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Because of their diversity and use of vegetation, tree trench and tree box practices provide multiple green infrastructure benefits. | Because of their diversity and use of vegetation, tree trench and tree box practices provide multiple green infrastructure benefits. | ||
− | *[https://stormwater.pca.state.mn.us/index.php?title=Water_quality_benefits_of_Green_Stormwater_Infrastructure Water quality]: Tree trenches and tree boxes are an excellent stormwater treatment practice due to the variety of pollutant removal mechanisms including vegetative filtering, settling, evaporation, infiltration, transpiration, biological and microbiological uptake, and soil adsorption. Tree trenches and tree boxes can be designed as an effective infiltration / recharge practice, particularly when parent soils have high permeability (> ~ 0.5 inches per hour). Link to water quality information for tree trench/tree box - [https://stormwater.pca.state.mn.us/index.php?title=Calculating_credits_for_tree_trenches_and_tree_boxes] | + | *[https://stormwater.pca.state.mn.us/index.php?title=Water_quality_benefits_of_Green_Stormwater_Infrastructure '''Water quality''']: Tree trenches and tree boxes are an excellent stormwater treatment practice due to the variety of pollutant removal mechanisms including vegetative filtering, settling, evaporation, infiltration, transpiration, biological and microbiological uptake, and soil adsorption. Tree trenches and tree boxes can be designed as an effective infiltration / recharge practice, particularly when parent soils have high permeability (> ~ 0.5 inches per hour). Link to water quality information for tree trench/tree box - [https://stormwater.pca.state.mn.us/index.php?title=Calculating_credits_for_tree_trenches_and_tree_boxes] |
− | *[https://stormwater.pca.state.mn.us/index.php?title=Water_quantity_and_hydrology_benefits_of_Green_Stormwater_Infrastructure Water quantity/supply]: Tree trenches and tree boxes can be designed as an effective infiltration / recharge practice when parent soils have high permeability. Large tree trench systems can be incorporated into ultra-urban settings and provide significant volume control. For lower permeability soils an [https://stormwater.pca.state.mn.us/index.php?title=Glossary#U underdrain] is typically used and some infiltration and rate control can be achieved. | + | *[https://stormwater.pca.state.mn.us/index.php?title=Water_quantity_and_hydrology_benefits_of_Green_Stormwater_Infrastructure '''Water quantity/supply''']: Tree trenches and tree boxes can be designed as an effective infiltration / recharge practice when parent soils have high permeability. Large tree trench systems can be incorporated into ultra-urban settings and provide significant volume control. For lower permeability soils an [https://stormwater.pca.state.mn.us/index.php?title=Glossary#U underdrain] is typically used and some infiltration and rate control can be achieved. |
− | *Energy | + | *'''Energy savings''': Urban trees can reduce energy needs as a result of heat mitigation associated with reduction in impervious surface, cooling associated with evapotranspiration, and shading. McPherson and Simpson (2003) estimated existing trees are projected to reduce annual air conditioning energy use by 2.5% with a wholesale value of $ 485.8 million. Peak load reduction by existing trees saves utilities 10% valued at approximately $778.5 million annually, or $4.39/tree. Other researchers have documented reduced energy consumption associated with urban trees ([https://escholarship.org/content/qt4qs5f42s/qt4qs5f42s.pdf], [https://www.sciencedirect.com/science/article/pii/S037877880900005X], [https://trees-energy-conservation.extension.org/urban-trees-energy-conservation/]). |
− | *[https://stormwater.pca.state.mn.us/index.php?title=Climate_benefits_of_Green_Stormwater_Infrastructure Climate resiliency]: Properly installed and maintained trees provide significant benefits for climate resiliency. The primary benefit is through carbon sequestration. A mature tree typically sequesters about 50 pounds of carbon per year, depending on species, tree health, and tree growth rate ([https://www3.epa.gov/climatechange/Downloads/method-calculating-carbon-sequestration-trees-urban-and-suburban-settings.pdf U.S. Department of Energy, Energy Information Administration, 1998)]. [https://www.ncrs.fs.fed.us/pubs/jrnl/2002/ne_2002_nowak_002.pdf Nowak and Crane] (2002) estimated that urban forests store about 700 