Mitigation Policy for Tree Removal in the United States: A Review of Terms, Replacement Ratios, and Jurisdictional Variation

1. Introduction

Urban trees provide a wide array of ecosystem services (Guo et al., 2019; Nowak & Greenfield, 2018; Elmqvist et al., 2015; Roy et al., 2012; Escobedo et al., 2011; Nowak & Dwyer, 2007; McPherson et al., 1997). The delivery of ecosystem services is closely tied to the structure, composition, and continuity of urban tree canopy (McPherson et al., 2016). Restoring, protecting, and investing in green infrastructure, including tree canopy, may prove not only ecologically beneficial but also economically sound (Elmqvist et al., 2015). However, because trees can take decades to mature and deliver their maximum ecological benefits (Nowak et al., 2007; Dwyer et al., 2003), the loss of existing trees, particularly large, established specimens, represents a meaningful reduction in ecosystem service capacity that cannot be quickly recovered through new plantings alone (McPherson et al., 1997).

In the United States (US), urban tree canopy management is primarily handled at the local level, due to the absence of a national urban forest policy framework (Pedley et al., 2026; Hargrave et al., 2022; Koeser et al., 2021). Local governments have implemented a variety of regulatory strategies to protect their urban forests, which are classified as command-and-control mechanisms, that set requirements for protection and impose penalties for violations; or as incentive-based mechanisms, that promote voluntary conservation through positive reinforcement (Pedley et al., 2026; Holzman-Gazit & Kaplinsk, 2026; Kuzma et al., 2026; Stern, 2023; Ordonez-Barona et al., 2021; Hahn & Stavins, 1991; Profus & Loeb, 1990). Tree mitigation policies vary between command-and-control and incentive mechanisms, as they seek to preserve trees by mandating that anyone intending to remove a regulated or protected tree, usually known as trees distinguished due to their heritage, biological features, or cultural importance (Ritchie et al., 2021), should compensate the broader community for that loss via replacement planting, contributions to a tree fund, or other approved measures (Clark et al., 2020; Lavy & Hagelman, 2019). Mitigation requirements are among the oldest and most widely adopted tools in urban forestry regulation (Profus & Loeb, 1990; Coughlin et al., 1988). They operate on the premise that tree removal imposes a public cost that must be offset, thereby transferring the cost of replacement associated with canopy loss to the private property owner who plans to remove an established tree (Norton et al., 2024).

In considering tree mitigation requirements, many communities acknowledge that mortality rates are generally higher for newly planted trees than for those that have reached establishment or medium size (Hilbert et al., 2019b; Roman et al., 2016; Roman et al., 2014a; Roman & Scatena, 2011). Both anthropogenic and biophysical factors can exacerbate vulnerabilities, increasing the likelihood of post-planting failure in urban environments (Hilbert et al., 2019a). From a policy perspective, these findings underscore the importance of prioritizing the preservation of existing mature trees as a primary strategy for sustaining ecosystem services, followed by effective management to minimize any adverse impact on the urban tree canopy, as Holzman-Gazit and Kaplinsk (2026) recommend by using the Mitigation Hierarchy Framework. According to this approach, after these two initial priorities (preserve and minimize), where tree removal is unavoidable, mitigation should be designed to restore ecological function by approximating pre-disturbance conditions as closely as possible, and lastly to offset ecological damages. However, the design and extent of these requirements vary across jurisdictions (Clark et al., 2020; Lavy & Hagelman, 2019) and do not always account for the ecosystem services provided (Nowak & Aevermann, 2019). While some ordinances mandate a simple one-for-one replacement of any removed tree, others require several replacement trees for every tree removed. They may also differ in imposing size minimums on replacement nursery stock, restricting replacement to native or same-species plantings, or requiring monitoring for multiple years post-planting (ISA, 2018). This variability reflects contrasts in local ecological conditions, policy traditions, available resources, and the political environment surrounding property rights and tree regulation (Pedley et al., 2026; Holzman-Gazit & Kaplinsk, 2026; Kuzma et al., 2026; Willis et al., 2024; Koeser et al., 2021; Clark et al., 2020; Lavy & Hagelman, 2019).

Despite their widespread use, tree mitigation policies have received limited systematic attention in the academic literature. While existing reviews of urban tree ordinances have documented the presence or absence of mitigation requirements (Holzman-Gazit & Kaplinsk, 2026; Clark et al., 2020; Lavy & Hagelman, 2019; ISA, 2018), our goal is to contribute to this literature by examining the specific content, structure, and terminology of mitigation provisions in depth. Understanding the key components of effective codes and policies, particularly provisions that are measurable and enforceable, may be essential to improving their implementation and effectiveness. This focus is warranted for numerous reasons. First, the ecological effectiveness of a mitigation policy depends not only on whether replacement is mandated, but on how much replacement is required, of what size and species, and under what conditions it must be planted and maintained (Holzman-Gazit & Kaplinsk, 2026; Lavy & Hagelman, 2019; Roman et al., 2015; Koeser et al., 2013). Second, the terminology used by local governments to communicate mitigation requirements to developers and property owners affects comprehension, compliance, and, ultimately, canopy outcomes (Pearsall et al., 2024). Third, understanding the landscape of existing mitigation policy design is necessary to compare and evaluate whether current practices are sufficient to achieve net zero canopy loss or net canopy gain, which has been identified as a critical goal for many urban forest management policies (Morgenroth et al., 2025; Nowak & Aevermann, 2019; Nowak & Greenfield, 2018). Fourth, sharing current examples in place may assist government authorities and other stakeholders in finding pertinent ideas to adapt and potentially implement in their communities (Kuzma et al., 2026).

The specific objectives of this study are to: (1) document the types and structures of tree mitigation policies currently in effect across some governments in the US; (2) analyze the replacement ratios, size standards, species requirements, and other procedural provisions encoded in these policies; (3) identify patterns and gaps in current mitigation policy design; and (4) discuss implications for more ecologically grounded and operationally clear mitigation frameworks.

2. Methods

2.1. Sample and Data Collection

This study draws on data collected as part of a broader national review of urban forest policies across US counties and incorporated places with populations over 50,000 (n=1,839), following the sampling framework described in Kuzma et al. (2026) and consistent with the approach established by Hauer and Peterson (2017). The present analysis focuses on jurisdictions in which a mitigation measure for the removal of regulated or protected trees on private property was identified and produced a ratio greater than 1:1 (one tree planted for each tree removed).

Data were collected between September 2024 and May 2025 through a systematic review of local codes and ordinances on third-party legal hosting platforms (Municode, American Legal Publishing, General Code Library, enCodePlus) and official government websites. The search procedure followed a structured two-phase approach: Phase One used the Policy Commons database to identify relevant documents, and Phase Two involved manual review of jurisdictions not captured in Phase One. A detailed description of the full data collection methodology is provided in Kuzma et al. (2026).

