Good Inventory, Good Results
An inventory [no more than four years old] will reveal the age, species, size and condition of the trees you’ll be managing. It will also serve as the foundation for your longer-term maintenance plan.
Top-Down or Bottom-Up?
You can take inventory with data you collect “on the ground” literally looking at the trees themselves or with overhead images captured by airplanes, satellites, even drones! Your choice will depend on what you hope to learn, and how much you can afford to spend to get it. Most communities do some of both.
Do I Really Need to Look at Every Tree?
Actually, no. Sample based inventories, whether top-down or bottom-up, will provide a solid [and statistically valid] foundation for growing and managing your urban forest. Complete inventories are usually limited to specific areas where you need critical information about tree conditions. Communities afflicted by emerald ash borer or other pests, for example, often inspect tree by tree.
What if I want to track change over time?
An inventory represents a static snapshot, and can be used to assess species composition, present maintenance needs, and manage tree crew workflows. But understanding change over time – such as changes in total tree counts, tree mortality rates, or tree growth rates – requires careful monitoring. Check out resources from the USDA Forest Service about urban tree monitoring.
Who Can Do the Work?
Well, urban foresters and arborists can certainly do the work. But that’s expensive. Many communities rely on trained volunteers and students to conduct sample-based inventories. Special software and training programs prepare “citizen stewards” to examine trees and report on their condition. Other tools – some free, some not – can aggregate the data and provide detailed reports on the condition of your urban forest.
Training materials often include maps and street views loaded on smart phones to help guide volunteers as they develop a representative sample of trees in their community. Check out PlanIT Geo Tree Plotter app; it’s used in many volunteer programs around the country. Or try OpenTreeMap, software designed for community-based urban forestry programs.
In the District of Columbia, the Urban Forestry Administration and Casey Trees have created and help maintain a city-wide map of the City’s roughly 145,000 street trees. The aim? To help the public understand the forest that surrounds them, and to encourage citizen engagement in stewardship of street trees.