million tonnes of carbon. Although carbon storage per unit area was only about half that in forested areas, urban forests grow quickly and trees reach maturity sooner compared to natural forests. | + | *[https://stormwater.pca.state.mn.us/index.php?title=Climate_benefits_of_Green_Stormwater_Infrastructure '''Climate resiliency''']: Properly installed and maintained trees provide significant benefits for climate resiliency. The primary benefit is through carbon sequestration. A mature tree typically sequesters about 50 pounds of carbon per year, depending on species, tree health, and tree growth rate ([https://www3.epa.gov/climatechange/Downloads/method-calculating-carbon-sequestration-trees-urban-and-suburban-settings.pdf U.S. Department of Energy, Energy Information Administration, 1998)]. [https://www.ncrs.fs.fed.us/pubs/jrnl/2002/ne_2002_nowak_002.pdf Nowak and Crane] (2002) estimated that urban forests store about 700 million tonnes of carbon. Although carbon storage per unit area was only about half that in forested areas, urban forests grow quickly and trees reach maturity sooner compared to natural forests. |
− | *[https://stormwater.pca.state.mn.us/index.php?title=Air_quality_benefits_of_Green_Stormwater_Infrastructure Air quality] | + | *[https://stormwater.pca.state.mn.us/index.php?title=Air_quality_benefits_of_Green_Stormwater_Infrastructure '''Air quality'''] |
− | *[https://stormwater.pca.state.mn.us/index.php?title=Wildlife_habitat_and_biodiversity_benefits_of_Green_Stormwater_Infrastructure Habitat improvement]: Individual trees can provide microhabitats such as cavities, bark pockets, large dead branches, epiphytes, cracks, sap runs, or trunk rot that can be utilized by a variety of animals, plants, and fungi. Animal species use trees for shelter and food and include birds, small mammals, amphibians and reptiles, arachnids, and insects. Plants, lichens, and fungi can use trees as growing substrates or as a food source. Collectively, trees can be designed to act as corridors or small patches which can be utilized by a variety of animal species. Unlike forested ecosystems, urban trees and urban forests lack certain attributes, such as dead snags that offer shelter ([https://ufi.ca.uky.edu/wildlife-habitat-tree Miller] (accessed July 6, 2022); [https://www.ecolandscaping.org/02/designing-ecological-landscapes/trees/the-birds-and-the-trees-managing-the-urban-forest-for-wildlife/ Sundberg], 2019). | + | *[https://stormwater.pca.state.mn.us/index.php?title=Wildlife_habitat_and_biodiversity_benefits_of_Green_Stormwater_Infrastructure '''Habitat improvement''']: Individual trees can provide microhabitats such as cavities, bark pockets, large dead branches, epiphytes, cracks, sap runs, or trunk rot that can be utilized by a variety of animals, plants, and fungi. Animal species use trees for shelter and food and include birds, small mammals, amphibians and reptiles, arachnids, and insects. Plants, lichens, and fungi can use trees as growing substrates or as a food source. Collectively, trees can be designed to act as corridors or small patches which can be utilized by a variety of animal species. Unlike forested ecosystems, urban trees and urban forests lack certain attributes, such as dead snags that offer shelter ([https://ufi.ca.uky.edu/wildlife-habitat-tree Miller] (accessed July 6, 2022); [https://www.ecolandscaping.org/02/designing-ecological-landscapes/trees/the-birds-and-the-trees-managing-the-urban-forest-for-wildlife/ Sundberg], 2019). |
− | *[https://stormwater.pca.state.mn.us/index.php?title=Social_benefits_of_Green_Stormwater_Infrastructure Community livability]: | + | *[https://stormwater.pca.state.mn.us/index.php?title=Social_benefits_of_Green_Stormwater_Infrastructure '''Community livability''']: |
− | *[https://stormwater.pca.state.mn.us/index.php?title=Social_benefits_of_Green_Stormwater_Infrastructure Health benefits]: Health benefits of trees are well documented and include but are not limited to sequestration of harmful air pollutants (e.g. particulates), mitigation of summer heat stress, improved mental health and reduced stress, reduction in exposure to UV radiation, and positive clinical health (References: [https://www.nature.org/content/dam/tnc/nature/en/documents/Public_Health_Benefits_Urban_Trees_FINAL.pdf], [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345658/], [https://www.frontiersin.org/articles/10.3389/fevo.2021.603757/full]). Green spaces may also improve mental and physical health for residents and reduce crime (References: [17]; Barton and Rogerson, 2017). Studies suggest, however, that health benefits of trees may be limited to adaptive rather than mitigative effects, primarily due to limitations in space and structure of urban forests. | + | *[https://stormwater.pca.state.mn.us/index.php?title=Social_benefits_of_Green_Stormwater_Infrastructure '''Health benefits''']: Health benefits of trees are well documented and include but are not limited to sequestration of harmful air pollutants (e.g. particulates), mitigation of summer heat stress, improved mental health and reduced stress, reduction in exposure to UV radiation, and positive clinical health (References: [https://www.nature.org/content/dam/tnc/nature/en/documents/Public_Health_Benefits_Urban_Trees_FINAL.pdf], [https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345658/], [https://www.frontiersin.org/articles/10.3389/fevo.2021.603757/full]). Green spaces may also improve mental and physical health for residents and reduce crime (References: [17]; Barton and Rogerson, 2017). Studies suggest, however, that health benefits of trees may be limited to adaptive rather than mitigative effects, primarily due to limitations in space and structure of urban forests. |
− | *[https://stormwater.pca.state.mn.us/index.php?title=Economic_benefits_of_Green_Stormwater_Infrastructure Economic benefits and savings]: Benefits of trees discussed above provide economic value, for example, in the form of reduced cost of water quality or quantity treatment, improved health, recreation, and energy savings. Additional economic benefits include increased property values, job creation, and positive consumer outcomes. Several studies have attempted to quantify economic benefits of trees, with a wide range of results, but estimates are typically in the tens of billions of dollars (References: [https://conservationtools.org/conservation-benefits/131-Economic-Benefits-of-Urban-Trees-and-Green-Infrastructure], [https://www.sausalitobeautiful.org/economic-value-of-urban-trees/], [https://www.arborday.org/urban-forestry-economic/], [https://www.frontiersin.org/articles/10.3389/fevo.2020.00016/full#:~:text=Trees%20in%20urban%20areas%20have,pollutant%20formation%20in%20the%20atmosphere.]). | + | *[https://stormwater.pca.state.mn.us/index.php?title=Economic_benefits_of_Green_Stormwater_Infrastructure '''Economic benefits and savings''']: Benefits of trees discussed above provide economic value, for example, in the form of reduced cost of water quality or quantity treatment, improved health, recreation, and energy savings. Additional economic benefits include increased property values, job creation, and positive consumer outcomes. Several studies have attempted to quantify economic benefits of trees, with a wide range of results, but estimates are typically in the tens of billions of dollars (References: [https://conservationtools.org/conservation-benefits/131-Economic-Benefits-of-Urban-Trees-and-Green-Infrastructure], [https://www.sausalitobeautiful.org/economic-value-of-urban-trees/], [https://www.arborday.org/urban-forestry-economic/], [https://www.frontiersin.org/articles/10.3389/fevo.2020.00016/full#:~:text=Trees%20in%20urban%20areas%20have,pollutant%20formation%20in%20the%20atmosphere.]). |
− | *Macroscale benefits | + | *'''Macroscale benefits''': |
[[File:Central corridor final.jpg|thumb|300px|alt=photo for tree trench system, Central Corridor Light rail project|<font size=3>Photo of the completed tree system for the Central Corridor Light Rail Transit project, St. Paul, Minnesota. Image courtesy of the [http://www.capitolregionwd.org/ Capitol Region Watershed District].</font size>]] | [[File:Central corridor final.jpg|thumb|300px|alt=photo for tree trench system, Central Corridor Light rail project|<font size=3>Photo of the completed tree system for the Central Corridor Light Rail Transit project, St. Paul, Minnesota. Image courtesy of the [http://www.capitolregionwd.org/ Capitol Region Watershed District].</font size>]] |
Tree trenches and tree boxes are vegetated engineered landscape practices designed to filter or infiltrate stormwater runoff. They can be incorporated into a wide variety of landscaped areas, including ultra-urban landscapes. Technically, tree boxes and tree trenches are bioretention practices, but their design, construction, maintenance, and benefits merit a separate discussion. Note that this page does not discuss urban forests and use of trees in natural landscape settings. These are discussed on a separate page.