For this study, a tree mitigation provision is defined as any regulatory requirement specifying that urban trees removed from private property, whether through redevelopment, construction, or other permitted or non-permitted activities affecting urban trees, must be compensated for in a higher ratio than one tree planted for one tree removed or through an alternative compliance. We searched for replacement planting ratios, fee-in-lieu payment, or a combination of these measures, and included other conditions required for the replacement tree, such as size, species, location, timeline, and monitoring, along with any additional requirements. Provisions that merely stated that tree removal requires a permit and/or a replacement without specifying the number or conditions for fulfilling the obligation were also excluded.

2.2. Data Coding and Analysis

For each jurisdiction in the sample, the text of the relevant mitigation provision (recorded in the “Description” column of the dataset (Appendix A) was reviewed and coded for the following features: (1) general geographic analysis; (2) the replacement ratio or formula used; (3) whether a size standard (e.g., diameter at breast height (DBH), caliper, container size), a species requirement (e.g., same species, native species, approved species list), an on-site replacement preference was stated, or an off-site replacement was permitted; (4) whether a fee-in-lieu option was available; (5) whether a replanting timeline, or post-planting monitoring or survival guarantee was required; (6) other alternatives.

We used an inductive thematic analysis approach (Braun & Clarke, 2022; Bhattacherjee, 2012) to identify patterns and categories emerging from the policy language itself. Given the diversity and complexity of the ordinance language reviewed, entries were classified based on the most prominent mitigation mechanism described, drawing on categorizations identified in comparable codes and policies. This approach acknowledges that many provisions incorporate multiple conditions and alternative compliance pathways, and that terminology varies across jurisdictions even when underlying strategies are conceptually similar. For example, terms such as fees, fee-in-lieu, and fines are often used interchangeably; however, some jurisdictions distinguish among them, often using fees to refer to permit application costs, fines to denote penalties for unauthorized tree removal, and fee-in-lieu as monetary contributions to support replacement planting through designated tree funds. For this study, we will discuss fee-in-lieu as a compensatory strategy.

3. Results

3.1. Geographic Distribution

Of the 1839 locations, we found 162 mitigation entries in our sample, distributed across 36 US states, representing broad but uneven geographic coverage. California accounts for the largest share of entries (n=44, 27.2%), followed by Florida (n=24, 14.8%), Minnesota (n=11, 6.8%), and Illinois (n=10, 6.2%). Most mitigation regulations are set at the city/municipal level (68%) rather than at the county level (32%).

3.2. Replacement Ratio or Formulas Used

The analysis of tree mitigation requirements across the dataset reveals a diversity of approaches that governments use to determine replacement obligations for the removal of one tree. Each method reflects different priorities in balancing ecological function, practicality, and ease of implementation. The removal could have been authorized previously or not, and the replacement may also consider the species and size of the tree removed. The method for calculating the replacement generally falls into five main categories: DBH or trunk caliper, number of trees, canopy area, size-tiered systems, and other combined approaches or formulas (Table 1).

The simplest method is replacement based on the number of trees removed, where a fixed ratio (e.g., one-to-one or greater) is applied regardless of the size of the removed tree. This approach does not account for differences in ecological value between small and mature trees, or between species. The number of trees tends to appear in ordinances that define “significant”, “heritage”, or “protected” trees by a minimum size threshold or from specific species. Those trees represent a biological and cultural asset, designated for preservation due to their exceptional age, size, historical associations, or ecological contribution (Ritchie et al., 2021). As noted, we only included locations in our dataset when the ratio for replacement was higher than 1:1. The number of trees method is followed by another common approach, which relies on tree size metrics, such as DBH and trunk caliper. These provisions most commonly calculate replacement requirements based on the tree size, calculated by the DBH of the removed tree and expressed either as an inch-for-inch replacement or as a ratio of caliper inches of replacement stock to DBH removed. Notably, US Customary Units are generally used in the local tree policies, rather than metric, given measurement standards and traditions in the US.

An alternative mitigation framework identified defines compliance not through per-tree replacement ratios or cross-section measurements, but through the attainment or maintenance of a minimum canopy coverage threshold at site maturity. Under this approach, replacement requirements are based on canopy area equivalence, typically estimated using projected crown spread (drip line) derived from aerial imagery or standardized canopy metrics assigned to individual trees. This method often links mitigation to ecosystem service provision, such as shading and microclimate regulation, rather than tree count or stem size. Size-tiered compensation systems structure replacement requirements according to the size or class of the removed tree. Under this framework, trees are grouped into categories – typically based on DBH, trunk caliper, tree canopy area, or species of interest – and each category is assigned a corresponding replacement ratio, with larger trees requiring proportionally greater compensation. For example, a small tree may require a one-to-one replacement, whereas medium and large trees may require multiple replacements for each tree removed, or even a higher aggregate caliper planting or a bigger expected tree canopy area to replace. This approach relies on measured size thresholds and standardized tables.

Finally, some jurisdictions use combined methods or formulas, integrating those same metrics such as DBH, tree count, species, and canopy size factors. These jurisdictions have developed more comprehensive formal tier classification or matrix systems that structure the entire mitigation framework around a multi-level tree typology.

3.3. Whether a Size Standard, Species Selection, an On-Site Replacement Preference Was Stated, or an Off-Site Replacement Was Permitted for Replacement Trees

Beyond the replacement ratio itself, mitigation policies frequently include additional conditions that shape where, what kind, and what size of replacement trees must be installed. Table 2 provides examples of the most common complementary provisions identified across our sample.

The analysis reveals that governments employ a range of specifications for the size of replacement trees, reflecting different priorities in establishment success, cost, and ecological function. Some jurisdictions require a minimum planting size, typically expressed as trunk caliper (commonly around 1.5 to 4 inches or 3.8 to 10.2 cm), to ensure that newly planted trees provide some immediate structural presence. In some cases, minimum height requirements are also included, particularly for ornamental or screening purposes. A smaller set of policies references maximum sizes by discouraging nursery stock that may experience transplant shock or reduced establishment success. Additionally, while some ordinances require replacement trees to be of a comparable or equivalent size to those removed, without specifying exact measurements, others embed size requirements within tiered systems or tables, linking replacement ratios to the size of the removed tree.

A subset of municipalities specifies replacement tree size by container volume (liter/ gallons) or box size. These specifications typically reference sizes such as 15-gallon, 25-gallon, or 45-gallon (56.8 l, 94.6 l, 170.3 l), or 24-inch, 36-inch, or 48-inch (61 cm, 91 cm, or 122 cm) box size for trees, reflecting common industry practices for tree production and installation in the US. Additionally, gallon and box size requirements can be used in combination with other metrics, for example, specifies that a 15-gallon (56.8 l) tree replaces one inch (2.54 cm) DBH, a 24-inch (61 cm) box tree replaces two inches (5.08 cm), and a 36-inch (91 cm) box tree replaces three inches (7.62 cm), thereby creating an equivalency schedule that allows applicants to mix replacement stock sizes while meeting the overall mitigation obligation.

