UFFU Conference 2022 - Science Day Book of Abstracts

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SCIENCE

DAY 1 27—06—22

BOOK OF ABSTRACTS

SCIENCE

© COPYRIGHT KU LEUVEN — 2022 — Without written permission of the publishers it is forbidden to reproduce or adapt in any form or by any means any part of this publication. Requests for obtaining the right to reproduce or utilize parts of this publication should be addressed to Faculty of Engineering and Department of Architecture, Kasteelpark Arenberg 1 box 2431, B-3001 Heverlee.

A written permission of the publishers is also required to use the methods, products, schematics and programs described in this work for industrial or commercial use, and for submitting this or part of this publication in scientific contests.

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ISBN — 978-9-46444-723-1 — 1 / 3

I N T E R N AT I O N A L C O N F E R E N C E — L E U V E N

URBAN FORESTS FOREST URBANISMS & GLOBAL WARMING —

Developing Greener, Cooler & more Resilient Cities

DAY 1 | SCIENCE 27—06—22 — The day will concentrate on insights from earth, environmental and related sciences—particularly ecology, forestry, soil science, geology, and environmental psychology. It will focus on empirical and evidence-based approaches that support policies, programmes, and projects.

Research from across the world will highlight the state-of-the art in the interdisciplinary field of urban forestry, particularly with regards to climate change mitigation and adaptation to global warming.

DAY 1 PROGRAMME SCIENCE

08.30 REGISTRATION & COFFEE 09.00 INTRODUCTION & WELCOME 09.15 — 10.55

SCIENCE EXPERT PANEL Moderator: Bart Muys

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09.15

CECIL KONIJNENDIJK

→ 10

Reforesting the City in Times of Global Change: Providing evidencebased guidance 09.35

AM —

CHRISTIAN MESSIER

→ 12

Novel Tools and Approaches to Manage Green Spaces in Urban and Peri-urban Areas for Resilience 09.55

CYNNAMON DOBBS

→ 14

Demand and Supply of Urban Forest Ecosystem Services: Are expectations fulfilled?

10.15

COLLEEN MURPHY-DUNNING

→ 16

Promoting Inclusive Urban Forestry: Scaling from population data to engaging people 10.35

RIK DE VREESE

→ 18

Urban Forests as Nature-based Solutions: Public perceptions in Europe and China

Scan here for latest programme updates

10.55 — COFFEE 11.15

MODERATED DISCUSSION

12.30 LUNCH BREAK

13.30 — 16.30

PARALLEL SCIENCE PAPER SESSIONS

EVIDENCE-BASED URBAN FOREST MANAGEMENT & PLANNING Moderator: Francesc Baró

CLIMATE SMART URBAN FORESTS: WHAT & HOW? Moderator: Ben Somers

ANDREA HIOTT FT

SASKIA DE WIT FT

SOMIDH SAHA

FANNY MAURE PK

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PK

BULENT OZEL PK

KAREN DE PAUW PK

MAIDER LLANGUNO-MUNITXA PK

SONIA LE MENTEC PK

AGATHA CZEKAJIO PK

RITA SOUSA-STELLA PK

TOM CORNU PK

ANNALISA METTA PK

DISCUSSION

DISCUSSION

16.30 — COFFEE

16.45 — 17.45

ROUND TABLE OF EXPERTS

17.45 — WALK TO LEUVEN TOWNHALL 18.00

LEUVEN CITY WELCOME

by Elderman David Dessers

18.15 RECEPTION

FT = Full Talk 15‘ + 10‘ Response

SCI II → 28

PK = Pecha Kucha 20“ x 20 Slides + 10‘ Response

SCI I → 20

— PM

NOTES —

SCIENCE EXPERT PANEL — Moderation:

BART MUYS Earth and Environmental Sciences, KULeuven

CECIL KONIJNENDIJK CHRISTIAN MESSIER COLLEEN MURPHY-DUNNING RIK DE VREESE

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—8

CECIL KONIJNENDIJK — Director, Nature Based Solutions Institute Program Director (Master of Urban Forestry Leadership), University of British Columbia Cecil has extensive experience in urban forestry and nature-based solutions. Since 2016 he has been a professor of urban forestry at the University of British Columbia in Vancouver. Cecil co-foundthe academic journal Urban Forestry & Urban Greening, and edited seminal textbooks including The Routledge Handbook of Urban Forestry. Cecil is passionate about using trees and nature to develop better cities, and stresses the importance of meaningful relationships between people and places. He has advised international organisations such as the United Nations, as well as various national and local governments. He currently lives in Barcelona from where he co-leads the Nature Based Solutions Institute, a think tank that supports the evidence-based greening of cities across the world.

