Chapter 1.2
Low-Impact Development and Stormwater Management

• ALL
• Remove Code Barriers
• Create Incentives
• Fill Regulatory Gaps

Native Trees and Removal of Invasive Trees

INTRODUCTION

Tree mitigation ordinances seek to grow the local tree canopy by requiring the replacement of removed trees or, if that is not possible, taking alternative actions aimed at restoring green-space.[1] (see Expand Tree Canopy Cover). These ordinances go a step farther and require specific types of trees be used for mitigation and address the removal of smaller trees, bushes, grasses, native woodlands, and wildflowers.[2] Furthermore, ordinances can require the removal of invasive trees and their replacement with native trees.

Municipalities typically require developers or homeowners to apply for tree removal permits when seeking to remove certain types of protected trees. Protected trees can include native, heritage, and historic trees. Invasive trees are usually not considered protected, and thus may not require a permit to be removed. Further, depending on the jurisdiction, invasive trees may or may not need to be mitigated. Pursuant to this ordinance, upon approval, or as a condition of approval, protected trees removed during the course of development must be replaced from a list of approved trees. The list is frequently comprised of native trees, or at minimum, the species that have been proven to be suitable to the area. Additionally, municipalities have the option of requiring that a certain percentage of trees used as replacements be native to the area.[3] These ordinances may also identify invasive trees and require removal of those trees prior to approval.[4]

EFFECTS

Thousands of trees are destroyed every year. These trees provide critical services that are vital to many associated ecosystems and include purification of air and water, soil retention, and a variety of physical and psychological benefits. Requiring developers to replace trees removed during development with native trees, allows a community to continue to retain ecosystem benefits associated with trees. Such benefits can often be amplified with the use of native species. Trees are able to capture large amounts carbon dioxide, making them one of the most affordable and effective means of combating climate change.[5] Furthermore, they capture other pollutants, such as nitrous oxides and sulfur dioxides, which improves overall air quality.[6] Trees also aid in stormwater management and prevent further deterioration of water quality.[7] An urban tree with a 25-foot canopy with corresponding soil is capable of managing an inch of rainfall per 2,400 square feet of impervious surface through soil storage.[8] Interception and evapotranspiration also work to decrease runoff and the amount of stormwater entering municipal storm sewer systems.[9] Additionally, trees provide services in the areas of energy conservation and climate control.[10] They intercept sunlight before it is able to reach surfaces that trap heat and provide shade to buildings which cools the interior and exterior, thus reducing the amount of energy needed to artificially cool interior spaces.[11]

Requiring that replacement trees be native, or at minimum non-invasive, is especially important and can further benefit a community. Native trees are those that occur naturally in a region and are essential to protecting the biodiversity of that area.[12] Insects, birds, and other animals have co-evolved with native trees and without these native habits the associated food chain(s) is/are severed, stressing the survival of species that rely on these habits.[13] In addition, non-native trees often carry invasive pests that out compete the native species, destroying the existing habitat.[14] Because they are adapted to the soil, native trees can develop deeper and more complex root systems which help the trees hold more water, making them more efficient at stormwater management. Most native trees require less maintenance, making them less costly to maintain.[15]  Typically, native trees do not require the same level of watering as non-native species and do not require fertilizer and chemicals/pesticides.[16]

EXAMPLES

Ventura County, CA

Within the coastal zone of Ventura County developers are required to protect trees and/or mitigate tree loss in order to preserve their ecological value and visual quality.[17] Keeping in place all protected trees is the most preferred approach pursuant to this ordinance, followed by on-site mitigation, off-site mitigation, and, finally, in-lieu fees.[18] When removal of a protected tree cannot be avoided, on-site mitigation requires the developer to transplant or replace the tree on the same property.[19] The standards for the replacement tree vary according to the type of tree that was removed. If one protected native tree is removed it must be replaced with no less than ten native trees.[20] Heritage trees—non-native, non-invasive, trees with unique value that are considered irreplaceable due to their rarity, distinctive feature, or prominent location—are also required to be replaced, provided they meet certain criteria.[21] If the tree is located in a public area, or prominent location as seen from public viewing areas, the replacement must be the same species as the tree removed, of similar size, and planted in close proximity to where the removal took place.[22] Heritage trees that are not viewable from or located in public areas are required to be replaced with native trees.[23]

To view the provision, see Ventura County, CA- Code of Ordinances 8178-7.6 (2016).

Addison, TX

Addison, TX requires that the existing natural landscape, particularly native oak, elm, and pecan trees, be reasonably preserved.[24] The Town requires property owners to replace any dead, removed, missing, improperly pruned, or damaged trees, within thirty days of notification.[25] The list of suggested trees for replacement consist of trees native to Texas, as well as those that have been proven to be suitable to the area.[26] Trees that are not listed may be used as replacement trees subject to Addison Park Department approval.[27] Property owners may not remove or transplant a tree contained on the list without first getting a tree permit.[28] Considerations for granting removal of a listed tree include the impact removal may have on erosion, soil moisture, retention, flow of surface waters and drainage systems, and impact on the public health, safety, and welfare of the Town.[29]

To view the provision, see Addison, TX- Code of Ordinances § 34-208 (2016).

ADDITIONAL EXAMPLES

Union Springs, AL Code of Ordinances § 10.1 (2013) (replacement trees are required to be native or non-invasive exotics not likely to outcompete native species).

Stillwater, MN Code of Ordinances § 31-522 (Current through 2018) (replacement trees must be on the City approved list and more than 50% of the replacements must be native species).

Parkland, FL Code of Ordinances § 95-1010 (2015) (requiring a minimum of 30% native trees be used as replacement trees).

Evanston, IL Code of Ordinances § 7-8-8-7 (2012) (protected trees that are removed are required to be replaced with group A trees, the highest rated based on community value and genetic quality).