Mapping an Urban Forest

Posted by: Bridget Dunn, Communications

“Is that a metal detector?”

“Does that thing track sound waves?

“Are you with Google Earth?”

Photo: Jeremy Dwyer-Lindgren/Woodland Park Zoo.

These are all questions that have been aimed at Michael Bradshaw in the last few months.  So what is he doing wandering Woodland Park Zoo grounds with a GPS and 7’ pole? You’ll probably never guess: He’s mapping trees!

Bradshaw, a forest science grad student at the University of Washington, is part of a project the zoo is very excited to finally tackle: creating a full inventory of the trees around our campus. This project will assess the health of our large urban forest through the evaluation of every tree on our grounds. Bradshaw is mapping trees and taking notes on their health, which is the first of three stages of this project. He does this work with special GPS mapping equipment which is accurate within 4-12”. This information is overlaid with other information about the zoo to create a detailed database for grounds management.  He anticipates finishing the map by spring. Using the info Bradshaw gathers, we will move onto the second stage of full, in-depth assessments of trees that might be in bad health. Finally, we will remove or prune any trees in failing health, with special attention to those that pose safety concerns for people and animals.

Photo: Jeremy Dwyer-Lindgren/Woodland Park Zoo.

This project is made possible by funds Woodland Park Zoo receives through the Seattle Park District, a 2014 voter-approved funding agreement created to address infrastructure needs at city parks. This important project, in addition to many others, has been backlogged for some time. With Park District funding, these critical projects will be completed over the next several years.

“Trees are an important element of the zoo, and an important element of the neighborhood,” noted Horticulture Supervisor David Selk. The zoo is unique in its dense tree coverage, not only in the local neighborhood, but among city parks. The zoo is 49-50% covered by its tree canopy, which consists of about 5,000 individual trees. The trees have gone under-recorded for a long time: the last census of the trees was completed over 20 years ago and had many inaccuracies. While there are records of all plantings for the last 20 years, there’s no record of what trees have died or been removed, so we’re not sure what’s actually growing on grounds. Creating an inventory of trees will enable us to improve the health of the entire forest.

Photo: Jeremy Dwyer-Lindgren/Woodland Park Zoo.

Some parts of the zoo have proved more difficult to map than others, or at least more time-consuming. The west plaza, home of the Humboldt penguin desert coast exhibit, went very quickly for an obvious reason—there aren’t a lot of trees there. Bradshaw mapped about 400 trees along the zoo’s west perimeter, including the plaza, in the course of a few days. By contrast, he’s mapped about 1,000 trees in the Northern Trail exhibit alone! The densely planted, relatively young pine forest of the Northern Trail took about two weeks. 

Mapping is further complicated by working around the animals’ schedules—we can hardly map the trees within the grizzly enclosure when Keema and Denali are out and about! Work is also slowed by heavy cloud coverage or dense foliage that interferes with communication between the equipment and the satellite. Some days, Bradshaw calls in Selk or other veterans of the horticulture team to help identify tropical trees not usually seen in the Pacific Northwest. 

Next time you’re at the zoo, keep an eye out for Bradshaw. Even if you don’t see him, take a moment to look beyond our animals to the rich forest they inhabit. And a big thank you to the voters of Seattle for approving the Park District, making it possible to maintain the health and safety of our grounds!

Photo: Jeremy Dwyer-Lindgren/Woodland Park Zoo.