Recent years have seen increasing attention of the role of trees and other vegetation as nature-based solutions, for example in efforts to adapt cities to the impacts of climate change. Planting trees is not enough, as urban forests can only thrive if good management and stewardship are in place. This contribution will discuss how evidencebased, locally-grounded urban forestry can be successful in bringing the forest back into urban settings. Particular focus will be on the analysis of successful governance and stewardship approaches, and on the role that communicative guidelines like the 3-30-300 rule for greener cities can play.

REFORESTING THE CITY IN TIMES OF GLOBAL CHANGE — Providing evidence-based guidance

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CHRISTIAN MESSIER — University of Québec, Montréal (UQAM), Outaouais (UQO)

Christian is professor of Forest Ecology and scientific director at the University of Quebec, in Canada (UQO and UQAM) since 1992. His expertise is in developing innovative urban and natural forest management approaches from tree to landscape scales to increase the resilience of forests to global change. He collaborates with researchers from around the world and is involved in many international research networks. He holds an industrial-NSERC research Chair on tree growth since 2010 and a Canada Research Chair on the resilience of managed forest to global change since 2017. He was recently inducted to the Royal Society of Canada.

Urban and peri-urban forests are vulnerable to various threats, from residential development to global change stressors such as climate change and invasive pests and diseases. His presentation will present a number of novel approaches and tools being developed from tree to landscape scales to assist urban foresters. At the tree level, mobile LiDAR scanning tools help to assess tree growth and pruning requirements. At the stand level, functional diversity framework guides tree plantation to increase resilience to global stressors. Finally, at the landscape scale, network theory can optimise interventions at large spatial scales.

NOVEL TOOLS & APPROACHES TO MANAGE GREEN SPACES IN URBAN & PERI-URBAN AREAS FOR RESILIENCE

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COLLEEN MURPHYDUNNING — Director, Hixon Center for Urban Ecology Director, Urban Resources Initiative (URI), Yale School of Environment (YSE)

Colleen received her B.S. in Public and Environmental Affairs from Indiana University, and M.S. in Forestry from Humboldt State University.

At Yale’s Urban Resources Initiative, she and her colleagues carry out community-driven urban forestry to improve both the social and physical environment of the City of New Haven. Colleen also administers the Hixon Center Fellowship program to support graduate students conducting a wide range of research projects in cities across the globe and co-leads a field-based urban ecology module for all incoming YSE graduate students.

A challenge of bridging science to practice is scaling research data sets to fit urban forestry management needs.

Coupling population data with risk data on urban heat island or flooding reveal patterns of vulnerability but are produced at a coarse scale that can be challenging to match the scale of urban forestry decision-making.

The presentation will share the use of research data to inform urban forestry management while also practising community-scale urban forestry to engage residents.

PROMOTING INCLUSIVE URBAN FORESTRY —

Scaling from population data to engaging people

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RIK DE VREESE — Urban Forestry Team Leader with the Resilience Programme at the European Forest Institute (EFI) Member of the International Steering Group of the European Forum on Urban Forestry (EFUF)

Rik studied forestry at Ghent University and received his PhD in Human Ecology at the Vrije Universiteit Brussel (VUB). He is coordinating the Horizon 2020 research project “CLEARING HOUSE” which focuses on urban forests as nature-based solutions in Europe and China. His research investigates the relations between humans and trees, in both the urban and peri-urban spheres.

More specifically, Rik has been involved in research on integrating ecosystem services in governance, decision-making and urban planning, mainly with a transdisciplinary lens.

The presentation will discuss results from the CLEARING HOUSE project which surveyed public perceptions on urban forests and urban trees in European and Chinese cities. Insights from this perception study will help to shape urban forests that meet public demands. The study shows that people prefer cultural and regulating above provisioning ecosystem services of urban forests. The most sought-after ecosystem services were air quality, habitat and aesthetics. However, around ten percent of respondents do not visit parks or forests, nor have the willingness to do so, with time, distance and lack of general interest being the primary barriers.