The analysis also shows municipalities including species selection requirements as part of their tree mitigation policies. These requirements often mandate the use of native (n=23, 14.2%), or regionally adapted species in general (n=5, 3.1%), or specify that replacements must come from an approved species list (n=10, 6.2%), or restrict invasive or undesirable species (n=18, 11.1%). In some cases (n=14, 8.6%), ordinances require species diversity, limiting the proportion of any single species to a percentage of the total replacement trees, encouraging biodiversity.

Another condition observed concerns the spatial placement of replacement trees. In most cases (n=41, 25.3%), replanting is required to occur on-site, typically in proximity to the location of the removed tree, to restore local canopy cover and associated ecosystem services. However, when site constraints – such as limited space, infrastructure conflicts, or unsuitable soil – preclude on-site replacement, ordinances often allow for off-site planting within the same jurisdiction or designated service area. In some instances (n=36, 22.2%), replacement trees may be allowed to be installed on public lands or given to municipal planting programs, subject to approval by the governing authority.

3.4. Whether a Fee-In-Lieu Option Was Available

When on-site or off-site planting is not feasible for the same reason previously appointed or due to demonstrated hardship by the property owner to replace the trees, many jurisdictions (n=58, 35.8%) provide the option of a fee in lieu of planting. Under this approach, the property owner pays a monetary contribution to a municipal fund and is relieved of replacing the tree. It can be structured as a last resort when replacement is not feasible or as an option for developers lacking sufficient planting space. Usually contemplates a contribution to the tree bank funds, to municipal urban forestry programs, or future public tree planting efforts.

Another observed mechanism similar to the fee-in-lieu is mitigation fees or fines, which are used as a penalty. Unlike fee-in-lieu payments, which generally function as a compensatory alternative mechanism when replanting is infeasible, mitigation fines are typically imposed on top of replanting, and in cases of unauthorized tree removal, such as when trees are removed prior to or without a permit approval or when there is a failure to replace removed trees, usually in violation of applicable regulations. In these situations, jurisdictions commonly require payment based on predetermined values assigned per tree or per inch of trunk diameter removed, sometimes incorporating the appraised value of the tree and additional penalty multipliers. The resulting funds are frequently directed toward the same outputs, such as municipal urban forestry initiatives, tree replacement programs, or broader canopy restoration efforts.

Fee-in-lieu as an offsetting technique is typically calculated using standardized formulas that reflect the characteristics of the trees removed, including DBH, canopy area, or the total number of trees. In some jurisdictions, compensation is based on an appraisal of the tree’s economic value, incorporating factors such as species, condition, and functional contributions. Common approaches include assigning a predetermined monetary value per inch of diameter (or caliper-inch), applying fixed rates per tree, or using multiplier factors to account for ecological significance. In other cases, fee structures are informed by estimates of the costs of buying plant material, planting, irrigating, and maintaining one new tree in that jurisdiction. Alternatively, some jurisdictions adopt a more flexible approach, leaving the final compensation amount subject to negotiation between the property owner and the governing authority (Table 3).

3.5. Whether a Replanting Timeline, a Post-Planting Monitoring, or a Survival Guarantee Was Required

Replanting timelines are typically defined relative to either the date of tree removal, notice of violation, or the issuance of a permit, and vary considerably across jurisdictions, ranging from as little as 30 days to up to 12 months, which can be extended for another 12 months. In some cases, the timeline reports to the issuance of a certificate of occupancy. Flexibility is often incorporated for construction projects, allowing replacement planting to be deferred until project completion rather than requiring immediate installation. Despite these provisions, the absence of clearly defined timelines in a substantial portion of the dataset is notable (n=113, 69.8%), potentially affecting the timely recovery of canopy cover.

The analysis also identified a small subset (n=27, 16.7%) of jurisdictions that include explicit post-planting monitoring requirements, potentially influencing property owners’ accountability and long-term mitigation success. Specifically, some of these jurisdictions incorporate language indicating that replacement trees must be installed, maintained, or successfully established within specific timeframes. This period functions not as a planting deadline but as a warranty for tree survival and establishment, meaning that if a newly planted tree fails within this period, it must be replaced by the property owner. Other cases include post-planting inspections or multi-year monitoring requirements. Ordinances define monitoring periods ranging from one to ten years, during which property owners are responsible for ensuring not only survival, but also the health of newly planted trees. These provisions often include additional obligations for irrigation, fertilization, initial pruning, and training.

Another strategy targeting replaced tree establishment according to industry standards is requesting performance bonds and financial guarantees (letters of credit, deposit in cash escrow accounts, and set-aside letters) from property owners who intend to remove a tree, and it will be used specifically to afford eventual tree maintenance and replacement (n=21, 13%). This concept can be confused with fee-in-lieu, as some locations use these terms with similar meanings. Whereas a fee-in-lieu usually covers the costs for tree replacement and mainly substitutes the duty for planting, performance bonds relate to further tree maintenance for establishment and survival during a specific timeframe. In jurisdictions where performance bonds are codified, applicants are expected to post a financial security, typically ranging from 100% to 400% of the total cost of the required replacement planting and maintenance, prior to permit issuance. Usually, municipalities hold the bond for a predetermined amount of time or up to the final arborist inspection, which may be required to confirm that replacement trees have survived and are in acceptable condition. If trees fail, the bond will be used to fund their replacement and maintenance. If the tree thrives, the money returns to the property owner.

Table 4. Examples of policy provisions that include a timeline for installing the replacement trees, post-planting monitoring, or survival warranties required.

