MOTU Missives | Philly’s Novel Approach to Urban Forest Management

This past spring, several MOTU staff members and interns had the opportunity to tour one of Philadelphia’s largest forests, 30-acre Haddington Woods, located on Cobbs Creek in West Philadelphia. Philadelphia’s forests provide a number of benefits to the city, e.g., storm water retention, localized cooling, and recreational opportunities. The Department of Parks & Recreation recently launched a multi-year forest management pilot in Haddington Woods, which is consistent with broader efforts to make the city more resilient in the face of a changing environment. Haddington Woods is open to the public. Check it out, and before you go, read about what MOTU learned on its tour:

It is well known that ecosystems around the world have been drastically altered by human activities. Many of these changes stem from climate change and the introduction of foreign species into ecosystems. In some cases, such as that of the Asian beetle, which is destroying ash trees across the U.S., invasive species compromise the growth of local species and create environmental imbalances; however, in other cases, the foreign species are harmless. This observation, along with the difficulties of eradicating alien species from compromised ecosystems has led to a change in the way that some conservationists and ecologists are approaching restoration.

Rather than attempting to remove all invasive species from an area, which is costly and in many cases ineffectual, some experts have shifted their focus to removing only foreign invasive species that are causing destruction to the compromised area. Importantly, this requires a great deal of management; the proliferation of an alien species that was not previously considered destructive can cause imbalances which later require its removal or reduction. Nonetheless, this novel approach to conservation is considered to be one of the most economically viable and realistic among conservationists in the long term. Rather than spend resources continually removing certain species, this approach acknowledges that because of climate change, species that will be assets to our urban forests today and in 20 years may not be those that were here 100 years ago.

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Our experts at the Ecosystem Management Group of Philadelphia Parks and Recreation (PPR) have adopted this theory and are putting it into practice at three large forest restoration sites in the park system. Together with the US Department of Forestry, local universities, the Pennsylvania Horticultural Society and other partners, PPR is conducting experiments to better understand how the forest management approach can improve the state of Philly’s urban forests. The effects of these experiments will be measured and monitored to better understand which management and decision-making processes are the most beneficial.

One of the main sites of this research is the 30 acre Haddington Woods at Cobbs Creek, which came into the Philadelphia park system in 1910. The plot includes forest areas, or “stand types”, of various qualities, which include (1) high quality forest; (2) intermediate quality forest; (3) degraded forest; and (4) an area of Black Alder, a tree species native to Europe.

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The high quality forest area has multiple layers of vegetation, including trees, shrubs, and a thick layer of leaves on the ground. The intermediate quality area features Buckeye and Catalpa trees, as well as Knotweed plants, which are an invasive species that will be removed. The degraded forest area is overgrown with vines which are severely compromising the trees and must be removed. For now, the area of Black Alder will remain as-is. Through these efforts, PPR is not only improving existing PPR assets, but also ensuring that Philadelphia’s park infrastructure remains resilient and sustainable.

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