City of Palo Alto tree ordinances state that, under certain conditions, trees that have been removed must be replaced.
Protected trees: If the city authorizes removal because the tree is dead, dangerous or a nuisance, no tree replacement is required. In all other cases, the tree must be replaced.
Designated trees: The director of Planning and Community Environment or a designee decides on the number and nature of replacement tree(s) based on the value of the removed tree. The value is determined based on the "Guide for Plant Appraisal" published by the Council of Tree and Landscape Appraisers.
Street trees: If the city authorizes removal of a street tree in connection with a development project, the city must specify replacement requirements in the permit that authorizes approval.
When trees cannot be replaced on site: The value of the tree is calculated under the city's Tree Value Replacement Standard. The money is used to either provide additional trees elsewhere on the site; add street trees or other public landscaping nearby; or add trees or other landscaping to other city property.
Species of tree replacements: When a protected or designated tree is replaced, the new trees must be of the same species unless the director of Planning and Community Environment determines that another species is more suitable for the location. Factors considered include long-term tree health, location, compatibility with surrounding uses and design.
Source: City of Palo Alto Tree Technical Manual