How are Street & Park Trees managed in Louisville?
Louisville Public Tree Inventory
Canopy Coverage is one data set that helps us understand the density and spread of Louisville's urban forest. However, it does not give us all the information. What types of trees is the urban forest made up of? What condition are they in?
A public tree inventory collects and stores information about trees on public land including tree type, size, condition, and other site information. This information is collected by visiting each tree on public land and storing information as a data point in a GIS-based tree management software system. This information is critical to managing public trees effectively and is considered a best management practice to have a full inventory of all publicly managed trees in the community that contains current data that is updated on a consistent schedule.
Louisville Urban Forestry has been working since 2016 to collect inventory data. All trees in managed landscaped areas of Parks and Parkways are collected, and staff is working to collect information on public street trees.
A public tree inventory collects and stores information about trees on public land including tree type, size, condition, and other site information. This information is collected by visiting each tree on public land and storing information as a data point in a GIS-based tree management software system. This information is critical to managing public trees effectively and is considered a best management practice to have a full inventory of all publicly managed trees in the community that contains current data that is updated on a consistent schedule.
Louisville Urban Forestry has been working since 2016 to collect inventory data. All trees in managed landscaped areas of Parks and Parkways are collected, and staff is working to collect information on public street trees.
Understanding the Urban Forest
With limited resources, Louisville Urban Forestry is focusing data collection on trees that require maintenance and newly planted trees. This means that, while progress toward a complete inventory is being made, the data is currently incomplete and can not give us an accurate picture of the make-up of Louisville's public trees.
Street Tree Inventory: Approximately 10,000 trees collected, and 13,000 potential planting sites.
Parks Tree Inventory: Approximately 33,000 trees collected.
Data Gaps:
Street Tree Inventory: Approximately 10,000 trees collected, and 13,000 potential planting sites.
- Very limited data- estimated 2% of public trees collected.
- Data collection is currently limited to dead/diseased/maintenance needed trees and newly planted trees.
Parks Tree Inventory: Approximately 33,000 trees collected.
- Information is updated on trees that have received maintenance and newly planted trees.
- Trees that have not needed maintenance have not been updated since the information was first collected, meaning that much of this data is out of date.
Data Gaps:
- Inventory information is incomplete.
- No data on city-owned natural areas and woodlands. (This is common, as these trees are not maintained to the level that trees in managed and landscaped areas are maintained.)
- No data on private trees. (Again, this is common.)
How is inventory data used to improve the urban forest?
How much we know about our urban forest is wholly dependent on the data available to us. We know that there are gaps in our knowledge that prevent us from developing an accurate understanding of the make-up of Louisville's urban forest. Understanding where those gaps are is an important step in planning for improvements to fill those gaps.
With complete inventory information, Louisville would be able to develop an accurate picture of the current state of their urban forest, including species diversity, age diversity, condition of trees, and site suitability (trees in locations that are suited to their size and needs).
Let's examine why each of these factors is important to our understanding of the health and longevity of the urban forest.
We'll use the Louisville parks tree population as an example, with the understanding that this data is somewhat out of date and does not represent Louisville's entire urban forest.
With complete inventory information, Louisville would be able to develop an accurate picture of the current state of their urban forest, including species diversity, age diversity, condition of trees, and site suitability (trees in locations that are suited to their size and needs).
Let's examine why each of these factors is important to our understanding of the health and longevity of the urban forest.
We'll use the Louisville parks tree population as an example, with the understanding that this data is somewhat out of date and does not represent Louisville's entire urban forest.
Age (Size) Distribution:
A sustainable urban forest is one that maintains the flow of tree benefits over time. This means that there should be a good mix of different sizes (ages) of trees so that as some trees age out, others are actively growing to take their place.
Ideal distribution is shown as the orange dotted line in the chart to the right. Generally, a renewable urban forest should have a mix of tree ages with young trees making up the largest portion (40%) of the urban forest. A strong population will exceed losses and ensure continuation of tree benefits. Preserving large trees is also important, as we know that larger trees provide more benefits.
Note: Size of trees is not complete accurate indication of tree ages, as different species grow at varying rates and have varying mature sizes. However, it is close enough to provide an accurate picture of approximate distribution of ages.
A sustainable urban forest is one that maintains the flow of tree benefits over time. This means that there should be a good mix of different sizes (ages) of trees so that as some trees age out, others are actively growing to take their place.
Ideal distribution is shown as the orange dotted line in the chart to the right. Generally, a renewable urban forest should have a mix of tree ages with young trees making up the largest portion (40%) of the urban forest. A strong population will exceed losses and ensure continuation of tree benefits. Preserving large trees is also important, as we know that larger trees provide more benefits.
Note: Size of trees is not complete accurate indication of tree ages, as different species grow at varying rates and have varying mature sizes. However, it is close enough to provide an accurate picture of approximate distribution of ages.
Diversity:
Pests and diseases often target one genus or group of trees, so having a diverse urban forest made up of many different species of trees is important for health and longevity. To avoid significant losses in the future, best management practices tell us not to exceed:
Again, this data is limited to parks trees and is somewhat out of date, so we expect this to change as data collection continues and updates are consistent. However, the chart to the right shows an excellent diversity of species, with all recorded species well below the recommended 10% maximum.
Pests and diseases often target one genus or group of trees, so having a diverse urban forest made up of many different species of trees is important for health and longevity. To avoid significant losses in the future, best management practices tell us not to exceed:
- 30% in one Family
- 20% in one Genus (Oaks for example)
- 10% in one species (White Oak)
Again, this data is limited to parks trees and is somewhat out of date, so we expect this to change as data collection continues and updates are consistent. However, the chart to the right shows an excellent diversity of species, with all recorded species well below the recommended 10% maximum.
Diversity by Genus and Family:
- Only the Oak Genus is slightly over the recommended 20% of the total population.
- All recorded tree Families are under the recommended 30% of the total population.
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Condition of Trees:
A detailed understanding of the condition and risk potential of all publicly owned trees is critical. Condition is an important indicator of:
As discussed, Louisville has a full inventory of trees in parks, but that inventory is only updated when maintenance is performed or new trees are planted. The current condition of trees that have not received maintenance can be considered unknown, as the data is about ten years old and we know that trees grow and change over time.
A detailed understanding of the condition and risk potential of all publicly owned trees is critical. Condition is an important indicator of:
- Risk to citizens.
- Future needs of tree canopy
As discussed, Louisville has a full inventory of trees in parks, but that inventory is only updated when maintenance is performed or new trees are planted. The current condition of trees that have not received maintenance can be considered unknown, as the data is about ten years old and we know that trees grow and change over time.
You can find information on how Louisville Metro manages public trees, including rules and regulations and contact information, as the Louisville Urban Forestry page.
