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Category Archives: urban forests

Why urban natural areas matter

Questions raised by urban development in Peterborough Ontario apply to many municipalities

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A 250-year-old cedar tree near Jackson Creek

A few months ago I used growth ring counts to age trees in an old-growth forest in the path of Peterborough’s parkway extension. The oldest trees I found near Jackson Creek are about 250 years old, and some of these will be destroyed if the parkway bridge is built. This raises questions about Peterborough’s values as a community – simply put (leaving aside the oft-debated cost of a bridge, and whether it is needed), is an old-growth forest as important as a bridge? Many North American urban areas are grappling with similar questions. In Peterborough it’s a parkway across an old growth forest; in Niagara Falls Ontario it’s wetlands in the path of a golf course development. The proposed developments and the natural areas are different, but most municipalities have been there before, and will be again, so what can we learn from the Peterborough example?

The seemingly irreconcilable value systems that inform Peterborough’s parkway debate originate in part from incomplete information. One question that has been raised, whether the old-growth forest in Jackson Park would be impacted by a bridge, is easily answered: yes. Some of the oldest trees will certainly be destroyed, and over a third of the old-growth stand could be significantly impacted. Whether the forest will be impacted is not really in dispute, as the city’s own Environmental assessment lists a variety of likely impacts on the forest.

A more difficult question is ‘does it matter?’ While this is ultimately a question of values, science does have something to contribute to the discussion. Some of the rationales for valuing important urban natural areas include historical continuity, biodiversity conservation, and human well-being.

Over the past decade or more the concept of heritage trees, similar to heritage buildings, has been promoted by organizations such as the Ontario Urban Forest Council. This is a formal recognition of the cultural and emotional connection that we feel towards trees. Would we knock down a number of the oldest buildings in Peterborough to build a bridge? Likely not. What about trees that started growing in 1760, and are significantly older than the oldest buildings? While historical cultural use of Jackson Park has been referenced in the parkway process, the heritage value of the trees themselves has not been considered.

Biodiversity is a broad term encompassing the diversity of ecosystems, species within the ecosystems, and genes within the species. It is important for many reasons, not least of which is the resiliency it provides in response to threats such as climate change, introduced species, pollution etc. Urban biodiversity has long been undervalued, but new research has shown that the biodiversity of urban areas is quite high, and can be comparable to surrounding landscapes. This may surprise you because urban areas are obviously a fragmented disturbed environment, but so is much of the surrounding landscape. Urban parks can be surprisingly intact, and have high biodiversity value. Examples in Peterborough include the old-growth forest in Jackson Park, and the wetlands and cold-water trout stream in Harper Park.

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Jackson Creek Forest in relation to the Big Picture 2002

In order to conserve the biodiversity of urban natural areas, which are often small, we should ensure they are connected so that species and genes can flow between them. The Jackson Creek Valley has been recognized in reports as an important natural linkage. Forest and provincially significant wetland surround Jackson creek, and are contiguous to the Cavan Swamp, a large natural area just west of town, which in turn has natural linkages extending to the Oak Ridges Moraine and beyond. We no longer think of our natural areas in isolation, but rather as part of much larger natural areas networks.

We invest time and money to identify and map natural area networks with the idea that they should be protected from development whenever possible, but these maps may not even be consulted in development decisions. Municipalities have a lot of authority and responsibility in natural heritage conservation in southern Ontario, but this is only sometimes recognized and acted upon. One of the primary provincial policy mechanisms to protect biodiversity in Southern Ontario is the 2014 Provincial Policy Statement (PPS). However the Environment Commissioner of Ontario concluded that the PPS “is wholly inadequate to safeguard natural heritage against the irreparable damage and loss of biodiversity that inevitably accompany development.” The PPS has few teeth to compel municipalities to meet their obligations to designate and protect natural heritage features and the linkages between them. That said, a plan to develop a parkway through a 250-year-old urban forest is, as far as I know, unprecedented in modern Ontario. It will be interesting to see how things play out in Peterborough.

If it gets that far. Public sentiment hasn’t generally favoured the bridge option in Peterborough’s parkway plan, largely because people love the park. This brings us to the final rationale for conserving urban natural areas: human well-being. For as long as people have built cities they have included parks, trees, and greenspaces within them, and this is not accidental. The concept that humans are genetically predisposed to have an affinity for nature is called the biophilia hypothesis. Numerous recent studies have concluded that exposure to nature offers wide ranging health benefits, including stress relief, increased pain tolerance, and generally improved health outcomes. In this context, preserving intact green spaces is a public health imperative.

20160329_162146In the absence of strong provincial policy on these questions, it usually falls on municipal councils to make decisions that impact our ecological legacy. Councillors should consider this responsibility when voting on municipal affairs, and members of the public should be aware when they vote for councillors and mayors that some of the most important environmental decision making takes place at the municipal level.

Like most municipalities, Peterborough’s system of natural areas exists in part by chance, but largely because of choices made by past generations. The question now is what will we do with it? What will our grandchildren inherit; and are they more likely to thank us for a parkway bridge, or an intact valley and old-growth forest in the heart of the city?

Update: In September 2016 the Province ordered a full environmental assessment of the Peterborough parkway, citing the bridge through Jackson Park as a primary reason for the bump up.


Michael Henry is an ecologist with the non-profit organization Ancient Forest Exploration & Research, and author of the book Ontario’s Old-Growth Forests. He was the lead researcher on a study of the Jackson Creek Old-Growth Forest, available online at www.ancientforest.org/jackson-creek-old-growth-forest/.