Urban Tree Vulnerability in Residential Toronto, Ontario, Canada

Summary: An article in Arboriculture & Urban Forestry January 2019 adds urban tree vulnerability to urban forest management functional and structural assessments.

A study of publicly-owned trees during the 2014 growing season in the Downtown Toronto neighborhood of Harbord Village revisited a 2007-2008 inventory of publicly-owned trees (i.e., street, front-yard rights-of-way, park and schoolyard trees) to assess vulnerability; bay-and-gable-styled houses in Harbord Village; Friday, Jan. 16, 2009, 17:29: SimonP, CC BY SA 3.0 Unported, via Wikimedia Commons

An article in the Arboriculture & Urban Forestry January 2019 issue assesses publicly owned residential urban tree vulnerability for 806 specimens in Toronto, Ontario, Canada, through inventories in 2007/2008 and in 2014.

Andrew Millward, David Nowak, Pamela Robinson, Sandy Smith and James Steenberg broach high building density, human population, impervious surfaces, stressor-friendly commercial land use and tree mortality. Their article, A Social-Ecological Analysis of Urban Tree Vulnerability for Publicly Owned Trees in a Residential Neighborhood, concerns stress-caused decline in urban forest ecosystem service supply. Urban tree vulnerability assessments discern building, ground-cover, lighting, sidewalk and street exposures; building, infrastructure, sidewalk and utility conflicts; and social stressors such as mismanagement and vandalism.

A proper framework for analyzing urban tree vulnerability examines age-, condition-, size-, structure-determined sensitivity and adaptive capacity after exposure to externally caused systemic disturbances and stressors.

Exposure indicators feature more indirect relationships between ecosystem stress and surroundings than such direct stressors as vandalism within the Deciduous Forest Region and Mixedwood Plains Ecozone.

Saplings; species, not necessarily Toronto's green ash, honey-locust, horse-chestnut, Manitoba maple, Norway maple, silver maple, tree-of-heaven, white cedar and white mulberry; and transplants garner high mortalities. The study's 400- to 700-people dissemination areas, smallest census and National Household Survey geo-units, harbor canopy-cover, education, green-space, income, ownership, stewardship and value adaptive capacity indicators. Researchers in Halifax, Nova Scotia, in Syracuse, New York, and in Toronto, Ontario, invoked artificial, biological brain-like, multilayer perceptron neural network (MPNN) algorithms and data structures.

One Dalhousie University, one State University of New York, one University of Toronto and two Ryerson University researchers judged MPNN judicious for tree mortality morphological parameters.

Supervised learning-keyed error values kindled final weight values of vulnerability indicators and predictive capacity for tree mortality by MPNN, known from artificial intelligence and computer science.

The five researchers listed two-thirds of the MPNN-logged data records as training samples, to limit overfitting models and generating incorrect results, and one-third as testing samples. Their study mentions adjacent commercial buildings and commercial land uses as most detrimental to urban tree health through maximum exposure and urban tree decline and mortality. Urban tree vulnerability assessments need to note among physical and social exposures such biological exposures as emerald ash borer-provoked green ash (Fraxinus pennsylvanicus) decline and mortality.

Tree size offers urban tree vulnerability assessments an interactor with exposures and a predictor of tree condition, itself a predictor of diameter growth and of mortality.

Age-associated tree decline perhaps predicts mature, sensitive urban tree vulnerability in established, older neighborhoods and presents processes behind tree decline and tree mortality as sometimes non-overlapping.

Household-scale, qualitative research queues up potential insights into the array of social processes that quicken adaptive capacity, semi-reluctant indicator of ecological change and urban tree vulnerability. Long-lived, mature trees with large leaf areas and trending low age and species diversity respectively realize high-level ecosystem services and age-, pest-, storm-sensitive urban tree vulnerability. Urban tree vulnerability science serves to strengthen research into functional and structural loss, risk and tree safety in such highly, complex, social-ecological systems as urban forests.

Testing Toronto's dogwood, eastern red cedar, Freeman maple, Japanese maple, mugho pine, serviceberry and white cedar takes managing ecosystem function and structure into urban tree vulnerability.

An urban tree vulnerability study during the 2014 growing season revisited the Downtown Toronto neighborhood of Harbord Village, where a tree inventory had been conducted in 2007-2008: HarbordVillage @HarbordVillage, via Twitter Nov. 28, 2018

Acknowledgment

My special thanks to:
talented artists and photographers/concerned organizations who make their fine images available on the internet;
University of Illinois at Urbana-Champaign for superior on-campus and on-line resources.

Image credits:

A study of publicly-owned trees during the 2014 growing season in the Downtown Toronto neighborhood of Harbord Village revisited a 2007-2008 inventory of publicly-owned trees (i.e., street, front-yard rights-of-way, park and schoolyard trees) to assess vulnerability; bay-and-gable-styled houses in Harbord Village; Friday, Jan. 16, 2009, 17:29: SimonP, CC BY SA 3.0 Unported, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Harbord_Village.JPG

An urban tree vulnerability study during the 2014 growing season revisited the Downtown Toronto neighborhood of Harbord Village, where a tree inventory had been conducted in 2007-2008: HarbordVillage @HarbordVillage, via Twitter Nov. 28, 2018, @ https://twitter.com/HarbordVillage/status/1067884563018346496

For further information:

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Steenberg, James W.N.; Andrew A. Millward; David J. Nowak; Pamela J. Robinson; and Sandy M. Smith. January 2019. "A Social-Ecological Analysis of Urban Tree Vulnerability for Publicly Owned Trees in a Residential Neighborhood." Arboriculture & Urban Forestry 45(1): 10-25.