URBAN FORESTS AS NATURE-BASED SOLUTIONS —

Public perceptions in Europe & China

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NOTES —

SCIENCE SESSION I EVIDENCE-BASED URBAN FOREST MANAGEMENT & PLANNING

— Moderation: FRANCESC BARÓ Department of Geography, VUB ANDREA HIOTT Reorienting Ecologically.

SOMIDH SAHA Inter-and transdisciplinary Research Approaches to Increase the Resilience of Urban and Peri-urban Forests (UPF) to Climate Change Impacts.

BULENT OZEL Trees as Infrastructure (TreesAI).

MAIDER LLAGUNO-MUNITXA Pedestrian Level Green Infrastructure Survey.

AGATHA CZEKAJLO Urban Greening Versus Urban Densifications.

TOM CORNU

Urban forests are diverse and complex ecosystems which require holistic and interdisciplinary assessment and planning approaches. This session brings together new frameworks, tools and evidence-based insights from different case studies to understand and manage the urban forest so its benefits for people (and other species) are fully realized.

The Impact of Urban Greenspaces on Heat-related Mortality in Elderly.

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Reorienting Ecologically. Why urban forests are optimal.

Andrea Hiott — Berlin School of Mind and Brain, Humboldt Universität zu Berlin, Brandenburg University of Technology, Doeller Lab (Max Planck Institute), Northoff Lab (University of Ottawa) cognition — landscape — navigation

Inter-and Transdisciplinary Research Approaches to Increase the Resilience of Urban and Peri-urban Forests (UPF) to Climate Change Impacts. Lessons learned from the first phase of the “GreenLung” (“GrüneLunge”) project, Germany.

scales — heuristics Somidh Saha (1)(2), Andreas Matzarakis(3), Axel Albrecht(4), Annika Fricke(1), Fabian Collet(5), Iulia Almeida(1), Mareike Hirsch(4,6), Marcel Gangwisch(3), Jessica Maria CuevaGiron(1,7), Mario Köhler(5), Angela BeckmannWübbelt(1), Mia Schobert(1), Katrin Fröhlich(1), Helena Trenks(1), Oliver Parodi(1), Helena Böddeker(4), Ulrich Kienzler(8), Martin Reuter(9) — (1) Institute for Technology Assessment and

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There has been productive debate over how we define our cities. Still, the default public assumption is to contrast urban and nature, to assume these terms are opposites rather than kin. Part of this stems from a wider dichotomy opposing physical to mental and body to mind. Such concepts measure scales of complexity within the same process, but our lack of a clear interdisciplinary definition of cognition keeps us from applying this ecologically.

Towards reorientation, and inspired by recent developments in cognitive neuroscience, this paper frames cognition as means of wayfinding, forms of navigation afforded by encountered regularities. This means human cognition (thinking, remembering, etc.) is continuous with other forms of bodily navigation. It also means landscape includes all sensory, spatiotemporal encounters. Understanding this reorients nature and urban from both sides and provides clear reasoning for championing urban forests. It also clarifies heuristics for designing and aligning green environments.

Systems Analysis (ITAS), Karlsruhe Institute of Technology (KIT). (2) Chair of Silviculture, Albert-Ludwigs University of Freiburg. (3) Research Center Human Biometeorology, German Meteorological Service. (4) Department of Forest Growth, Forest Research Institute of Baden-Wuerttemberg. (5) City Horticulture Department of Karlsruhe. (6) Chair of Forest Growth and Dendroecology, Albert-Ludwigs University of Freiburg. (7) Land Surveying Office of City Darmstadt, Section Cartography.

(8) City Forest Department of Karlsruhe. (9) Section Environment and Local Agenda, City of Rheinstetten. trade-offs — urban forest health — urban forest growth — tree species selection — covid-19

The concurrent increase in the supply of ecosystem services and resilience in UPF warrants involving multiple stakeholders and disciplines. Therefore,

we applied holistic inter-and transdisciplinary research approaches in the “GreenLung” (“GrüneLunge”) project (2018-2023, https://www. projekt-gruenelunge.de/), aiming to increase the resilience of the UPF to climate change impacts in Karlsruhe and Rheinstetten, southwest Germany.

