County of San Mateo Protected Tree Ordinance
Protect Our Trees, Preserve Our Future
About the Ordinance
This website is intended to assist applicants, arborists, developers, interested members of the public and County Staff to guide decision making when using San Mateo County’s Protected Tree Ordinance. Information provided within this supplementary document is based on current best management practices in the Arboricultural industry and is subject to amendment as industry best practices are updated.
The Benefits of Trees
Trees are an integral part of our natural suburban and urban ecosystems. Their leafy canopies provide shade, which helps reduce temperature in the vicinity to help cool residential structures during hot summer months, intercept rainfall during winter which can reduce sudden localized flooding events, and they absorb carbon dioxide which helps clean our air. The figure below represents some of the many benefits of trees.
Cleaner Air
100 trees remove 53 tons of carbon dioxide and 430 pounds of other air pollutants per year.
Combats Climate Change
By reducing carbon dioxide, trees and vegetation directly combat climate change and air pollution.
Captures Rainwater
100 mature trees can capture and store about 139,000 gallons of rainwater per year.
Cleaner Water
A medium-sized tree can intercept up to 2,380 gallons of stormwater runoff per year.
Improves Public Health
People are less likely to be hospitalized for asthma when they live in neighborhoods with many trees.
Saves Energy
Strategically placed shade trees can help save up to $6 on annual air-conditioning costs for homes and businesses.
Reduces Urban Heat Island Effect
Shaded surfaces may be 20-45°F cooler than peak temperatures of unshaded areas.
Increases Business
Shoppers spend 9-12% more for products in shaded business districts and visit more frequently.
Green Economy
In 2009, urban forestry supported 600+ jobs in California resulting in $18.3 million individual income.
Improves Mental Health
People living in neighborhoods with less than 10% tree canopy are more likely to report symptoms of depression, stress, and anxiety.
Which Trees are Protected?
The following guidelines outline the protections in place for trees within the county. These regulations ensure the preservation of trees with significant trunk diameter, species with cultural and ecological importance, and those designated for specific conservation purposes. Understanding these protections helps maintain our community’s natural beauty and environmental health.
- All trees with a diameter of 12.1” when measured 4.5’ above grade are protected, unless otherwise specified in the exemptions section of the tree ordinance.
- Certain species of trees indigenous to the County have greater protections due to their cultural and ecological value.
- Heritage Trees designated by the Board of Supervisors.
- Any tree that was required by the County to be planted as a replacement tree, or protected trees retained by the terms and conditions of a development application, building permit, subdivision approval, tree removal, or code enforcement action.
- A community of trees.
- Any tree designated for carbon sequestration and storage and/or environmental mitigation purposes as identified in a permit or agreement between the property owner and a responsible government agency, where the County is a party or a third party beneficiary, or recorded as a deed restriction.
View our resources section for information on tree management.