Conditions	Examples
Timeline for installing replacement	“Replacement trees must be installed prior to one of the following unless a deferral of installation is approved in subsection (E)(1)(d) of this section: i. Prior to the building permit final inspection when the tree will be planted on a lot or parcel with a new building. ii. Prior to land division final plat approval. iii. Prior to a final planning inspection for lots, parcels or tracts approved as open space.” (Bend City, OR)
	“The property owner must replace trees within 30 days from receipt of a written notice of violation for unlawful tree removal. The Administrative Officer may grant a time extension for tree replacement if the thirty-day requirement would mean that trees would be planted outside the appropriate planting season (April-June and September-November).” (Nashua City, NH)
	“Any replacement trees shall be planted within 60 days from the day the permit is approved.” (Baldwin County, AL)
	“1. For Development Permits: Replacement trees shall be planted prior to receiving Final Acceptance of public infrastructure or a Certificate of Occupancy for the development. 2. For Tree Permits: Replacement trees shall be planted within 90 days of critical alteration. If replacement trees cannot be planted within 90 days of critical alteration, the Director of Planning may approve a delay in replacement of up to six months after the date of critical alteration, provided the following conditions are met: a. The applicant provides an affidavit that all replacement trees will be planted within six months. b. The Director of Planning may require a cash deposit or surety bond in the approximate amount of the cost to replace the trees.” (McKinney City, TX)
	“The replacement trees must be planted within nine months of the date of removal or, if the removal was made to facilitate on-site construction, within nine months of the issuance of a certificate of occupancy.” (Buffalo City, NY)
	“Be planted within 12 months of the date of removal of the original tree(s) or at an alternative date specified by the municipality;” (Plainfield City, NJ)
	“Such new tree planting and/or payment of fee-in-lieu shall be satisfied within one year of the date of approval of a tree removal permit, except as such conditions may be extended for one year, in accordance with these regulations.” (New Rochelle City, NY)
Post-planting monitoring	“All relocated or replaced trees shall be inspected by the Zoning Administrator one (1) year after their planting to insure they are surviving in a healthy condition. Trees planted pursuant to this section that are found to be in declining condition shall be replaced by the owner of the parcel within thirty (30) days of notification from the Zoning Administrator. If replacement is necessary, there shall be a re-inspection six (6) months after the replacement planting.” (Charleston City, SC)
	“Restoration trees in accordance with this requirement shall be replaced if the tree(s) dies within two years after planting” (Hillsborough County, FL)
	“Significant trees and exceptional trees shall be maintained for the life of the project and for three (3) years following issuance of the certificate of occupancy. A three (3) year tree maintenance agreement shall be recorded on the Burien City Attorney-approved document.” (Burien City, WA)
	“A maintenance plan that includes maintenance measures for each retained, replaced and/or relocated tree for a minimum period of five (5) years. The owner shall record a maintenance covenant, pursuant to Chapter 16.84 or any other applicable law, approved as to form by the City, against the property to that subsequent property owners are bound by this condition. It is the property owner’s responsibility to request the removal of any such covenant from record once the maintenance period ends, and the City shall not unreasonably withhold consent for such removal. If during the required maintenance period the tree(s) is (are) declared unhealthy by a City approved certified arborist, the diseased trees shall be removed and replaced at the cost of the owner.” (Chino Hills City, CA)
	“All mitigation trees shall be monitored for a period of seven years. If at any time during that period mitigation trees are destroyed as a result of natural disaster, any destroyed mitigation trees must be replaced, and the mitigation period shall continue from the date of the original approval.” (Los Angeles County, CA)
	“Replacement Trees will continue to be identified as Replacement Trees for a period of ten (10) years after they are planted. […] The Mitigation Payment shall be assessed on a DBH basis, in accordance with the City of Cambridge’s most recent tree planting and maintenance contract inclusive of purchasing, planting, watering, and maintaining Replacement Trees for a period of not less than five years.” (Cambridge City, MA)
	“Any project subject to the requirements of this Division shall include a plan for long-term management and maintenance along with a specified funding mechanism. Long-term maintenance and management plans shall include annual inspections and provisions to replace trees or incorporate other protective measures (i.e., browse protection, perimeter fencing, irrigation repair, etc.) as necessary to meet the objectives of the adopted mitigation plan.” (Novato City, CA)
Survival warranties / Performance bonds	“A financial security shall be held by the City of Nashua for one year to ensure tree replacement in the event that tree replacement results in the death of any replacement trees. The security amount shall be assessed at three times the fair market value of the required replacement tree(s).” (Nashua City, NH)
	“The replacement trees shall be guaranteed for one year. The applicant shall file a cash bond with the city community development department in an amount to be determined by the staff to assure performance of this guarantee.” (Fontana City, CA)
	“Payment in Lieu of Maintenance. Requiring payment to the City of Monterey equivalent to the cost of two years’ maintenance by City of the removed tree(s), said payment to be used to fund the maintenance of additional trees planted off site.” (Monterey City, CA)
	“The Director shall ensure that security is posted in an amount sufficient to secure the maintenance and protection of any replacement tree not planted on public property for a period of three years. Said security shall be returned at the end of the three-year period if, in the Director’s judgment, the replacement trees are healthy and free of any defects. Any replacement tree that is not healthy or free of defects at the end of the three-year period shall be replaced, and security shall be held for another three-year period or until, in the Director’s judgment, the tree has been well established.” (Napa City, CA)
	“Tree Establishment Bond in the amount of five hundred dollars ($500) per tree in the mitigation package. If trees are to be planted offsite, installation of the trees will be the developer’s responsibility, and maintenance for a three-year term, from the date that the trees are planted will also be the developer’s responsibility. A Maintenance Agreement outlining proper care of trees to be planted offsite will also be required for a term of three years, unless waived by the Augusta Tree Commission.” (Augusta-Richmond County, GA)
	“Replanting security shall be required for any tree mitigation plan excluding payment of an in-lieu fee. The purpose of such security shall be to guarantee the applicant’s compliance with conditions of approval and City provisions regarding tree protection and preservation. Security may also be required at the discretion of the approving body to insure the completion of any additional work specified as a condition of permit approval or other approvals. B. The security shall be in the amount of one hundred (100%) percent of the estimated cost of the required work. The applicant shall include the cost estimate as part of the tree mitigation plan for City Arborist review and approval. The terms and conditions of the security shall be reviewed and approved by the Community Development Director prior to approval of the tree mitigation plan. C. The security may be in the form of a letter of credit, cash deposit, a combination thereof, or other acceptance method of security by the City and shall be approved by the City Attorney. D. Security posted on actual work required shall be maintained for a minimum of five (5) years. The City may require additional length of security of up to ten (10) years when larger trees are being planted and/or site conditions warrant. E. Any interest gained on security posted by requirement of the City shall accrue to the applicant or his or her designee.” (Elk Grove City, CA)

Table 4. Examples of policy provisions that include a timeline for installing the replacement trees, post-planting monitoring, or survival warranties required.