We executed an inventory and health survey by installing 201 random circular plots (404 m² each) in the study area. Further, we sampled City Tree Register’s (CTR) trees for dendroecological, dendrochemical (C, O, and N stable isotopes), biodiversity, and meteorological analyses. During heatwave conditions, mobile measurements allowed to study the thermal influence of land use, urban morphology, tree species density, and diversity to atmospheric conditions. A participatory map-based questionnaire survey with the respondents from the two cities was carried out to identify the perceptions of cultural ecosystem services, especially during the COVID-19 pandemic. During a series of excursions, training, expert meetings, and workshops in real-world labs (“reallabor “) with citizens and stakeholders, we identified possible solutions for improving the current management of UPF. Our study revealed a significant trade-off between supporting and regulating ecosystem services.

High crown dieback was observed in surveyed trees. An increase in drought tolerance at the species level reduced the magnitude of dieback in our study area. A high number of exotic trees showed a lower level of dieback. However, exotic oak species (Quercus rubra), for example, had less microhabitat diversity, abundance, and bat activities than native oaks (Quercus robur). Dendroecological and stable isotope analyses revealed high plasticity on climate-growth relationships between species.

Quercus robur and Platanus hybrids had the highest tolerance level to periodic events of droughts.

Carpinus betulus had a moderate level, whereas Tilia cordata and Acer platanoides showed a poorer drought tolerance. We did not find any clear evidence on the negative effect of NOx pollution on stem growth. The relative air temperature (2m from the surface) cooled down with increasing vegetation

cover during night and morning during heatwaves.

Increasing tree species diversity resulted in cooling during heatwaves. Tilia cordata and Carpinus betulus positively influenced the cooling, but it was not influenced by other tree species such as Acer platanoides and Quercus robur. The participatory map-based questionnaire survey revealed a high public appreciation of cultural ecosystem services.

During the pandemic, especially citizens without access to private gardens and balconies visited public green spaces more often to reduce psychological stress. A series of transdisciplinary dialogues with citizens and stakeholders revealed the areas of improvement in tree care. For instance, a sensorbased intelligent irrigation system for urban trees was designed to increase watering efficiency. The project’s first three years were spent researching and developing possible solutions to increase the resilience of the UPF, whereas the next two years of the project will be used to implement the research findings in practice. The research and development phase findings will be presented at this conference.

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Trees as Infrastructure (TreesAI).

Scenario analysis framework.

Bulent Ozel, Aaron Gillet, Arianna Smaron, Axel Nilsson, Carlotta Conte, Carolina Christiansen, Cloe Treger, Dana Balibanu, Gurden Batra, Indy Johar, Konstantina Koulouri, Marko Petrovic, Sofia Valentini, Oguzhan Yayla, Raj Kalia — Dark Matter Laboratories, Lucidminds.ai agent-based modeling — urban forest — digital twins — nature-based solutions — scenario analysis

introduces a novel scenario analysis framework (SAF) that enables to design, forecast, and monitor green infrastructure portfolios and their impacts (over 50+ years) under varying weather conditions, maintenance regimes, species compositions of tree populations, their spatial distributions and their exposure to diseases.

The framework is based on an agent-based modeling (ABM) and simulation paradigm, enabling to embed a green infrastructure portfolio within ecological, topographic, economic and social configurations of a city. ABM serves for building Digital Twins of urban ecosystems at the level of individual trees and their future trajectories. Digital representation of trees can be created using a combination of datasets such as LiDAR, street view images, field surveys as well as qualitative description of typologies.

Machine Learning and statistical models are used to calibrate biomass growth patterns, carbon release schemes, immunity to contagions, etc.

In this paper, we analyze urban forests within the context of Glasgow. We examine various green area typologies and analyze how tree populations at each typology evolve over time. Health of tree populations and their contribution to ecosystem services are observed under various scenarios such as level of maintenance or different weather conditions. We report CO2 emissions, carbon sequestration, water retention capacity and avoided water runoff.

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Trees are a critical part of urban infrastructure, alongside bridges, roads and rail, enabling investment, profitability and sustainability. As a consequence of net-zero targets, cities around the world are pledging ambitious afforestation targets.

By 2030, Prague has pledged to plant one million trees (Dimitrova, 2021) while Sydney intends to add five million trees to the city’s existing urban forest (NSW Government, 2020).

However the realisation of such ambition is questionable given the current practices, tools and methodologies. They are generalistic and fall short at incorporating location specific context and hence craft effective and long term policies. This paper

The paper demonstrates replicability of SAF for policies and projects that aim for an economic case where benefits of urban forests far exceed its costs; making a compelling argument for maintaining a green infrastructure with carbon, water, health, energy, economic and social benefits serving as a basis for co-investments.

