, we do want as much as possible to avoid people being surprised when they learn that an existing tree on their property has become protected and that impacts what they're allowed to do."

Some council members supported a more deliberate approach. Council member Greg Tanaka wanted to know more about the costs of adopting and enforcing the new laws, as well as of raising the urban forester position in the City Hall hierarchy (he was the only council member who voted against elevating the position). Council member Alison Cormack also supported more outreach and analysis before deciding on expansion of the list of protected species. She and Tanaka both opposed DuBois' motion to modify the definition of "protected trees" to include any tree at least 15 inches in diameter (despite their opposition, the provision passed by a 5-2 vote).

"I am absolutely open to adding species to the list and potentially reducing the size of the diameter, but I am not comfortable this evening making those decisions," Cormack said. "I don't feel we've been presented with enough information to be confident in making those decisions."

Others favored faster action on what they characterized as a critical issue. While Cormack asked her colleagues what problem the city is trying to solve with the code changes, Vice Mayor Pat Burt noted that it's "not a single problem and it's not a single benefit."

"That's one of the great things about this," Burt said. "We simultaneously address noise and heat and air and water pollution and aesthetics and climate impacts and the natural habitat — even slowing of traffic."