Conditions	Examples
Timeline for installing replacement	“Replacement trees must be installed prior to one of the following unless a deferral of installation is approved in subsection (E)(1)(d) of this section: i. Prior to the building permit final inspection when the tree will be planted on a lot or parcel with a new building. ii. Prior to land division final plat approval. iii. Prior to a final planning inspection for lots, parcels or tracts approved as open space.” (Bend City, OR)
	“The property owner must replace trees within 30 days from receipt of a written notice of violation for unlawful tree removal. The Administrative Officer may grant a time extension for tree replacement if the thirty-day requirement would mean that trees would be planted outside the appropriate planting season (April-June and September-November).” (Nashua City, NH)
	“Any replacement trees shall be planted within 60 days from the day the permit is approved.” (Baldwin County, AL)
	“1. For Development Permits: Replacement trees shall be planted prior to receiving Final Acceptance of public infrastructure or a Certificate of Occupancy for the development. 2. For Tree Permits: Replacement trees shall be planted within 90 days of critical alteration. If replacement trees cannot be planted within 90 days of critical alteration, the Director of Planning may approve a delay in replacement of up to six months after the date of critical alteration, provided the following conditions are met: a. The applicant provides an affidavit that all replacement trees will be planted within six months. b. The Director of Planning may require a cash deposit or surety bond in the approximate amount of the cost to replace the trees.” (McKinney City, TX)
	“The replacement trees must be planted within nine months of the date of removal or, if the removal was made to facilitate on-site construction, within nine months of the issuance of a certificate of occupancy.” (Buffalo City, NY)
	“Be planted within 12 months of the date of removal of the original tree(s) or at an alternative date specified by the municipality;” (Plainfield City, NJ)
	“Such new tree planting and/or payment of fee-in-lieu shall be satisfied within one year of the date of approval of a tree removal permit, except as such conditions may be extended for one year, in accordance with these regulations.” (New Rochelle City, NY)
Post-planting monitoring	“All relocated or replaced trees shall be inspected by the Zoning Administrator one (1) year after their planting to insure they are surviving in a healthy condition. Trees planted pursuant to this section that are found to be in declining condition shall be replaced by the owner of the parcel within thirty (30) days of notification from the Zoning Administrator. If replacement is necessary, there shall be a re-inspection six (6) months after the replacement planting.” (Charleston City, SC)
	“Restoration trees in accordance with this requirement shall be replaced if the tree(s) dies within two years after planting” (Hillsborough County, FL)
	“Significant trees and exceptional trees shall be maintained for the life of the project and for three (3) years following issuance of the certificate of occupancy. A three (3) year tree maintenance agreement shall be recorded on the Burien City Attorney-approved document.” (Burien City, WA)
	“A maintenance plan that includes maintenance measures for each retained, replaced and/or relocated tree for a minimum period of five (5) years. The owner shall record a maintenance covenant, pursuant to Chapter 16.84 or any other applicable law, approved as to form by the City, against the property to that subsequent property owners are bound by this condition. It is the property owner’s responsibility to request the removal of any such covenant from record once the maintenance period ends, and the City shall not unreasonably withhold consent for such removal. If during the required maintenance period the tree(s) is (are) declared unhealthy by a City approved certified arborist, the diseased trees shall be removed and replaced at the cost of the owner.” (Chino Hills City, CA)
	“All mitigation trees shall be monitored for a period of seven years. If at any time during that period mitigation trees are destroyed as a result of natural disaster, any destroyed mitigation trees must be replaced, and the mitigation period shall continue from the date of the original approval.” (Los Angeles County, CA)
	“Replacement Trees will continue to be identified as Replacement Trees for a period of ten (10) years after they are planted. […] The Mitigation Payment shall be assessed on a DBH basis, in accordance with the City of Cambridge’s most recent tree planting and maintenance contract inclusive of purchasing, planting, watering, and maintaining Replacement Trees for a period of not less than five years.” (Cambridge City, MA)
	“Any project subject to the requirements of this Division shall include a plan for long-term management and maintenance along with a specified funding mechanism. Long-term maintenance and management plans shall include annual inspections and provisions to replace trees or incorporate other protective measures (i.e., browse protection, perimeter fencing, irrigation repair, etc.) as necessary to meet the objectives of the adopted mitigation plan.” (Novato City, CA)
Survival warranties / Performance bonds	“A financial security shall be held by the City of Nashua for one year to ensure tree replacement in the event that tree replacement results in the death of any replacement trees. The security amount shall be assessed at three times the fair market value of the required replacement tree(s).” (Nashua City, NH)
	“The replacement trees shall be guaranteed for one year. The applicant shall file a cash bond with the city community development department in an amount to be determined by the staff to assure performance of this guarantee.” (Fontana City, CA)
	“Payment in Lieu of Maintenance. Requiring payment to the City of Monterey equivalent to the cost of two years’ maintenance by City of the removed tree(s), said payment to be used to fund the maintenance of additional trees planted off site.” (Monterey City, CA)
	“The Director shall ensure that security is posted in an amount sufficient to secure the maintenance and protection of any replacement tree not planted on public property for a period of three years. Said security shall be returned at the end of the three-year period if, in the Director’s judgment, the replacement trees are healthy and free of any defects. Any replacement tree that is not healthy or free of defects at the end of the three-year period shall be replaced, and security shall be held for another three-year period or until, in the Director’s judgment, the tree has been well established.” (Napa City, CA)
	“Tree Establishment Bond in the amount of five hundred dollars ($500) per tree in the mitigation package. If trees are to be planted offsite, installation of the trees will be the developer’s responsibility, and maintenance for a three-year term, from the date that the trees are planted will also be the developer’s responsibility. A Maintenance Agreement outlining proper care of trees to be planted offsite will also be required for a term of three years, unless waived by the Augusta Tree Commission.” (Augusta-Richmond County, GA)
	“Replanting security shall be required for any tree mitigation plan excluding payment of an in-lieu fee. The purpose of such security shall be to guarantee the applicant’s compliance with conditions of approval and City provisions regarding tree protection and preservation. Security may also be required at the discretion of the approving body to insure the completion of any additional work specified as a condition of permit approval or other approvals. B. The security shall be in the amount of one hundred (100%) percent of the estimated cost of the required work. The applicant shall include the cost estimate as part of the tree mitigation plan for City Arborist review and approval. The terms and conditions of the security shall be reviewed and approved by the Community Development Director prior to approval of the tree mitigation plan. C. The security may be in the form of a letter of credit, cash deposit, a combination thereof, or other acceptance method of security by the City and shall be approved by the City Attorney. D. Security posted on actual work required shall be maintained for a minimum of five (5) years. The City may require additional length of security of up to ten (10) years when larger trees are being planted and/or site conditions warrant. E. Any interest gained on security posted by requirement of the City shall accrue to the applicant or his or her designee.” (Elk Grove City, CA)

4. Discussion

4.1. The Diversity of Mitigation Approaches Reflects a Lack of Standardization

This review follows previous literature showing a myriad of approaches to tree mitigation. Even among the simplest metric – the replacement ratio – we identified at least five distinct categories of policy design, ranging from fixed ratios (tree number, DBH or trunk caliper, or tree canopy area) to complex, size-tiered calculations based on the size of the tree removed or formulas combining the metrics (e.g., number of trees for inches in DBH, or tree canopy area for number of trees). Additional conditions, such as what kind and what size of trees should be planted, where and when the replacement should happen, and if there is a fee-in-lieu option or which warranties should be considered for maintenance, include even more detailed specificities in a comparative analysis. This variability mirrors what was observed in previous literature (Pedley et al., 2026; Holzman-Gazit & Kaplinsk, 2026; Kuzma et al., 2026; Ordonez-Barona et al., 2021), and reinforces the broader finding in the urban forestry research that local tree governance in the United States is fragmented, context-specific, and largely unstandardized at the national level (Pedley et al., 2026; Holzman-Gazit & Kaplinsk, 2026; Morgenroth et al., 2025; Hargrave et al., 2022).