Pedestrian Level Green Infrastructure Survey.

Maider Llaguno-Munitxa, Marie Vander Meulen, Elena Agudo Sierra, Alejandro Burrgueno Diaz — UCLouvain_LAB green infrastructure — pedestrian view — green perception — urban comfort

The potential benefits of Urban Green Infrastructure (UGI) for the mitigation of the urban heat island effect, reduction of flooding risk, and improvements in the outdoor environmental quality are undeniable.

Thus, we should profit from the ongoing urban mobility transition and the increasing availability of urban land, to enhance urban health and wellbeing by demineralizing the urban cover. However, without a detailed survey of the pre-existing UGI characteristics, the potential socio-environmental and urban health benefits the implementation of new UGI could bring along may not be achieved.

Today, the UGI documentation methods deployed within urban planning processes generally rely on incomplete geospatial datasets – geo-localized tree catalogues, and green area polygons- that oftentimes only cover the public domain. Acknowledging the limitations of geospatial datasets, some municipalities and regions are starting to invest in initiatives to develop more detailed studies of the

tree canopy - this is the case for example with the Plan Canopee project launched by the city of Liege, or the i-Tree initiative developed by USDA Forest Service. However, relying on geospatial and aerial imagery has proved insufficient to develop a detailed characterization of UGI. Small scale UGI such as grass patches, bushes, green pots, or green walls are often ignored, and the three-dimensional structure, health condition, or the diversity of the urban forest are rarely documented. This research investigates a novel methodology to quantify UGI through the computation of the pedestrian level perception, combining geospatial, remote sensing and image processing technologies.

Focusing on 12 squares located in the municipalities of Saint-Gilles and Molenbeek within the Brussels Capital Region: i) satellite imagery from UrbISOrtho and Copernicus Sentinel-2 were compiled and using the Google Earth Engine, the Normalized difference Vegetation Index (NDVI) was computed, ii) geospatial data from UrbIS, BruGIS, Brussels Environment, and Mobility Brussels was analyzed 21 — for tree location and green area computations, and iii) 360° google-street view imagery was queried, and through semantic classification, the UGI types (trees, bushes & grass fields), their ratios, and their location was computed.

Our research methodology enables a comparison between aerial and pedestrian level quantification of UGI, and addresses the need for a high spatial resolution pedestrian level analysis, for the development of an accurate UGI documentation to implement in urban procurement processes.

Urban Greening Versus Urban Densification. Modelling four urban forest scenarios for 2050.

Agatha Czekajlo, Zhaohua Cheng, Sara Barron, Cynthia Girling, Lorien Nesbitt, Stephen Sheppard — University of British Columbia urban forestry — tree planting — canopy cover — future simulations — proxy models

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Urban forests are increasingly recognized as important tools in climate change mitigation and adaptation. Trees provide shade to buildings and outdoor spaces; sequester atmospheric carbon and other pollutants; assist with managing urban storm water; and provide many other health, social, and environmental benefits. Many cities are now setting tree canopy cover targets in their urban forest and climate action plans. For example, the City of Vancouver proposes to grow their total tree canopy cover to 30% by 2050 (City of Vancouver and Vancouver Park Board 2020).

Although there is strong support for planting trees to increase urban canopies, current gaps in knowledge include understanding relationships (especially conflicts) between urban greening and other climate actions, such as densification, and the feasibility of maximizing urban greening benefits while balancing these conflicting climate strategies.

Urban tree loss is common due to improper selection and/or care (Hilbert et al. 2018), and harsh site conditions – compounded by climate-related

stresses, such as increased drought severity (City of Vancouver and Vancouver Park Board 2018).

Therefore, it is critical for urban forest managers and sustainability practitioners to consider the interconnected relationships between urban forests, land use change, and climate change impacts and actions (Cheng et al. 2021). With limited assessment about how urban forest plans could interact with other climate action implementations, Canadian cities have “aspirational” tree canopy targets.

