The terms "tree banking" and "tree bank" are sometimes used in tree ordinances. The terms have an appealing ring to people who are interested in conserving tree resources because of the mental images they conjure up. However, these terms do not have a single, widely-accepted definition either as used in ordinances or as used in the wider world of forestry.
In tree ordinances, the term "tree bank" almost always refers to what is more generically termed off-site mitigation. Many city and county tree ordinances require tree planting, most commonly to replace trees that have been removed or damaged during site development and/or construction. In some cases, tree planting may be required to meet overall tree canopy cover or density standards in areas that have little or no natural tree cover. If it is not possible to plant all of the required trees on the parcel that triggers the planting requirement some type of off-site mitigation (i.e., "tree banking") may be required.
"Tree banking", as the term is most commonly used in tree ordinances, generally comes down to one of the following off-site mitigation tactics:
1. Planting trees in off-site mitigation banks, i.e., areas set aside
as a permanent receiver sites for tree plantings. The mitigation bank
is typically public land, although this would not need to be the case, and may
or may not have existing tree resources. Planting may be carried out directly
by the developer/ landowner, or the developer/landowner may pay into a dedicated
municipal tree planting fund (or sometimes a more general fund which supports
tree planting) in lieu of planting required trees. The term "tree bank"
may be used to describe the actual planting site, as in the following example:
Tree Bank: A site such as a school or public park, where the owner/developer shall donate and plant the required trees when it is not feasible to plant the required trees within their site’s project area. [Fulton Co., GA: Tree Preservation Ordinance Sec. I.III.33]
Alternatively, in some communities, the fund used for in-lieu fees is referred to as the "tree bank".
2. Establishing tree/forest preserves on public or private land through transfer of title to a public agency, the use of conservation easements or deed restrictions, or other methods. In contrast to the first tactic, trees or forested areas to be "banked" or preserved are already in place. As above, establishment of the preserve may occur directly (for example, through the dedication of a portion of a parcel to be developed as public parkland or open space) or through the use of in-lieu fees. The above tactics are not mutually exclusive and a tree ordinance may allow for planting, protection, direct mitigation, and in-lieu fees.
The term "tree bank" has also been used to describe other horticulture- or forestry-related concepts or programs. These include:
Temporary storage of trees removed from a site being developed. Trees (typically small diameter) are removed with a tree spade or in some other fashion, stored (i.e., "banked") temporarily, and subsequently replanted either at the same site or elsewhere. This technique could be used to help conserve locally-adapted native trees or locally rare trees, but may not be particularly cost effective for many situations.
In-ground tree nursery used as a source of larger planting stock. Trees seeds, seedlings, or small saplings are planted in either temporary (e.g. vacant lots) or permanent nursery areas for later transplantation. Such nurseries may be used as a source of low-cost planting materials for community groups or residents. This approach could also be used provide a source of locally native trees that would not otherwise be available from commercial sources.
Plantings of trees in protected areas for the purpose of maintaining genetic reserves. An organization known as the Forest Ecosystem Rescue Network has used the Tree Bank term to describe a program intended to create genetic reserves of tree species in locations outside their natural ranges.
Database of sources of free trees available to conservation groups. A program known as the Tree Bank Register (Great Britain) maintains a database of sources of tree planting stock that are available for free distribution to private citizen groups such as conservation organizations.
Although "tree bank" has a nice ring to it, it has been applied to
a wide variety of programs (and in some cases to organizations). It is certainly
legitimate to define the term in a tree ordinance and use it locally in that
sense. However, the fact that different jurisdictions use the term in different
ways may lead to confusion. In general, we recommend the use of more descriptive
(albeit more prosaic) terms such as "tree planting fund" or "off-site
mitigation planting" to describe the off-site mitigation tactics that are
specified in the ordinance.