Green infrastructure (GI) encompasses a wide array of practices, including stormwater management. Green stormwater infrastructure (GSI) encompasses a variety of practices primarily designed for managing stormwater runoff but that provide additional benefits such as habitat or aesthetic value.
There is no universal definition of GI or GSI (link here fore more information). Consequently, the terms are often interchanged, leading to confusion and misinterpretation. GSI practices are designed to function as stormwater practices first (e.g. flood control, treatment of runoff, volume control), but they can provide additional benefits. Though designed for stormwater function, GSI practices, where appropriate, should be designed to deliver multiple benefits (often termed "multiple stacked benefits". For more information on green infrastructure, ecosystem services, and sustainability, link to Multiple benefits of green infrastructure and role of green infrastructure in sustainability and ecosystem services.
Benefit | Effectiveness | Notes |
---|---|---|
Water quality | Benefits are maximized for bioinfiltration. Biofiltration may export phosphorus if not designed properly. | |
Water quantity/supply | Bioinfiltration helps mimic natural hydrology. Some rate control benefit. | |
Energy savings | ||
Climate resiliency | Provides some rate control. Impacts on carbon sequestration are uncertain. | |
Air quality | ||
Habitat improvement | Use of perennial vegetation and certain media mixes promote invertebrate communities. | |
Community livability | Aesthetically pleasing and can be incorporated into a wide range of land use settings. | |
Health benefits | ||
Economic savings | Generally provide cost savings vs. conventional practices over the life of the practice. | |
Macroscale benefits | Individual practices are typically microscale, but multiple practices, when incorporated into a landscape design, provide macroscale benefits such as wildlife corridors. | |
Level of benefit: ◯ - none; ◔; - small; ◑ - moderate; ◕ - large; ● - very high |
Because of their diversity and use of vegetation, tree trench and tree box practices provide multiple green infrastructure benefits.
Tree trenches and tree boxes are bioretention practices. Therefore, design considerations to enhance green infrastructure benefits of tree trenches and tree boxes are similar to design recommendations for bioretention.
Maximizing specific green infrastructure (GI) benefits requires design considerations prior to constructing the practice. While site limitations cannot always be overcome, the following recommendations maximize the GI benefit of bioretetnion.
A tree ordinance is a tool to help protect and manage a community’s trees. It can be designed to regulate various aspects of tree planting, removal, and maintenance on public and private property within a municipality. For more general information on tree ordinances, link here: [18], [19], or [20].
An urban forest master plan provides a road map for managing trees and the tree canopy in an urban area. The master plan typically includes detailed information, recommendations, and resources needed to manage an urban forest. An important component of a good forest master plan is engaging citizens and other stakeholders in the value and care of the urban forest.
A master plan may contain some or all of the following elements.
Example master plans are found at the following links.