While context-sensitivity has real value, the current level of variability raises questions about whether mitigation policies with so many different aspects to consider may be achieving their stated objectives. For instance, a replacement ratio based on a simple fixed standard may prove inadequate to replace existing canopy cover over time, given the mortality risks facing newly planted urban trees (Hilbert et al., 2019a; Roman et al., 2014a; Roman et al., 2014b; Koeser et al., 2014; Roman & Scatena, 2011; Nowak et al., 2004). Even with full survival, it may take decades for young trees to grow to maturity and approximate the ecosystem services delivered by the mature specimens they replace (Nowak & Aevermann, 2019; Nowak & Dwyer, 2007; McPherson et al., 1997). The dominance of simple ratio – number of trees, diameter, or tree canopy area – requirements in our sample, associated with a lack of survival or monitoring provisions, suggests that many mitigation policies may function as administrative formalities rather than effective conservation mechanisms.

DBH or canopy size-based mitigation formulas are more promising, as these systems link replacement requirements to the actual size and canopy value of the removed tree (Nowak & Aevermann, 2019). However, DBH-based systems also introduce complexity that may be difficult for property owners and municipalities to administer consistently (Pearsall et al., 2024). The variability in how DBH equivalency is calculated, whether 1-inch (2.54 cm) DBH equals a 15-gallon (56.8 l), 24-inch (61 cm), or a 36-inch (91 cm) box, for instance, creates an uneven playing field in which a developer subject to one jurisdiction’s formula may face a very different replacement burden than one in a neighboring municipality, despite removing trees of identical size and value. This factor might interfere with public understanding of and compliance with tree canopy protection in the long run.

4.2. Fee-in-Lieu Mechanisms: Flexibility or Loophole?

Fee-in-lieu options appear to represent an important, underexamined dimension of mitigation policy design. These mechanisms acknowledge the practical reality that on-site replacement is not always feasible, and they redirect financial resources toward tree planting elsewhere in the community. In theory, a well-managed tree bank can pool mitigation funds to achieve strategic planting in high-priority locations, including areas identified for canopy equity improvement or ecological restoration, along with investments in mature tree maintenance.

In practice, however, the effectiveness of fee-in-lieu mechanisms relies to a great extent on the adequacy of the fee schedule, the governance and transparency of tree bank funds, and the rigor with which replacement plantings are implemented and maintained. Conceptually, fee-in-lieu mechanisms for tree mitigation can be compared to remedies in tort law, whereby environmental harm caused by one party is compensated through monetary payments intended to support restoration, approximate pre-disturbance conditions as closely as possible, and discourage future harmful conduct. Within this framework, mitigation fees might be calibrated to reflect the ecological value of the tree canopy loss and to incentivize preservation whenever feasible. If the monetary value imposed is too low or merely nominal, it may fail to discourage unnecessary tree removal and instead become absorbed as a routine cost of development rather than functioning as a meaningful compensatory or deterrent mechanism. Additional concerns may arise when mitigation payments are deposited into general municipal funds or loosely defined “tree fund accounts” without clear requirements regarding how, where, or when the funds might be expended. The absence of transparent accounting, performance tracking, or canopy-based restoration targets could be studied in the future to verify whether fee-in-lieu programs foster developers to satisfy mitigation obligations along with producing equivalent canopy recovery or ecosystem service replacement within the affected community. These concerns are consistent with broader critiques of mitigation banking and compensatory environmental policy instruments in the environmental economics literature (Hahn & Stavins, 1991). Willis et al. (2024), in a Florida study with developers, pointed out that while tree funds pile up, there is neither workforce available nor space suitable for replanting trees in a timely manner. Furthermore, from the property owners’ perspective, it may be difficult to understand that governments can maintain dedicated tree funds available for planting programs while being unable to use those same resources to assist with the preservation or maintenance of existing mature trees.

There is also a need for further research on the use of local tree mitigation funds. For instance, allowing mitigation funds to support the maintenance and preservation of existing trees, maybe even the ones on private properties, rather than being limited exclusively to new plantings, may represent an effective strategy for sustaining mature canopy cover and the ecosystem services already being provided (Riedman et al., 2022). Alternatively, providing funding for sidewalk or street repairs, when caused by private mature trees, which are under the responsibility of property owners, could represent another innovative approach (McPherson, 2000). Such infrastructure damage can pose a substantial financial burden on residents, leading to reluctance to plant new trees (Pearsall et al. 2024). Because established trees contribute disproportionately to functions such as shading, carbon storage, stormwater interception, and urban cooling, investing in their long-term health and survival may, in some cases, yield greater ecological benefits than relying solely on replacement planting programs. Moreover, managers may consider planting fewer trees while ensuring that adequate conditions are provided for their establishment and long-term survival (Eisenman et al., 2025; Roman et al., 2014a). Furthermore, the introduction of a SMART framework (specific, measurable, achievable, resourced, and time-bound) for mitigation policy design, as proposed for urban tree canopy governance by Morgenroth et al. (2025), could strengthen the accountability and effectiveness of fee-in-lieu mechanisms. Under such an approach, tree fund expenditures could be tied to documented canopy outcomes, publicly reported on a regular basis, and potentially be linked to measurable canopy coverage targets, thereby improving transparency and commitment by ensuring that mitigation payments translate into verifiable ecological gains.

4.3. Mitigation and the Tree Life Cycle

One consequential gap identified in this review concerns the treatment of timelines within mitigation ordinances. First, most jurisdictions do not establish a clear timeframe within which replacement trees must be installed. Second, many ordinances do not require long-term monitoring, maintenance periods, or follow-up inspections for replacement plantings, effectively releasing property owners from future responsibility once planting has occurred or a certificate of occupancy has been issued. Both timelines are critical for ensuring that the ecological functions lost through tree removal are restored as quickly and effectively as possible. Installation deadlines are necessary to ensure compliance with permit conditions and to minimize delays in canopy recovery, whereas monitoring requirements help ensure that replacement trees are properly maintained during the establishment period, thereby increasing the likelihood of long-term survival. The limited presence of monitoring requirements is particularly consequential given documented urban tree mortality rates (Morgenroth et al., 2025). Research indicates that newly planted urban trees experience substantially higher mortality than established trees, especially within the first one to three years following transplanting (Hilbert et al., 2019a; Roman et al., 2014a; Roman et al., 2014b; Koeser et al., 2013; Roman et al., 2011; Nowak et al., 2004). Without survival guarantees or longitudinal data for monitoring provisions (Roman et al., 2016), jurisdictions cannot confidently assume that mitigation plantings will contribute to long-term canopy recovery, potentially allowing substantial ecosystem service losses to remain effectively unmitigated despite formal compliance with replacement requirements.

