[CANUFNET] tree canopy target

[Peter Duinker]

Greetings Alan:

Canopy targets for a city or town are, in my view, fairly arbitrary and definitely not generalizable.  I hold the view that targets are never scientifically based because they depend on people to express preferences and are therefore value-based.  The target-setting exercise can be scientifically informed, of course.  In the case of urban-forest canopy, one might expect an analysis of current canopy coverage and its benefits, as well as a range of forecasts detailing how many more trees it would take to get to a specific canopy coverage, and what would be the benefit stream associated with each scenario of canopy coverage.  I have never seen this done.

One could look at the question this way: what factors influence the setting of a canopy target?  Factors might include: (a) the current canopy, which is presumably lower than the target; (b) the cost, in terms of new trees established, to get to a specific canopy target at a particular future year; (c) the prospects that the cost predicted can be covered from the various budgets available; (d) the increase in benefits associated with the targeted canopy cover; and (e) what other cities and towns are doing in this respect.  While (a) through (d) are sensible factors, (e) is less so, but I'll bet that many urban-forest strategies are based on peer behaviour when it comes to canopy targets.  Perhaps it boils down to this: how much canopy cover would we ideally want?  Probably much, much more than we have today.  But how much canopy cover can we realistically hope to achieve in the next decades?  Probably some smallish fraction of the ideal.  So let's pick a number that seems achievable and gets us substantially more canopy than we have today.

I would be most interested to know if anyone is using a more sophisticated approach than this.

Best wishes, Peter Duinker

Peter N. Duinker, PhD, P.Ag.
Professor
School for Resource and Environmental Studies
Faculty of Management
Dalhousie University
6100 University Ave.
Halifax, Nova Scotia, Canada
B3H 4R2
Phone: 902-494-7100
Cell: 902-229-5141
Fax: 902-494-3728
Email: peter.duinker at dal.ca
http://www.dal.ca/faculty/management/sres/faculty-staff/our-faculty/peter-duinker.html

From: CANUFNET [mailto:canufnet-bounces at list.web.net] On Behalf Of Alan Kemp
Sent: June 21, 2016 1:11 PM
To: 'Canadian Urban Forest Network' <canufnet at list.web.net>
Subject: [CANUFNET] tree canopy target

The City of Nanaimo has an Urban Forest Management Strategy. In that Strategy we have a target of increasing our forest canopy to over 30% in the next decade. Of course this is difficult in the urban setting. Our Management and Protection of Trees Bylaw supports this document by requiring tree replacement plans for development, which in general terms works. However, I was asked why 30% or even 35%? What is the scientific reasoning behind that. Although I can explain all the benefits of an urban forest, I could not really give a good science based answer. I have looked through a lot of literature, but don't seem to be able to give a reasonable answer.

Any suggestions?

Alan Kemp
Urban Forestry Coordinator
Certified Arborist, Certified Tree Risk Assessor
Community Development
City of Nanaimo
250 755 4460 (local 4357)
alan.kemp at nanaimo.ca<mailto:alan.kemp at nanaimo.ca>
www.nanaimo.ca/goto/urbantrees<http://www.nanaimo.ca/goto/urbantrees>


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