This finding resonates with the holistic life cycle framing proposed in Kuzma et al. (2026), which suggested that urban forest management – whether implemented through incentives or regulations – should address all stages of a tree’s life cycle, including planting and early care, ongoing maintenance, technical assistance, removal and replacement, and preservation of mature canopy. Residents are also keenly aware of management challenges across the tree life cycle (Pearsall et al. 2024). In contrast, some mitigation policies reviewed in this study focus predominantly on the removal and initial replacement stages, with comparatively limited attention given to the long-term maintenance and survival of replacement plantings. The distinction between the rigor applied to removal thresholds – which frequently include detailed size classifications, canopy assessments, and permitting procedures – and the comparatively limited requirements governing post-planting success reveals a systemic asymmetry in mitigation policy design. More robust mitigation frameworks, as observed in a smaller subset of jurisdictions, require applicants to guarantee tree survival over a meaningful establishment period (e.g., three to ten years), often supported by performance bonds, maintenance requirements, and documented outcomes through inspections or reporting protocols. If tree removal is subject to extensive regulatory oversight, equivalent attention could be directed toward ensuring that replacement trees successfully establish and contribute to long-term canopy recovery and ecosystem service restoration.

4.4. Species Requirements and Ecological Coherence

The inclusion of species-specific requirements and diversity considerations in some mitigation ordinances reflects a growing recognition that ecological coherence, and not merely quantitative canopy replacement, are relevant to urban tree mitigation policy. Requirements favoring native species or prescribed species palettes respond to the well-documented ecological importance of species diversity (Chambers-Ostler et al., 2024; Hilbert et al., 2023; Hauer & Peterson, 2017; Koeser et al., 2013), local adaptation (Roman et al., 2014b), historical and cultural landscape relevance (Roman et al., 2018), and functional redundancy within urban ecosystems (Elmqvist et al., 2015; Schwarz et al., 2015). Replacing a removed tree with the same species may help preserve genetic lineage, habitat value for associated wildlife, and ecosystem functions linked to species-specific traits. In contrast, policies that promote native species, establish approved species lists, or require species diversity in replacement plantings may facilitate nursery production planning by creating predictable demand for a broader and ecologically appropriate palette of planting material for urban landscapes.

However, species requirements also introduce challenges. Requiring the same species may be ecologically inappropriate in contexts where the removed tree was itself an invasive, disease-susceptible, or inappropriately sited specimen. Several jurisdictions in our sample acknowledge this tension by permitting species substitution with arborist approval, or by restricting replacement to approved species lists that exclude invasive taxa. This is an interesting design feature that balances ecological aspirations with practical flexibility.

Looking ahead, the appearance of invasive insect pests (e.g., emerald ash borer – Agrilus planipennis), diseases (e.g., Dutch elm disease, caused by fungal pathogen Ophiostoma novo-ulmi), and the projected impacts of climate change on regional tree species suitability (McPherson et al., 2016) will require mitigation policies to incorporate climate-adaptive species selection guidance. A mitigation policy that requires same-species replacement of ash trees (Fraxinus spp.) in regions where ash is being decimated by emerald ash borer, for example, is not ecologically sound (Hauer & Peterson, 2016). In other cases, selecting drought-tolerant species may represent a more appropriate replacement strategy, particularly when considering the practical capacity for post-planting stewardship and maintenance (Roman et al., 2014b). Along the same lines, including diversity recommendations (e.g., no more than 25% or 30% of replacements should be from the same species) may also prevent decimation in extreme ecological breakdowns (Hilbert et al., 2023; Hauer & Peterson, 2016; Koeser et al., 2013). Forward-looking mitigation frameworks could incorporate dynamic species guidance tied to current regional contexts.

4.5. Connecting Mitigation and Incentive Policies

The existence of tree ordinances was previously studied and is considered a factor influencing tree protection (Guo et al., 2019; Hilbert et al., 2019b; Sung, 2012; Landry & Pu, 2010). Mitigation policies are triggered by removal and serve primarily to offset canopy loss (Ordóñez-Barona, 2021; Coughlin et al., 1988). Incentive policies, by contrast, are proactive; they encourage tree planting and preservation before any removal occurs (Pedley et al., 2026; Holzman-Gazit & Kaplinsk, 2026; Kuzma et al., 2026; Willis et al., 2024; Koeser et al., 2023; Ordóñez-Barona, 2021).

Neither approach alone is sufficient to support holistic urban forest management (Pedley et al., 2026; Holzman-Gazit & Kaplinsk, 2026; Willis et al., 2024; Koeser et al., 2023; Ordóñez-Barona, 2021). Mitigation policies that lack adequate replacement ratios, survival guarantees, or species selection guidance may permit continued net canopy loss despite formal regulatory compliance. Conversely, incentive-based policies that target only the planting stage, without addressing long-term maintenance and the risks associated with tree aging and dying, leave substantial portions of the tree life cycle unsupported (Kuzma et al., 2026; Eisenman et al., 2025; Pearsall et al., 2024). A more comprehensive policy framework would integrate preventive incentives across all stages of the tree life cycle, with rigorous, ecologically grounded mitigation requirements for unavoidable removal, thereby potentially improving the long-term capacity to maintain and expand urban tree canopy. This integrated approach is consistent with the Mitigation Hierarchy referenced in recent urban forestry policy literature (Holzman-Gazit & Kaplinsk, 2026), which prioritizes the sequential steps of (1) avoiding adverse impacts, (2) minimizing unavoidable impacts, (3) rehabilitating affected areas, and, only as a final measure, (4) offsetting residual losses. The mitigation policies reviewed in this study predominantly address the final stages – compensatory replacement or offsetting – while providing comparatively limited mechanisms to encourage avoidance or minimization prior to removal. Embedding preservation incentives and impact-avoidance strategies within the same regulatory framework as mitigation requirements could encourage developers to redesign projects in ways that retain existing trees, rather than treating mitigation solely as a routine compliance obligation.

4.6. Emerging Mitigation Forms: Toward a More Comprehensive Toolkit

Some supplementary mitigation forms were identified: performance bonds, monitoring requirements, and accountability for survival, collectively suggest that current mitigation practice in some U.S. jurisdictions extends considerably beyond the tree ratio and tree replacement frameworks captured in our dataset. These mechanisms are not mere variations on the replacement planting theme; they represent fundamentally different logics of long-term commitment with tree canopy establishment, each with distinct assumptions, operational requirements, and governance implications.

Performance bonds are particularly important because they target the vulnerable post-planting phase, when newly installed trees are most vulnerable to stress, improper maintenance, drought, vandalism, or mortality. Under this mechanism, developers or property owners are typically required to deposit a financial guarantee that is only released after the replacement trees survive a specified monitoring period and pass inspection by the responsible governmental agency, thereby creating accountability for long-term outcomes. The combination of performance bonds with monitoring requirements, replacement obligations for dead trees, and tree health inspections may contribute to the intended canopy replacement goals of mitigation policies. By ensuring that financial responsibility remains in place until trees are successfully established, they reinforce the idea that effective urban forest mitigation should not be measured merely by the number of trees planted, but by the long-term survival and functionality of the resulting canopy.

Beyond ensuring long-term accountability, performance bonds, monitoring commitment, and survival warranty, may also indirectly function as an incentive for mature tree preservation. Because these mechanisms extend financial responsibility through monitoring and establishment periods, developers may perceive tree removal as a more costly and administratively demanding process. Guo et al. (2019) emphasized that property owners’ perceptions of high tree removal costs can influence decisions regarding whether to retain or remove trees on their land. Consequently, these strategies may encourage greater consideration of preservation-oriented alternatives during site planning, including more flexible and creative design adaptations aimed at retaining existing mature canopy elements. In this sense, such mechanisms may support a transition from reactive mitigation approaches toward more proactive strategies aligned with the higher levels of the mitigation hierarchy, particularly avoidance and preservation (Holzman-Gazit & Kaplinsk, 2026).

4.7. Implications for Policy Design

Based on the patterns identified in this review, we offer the following recommendations for local governments seeking to strengthen their tree mitigation frameworks. First, policymakers may consider calibrating replacement ratios to account for the value of the removed tree, the mortality risk of the replacement species and stock size, and the time required for replacement trees to approximate the ecosystem service capacity of the trees they replace. If the goal of tree protection ordinances is to maintain or enhance the existing urban forest canopy, a simple ratio replacement of a mature tree with a 15-gallon (56.8 l) sapling might not achieve meaningful compensation; ratios that increase with the size and condition of the removed tree might better reflect this reality.

Second, if the objective of mitigation-based policies is to increase tree canopy, maybe including a minimum establishment period during which replacement trees must be maintained and, if they fail, replaced. A two- to ten-year monitoring requirement with a performance bond or equivalent assurance mechanism could potentially improve the likelihood that mitigation plantings contribute to lasting canopy recovery, consistent with what has been recommended for tree planting programs generally (Roman et al., 2014b; Koeser et al., 2013).

Third, fee-in-lieu or mitigation fees mechanisms may benefit from transparent accounting, regular public reporting, and clear expenditure timelines tied to measurable canopy outcomes. Sharing this information with the community may possibly enhance tree stewardship. When feasible, the inclusion of a provision for using the funds to assist maintenance of mature trees on private properties within the community may potentially be a way to fund the creation of incentives for preserving the already established urban tree canopy.

Fourth, mitigation policy language might conceivably enhance communication when it is clear, accessible, and consistently applied across departments. We align with previous research (Kuzma et al., 2026; Dwyer et al., 2002) noting that urban forest regulations are sometimes scattered across multiple sections of local codes and administered by multiple departments (e.g., forestry, parks and recreation, sustainability, planning, permitting), perhaps creating confusion for applicants and enforcement challenges for officials. Highly elaborated tables may also disrupt regular understanding of how mitigation works. Consolidating mitigation requirements within a clearly labeled section of the tree ordinance, with a plain-language summary available to property owners, could potentially improve both compliance and public understanding.

Fifth, local governments may consider defining a replanting window, since mitigation obligations might be indefinitely deferred, particularly in multi-phase development projects or in cases where enforcement capacity is limited. This represents a meaningful gap in the operational effectiveness of many mitigation frameworks. Determining a clear deadline for completing the mitigation efforts may help to overcome this challenge.

5. Limitations and Future Research

Several limitations of this study should be acknowledged. First, the primary sample is limited to jurisdictions with populations over 50,000, excluding smaller municipalities and rural communities. The patterns identified here may not generalize to smaller jurisdictions, which in some regions represent the majority of local governance activity. This study focused on urban trees located on private property to the greatest extent possible. However, some codes and policies do not distinguish between mitigation frameworks for private-property trees and public trees located within easements. Because these contexts may involve different regulatory approaches to tree mitigation, further research is needed to better understand these distinctions. Additionally, mitigation ratios of one tree removed that are mitigated by replanting one tree were not included in our dataset, unless presenting other conditions deemed beyond business-as-usual, limiting the data collected. There is a need for comparative research across countries to reveal how different regulatory frameworks operate in diverse contexts, as well as studies to evaluate compliance with and constitutionality of the mitigation policies.

Finally, future research could examine the relationship between mitigation policy stringency and canopy cover outcomes at the jurisdictional level, building on prior work linking tree ordinance adoption to canopy preservation or gain (Hilbert et al., 2019b; Sung, 2012; Landry & Pu, 2010). Understanding whether higher replacement ratios, survival requirements, or performance bond provisions translate into measurable canopy benefits would provide critical empirical grounding for the policy recommendations offered here.

6. Conclusions

This review of tree mitigation policies across US states reveals a landscape of considerable diversity in how local governments require compensation for the removal of urban trees on private properties. Replacement ratios range from simple substitutions to complex, size-tiered DBH-based calculations, tree canopy area replacement, or a combination of metrics; fee-in-lieu mechanisms provide flexibility but require stronger accountability frameworks; and complementary provisions addressing species selection, replacement timing, post-planting monitoring, and performance bonds are present in only a few ordinances. Taken together, these patterns indicate that while many current mitigation policies are administratively functional, they may fall short of achieving the ecological objective of maintaining or restoring urban canopy, and that a more comprehensive, outcomes-oriented mitigation toolkit is both possible and increasingly available as a model.

This study underscores the need for an integrated approach to urban forest governance that combines robust mitigation requirements with proactive incentives for preservation, planting and early care, maintenance, technical assistance, and removal and replacement, which addresses all stages of the tree life cycle. As urban forests face increasing pressures from development, warmer and drier temperatures, invasive pests, and aging canopy structure, the design of effective mitigation policy, drawing on the full range of mechanisms documented here, could be determinant of whether cities can maintain, recover, or expand their tree canopy for future generations. We hope this review serves as a useful resource for urban forest managers, planners, policymakers, and researchers seeking to strengthen tree mitigation frameworks and as a foundation for continued empirical investigation into the prevalence, design, and outcomes of these policies in practice.