This work reports on a project that modelled four future what-if tree planting scenarios for increasing canopy cover and volume in a densifying neighbourhood in Vancouver, Canada. The 2020 canopy cover for this neighbourhood was reported as very low (< 10%), which prompted the question: Is it possible for such a neighbourhood, which is expected to increase its population density by 33%, to achieve 30% canopy cover by 2050? We used spatial proxy models to create and assess urban form and forest changes between baseline (2020) and future scenarios (2050). Freely available LiDAR, field-based inventory, and open-source tree characteristics data provided information about baseline and future “planted” trees. The four future scenarios were based on evidence-driven tree planting strategies, which characterize: maintaining existing municipal urban forestry policies with and without climate-adapted tree species; strategically planting trees to reduce building energy, and; maximizing tree planting across the neighbourhood. Based on mortality assumptions, between 1,853 and 2,445 trees aged out since 2020 and were all replaced following species and size rules specific to each scenario. We also “planted” between 6,079 and 11,726 new trees across the four scenarios, totaling 10,228-15,823 trees. Canopy cover increased from 7% in 2020 to a maximum of 16% by 2050. Even with our maximize tree planting scenario we were unable to achieve 30% canopy cover at the neighbourhood scale.

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The Impact of Urban Greenspaces on Heat-related Mortality in Elderly. A realist synthesis.

Tom Cornu — Global Health Science, KU leuven climate change — urban heat islands — urban green space — heat-related mortality — realist synthesis

One of the most certain and direct consequences of climate change on urban health is heat-related morbidity and mortality due to heatwaves, aggravated by the urban heat island effect. Vulnerable groups, especially elderly, will be the most affected.

A solution put forward in many national and international reports and policy documents is the introduction or expansion of urban greenspaces.

While urban greenspaces have a proven effect in decreasing the ambient temperature and reducing heat related mortality, the studies establishing the correlation are mostly observational and causal pathways are far from clear. The causal effect of heat on mortality is complex asheat often increases pre-existing symptoms and aggravates chronic disease. Moreover, results vary for different contexts, population types and characteristics of greenspaces as urban greenspaces are ‘complex systems thrusted into complex systems’. Different studies mention factors influencing the impact of greenspaces, some

describe possible pathways for different health aspects. But to our knowledge there is no systematic synthesis of the literature to examine the mechanisms by which and the circumstances under which green spaces work to decrease heat related mortality for elderly.

Methodology — We used a theory-driven review method –realist synthesis– to develop a complexityand context-sensitive program theory. As a first step, starting from reports from international and supranational organisations and institutions like WHO, World bank, IPCC and the European Commission a causal loop diagram was constructed which describes the possible pathways throughwhich urban greenspaces influence heatrelated mortality in elderly. In a second step, one of the pathways -how urban greenspaces may lead to a reduction of heat-related mortality by increasing social capital– as well as its links with other pathways is further exploredfor underlying mechanisms, the context in which they work and the differentiated patterns of outcomes they 23 — generate. Literature is searched for evidence supporting or contradicting the initial program theory, resulting in a refined theory.

Results — Results show how urban greenspace can impact heat-related mortality in elderly by its influence on their exposure to outdoor and indoor heat, by improving their resilience to heatwaves as well as by affecting their access to treatment. Urban greenspacesand its interactions with social capital affect the access to health information, social support,and the capacity for effective lobbying. Several mechanisms help to explain these observed demi-regularities, among others perceived behavioural control, perceived usefulness, receptiveness, ontological security and self-interest. If and how they are triggered depends on the characteristics of the urban greenspace, the population and other contextual factors.

NOTES —

SCIENCE SESSION I I CLIMATE SMART URBAN FORESTS: WHAT & HOW?

— Moderation: BEN SOMERS Earth and Environmental Sciences, KU Leuven SASKIA DE WIT How Trees Shape Urban Spaces.

FANNY MAURE SylvCiT.

KAREN DE PAUW The Urban Heat Island Accelerates Litter Decomposition Through Microclimatic Warming in Temperate Urban Forests.

SONIA LE MENTEC Bibliometric Analysis to Identify Thematic Crossreferencing of Studies on Urban Heat Island and Greening at the Urban Canopy Scale.

RITA SOUSA-SILVA Which Trees Can Withstand Climate Change and Other Urban Stressors?

The value of urban forests for heat alleviation, air filtering, carbon sequestration, and water regulation is widely acknowledged. Yet, due to climate change urban forests are under increasing pressure. The harsh environmental conditions prevent them to achieve its full ecosystem service provisioning potential. New insights in monitoring, management and design are needed to make our urban forests more climate-smart/resilient.

ANNALISA METTA Timing for Urban Forestry.

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How Trees Shape Urban Spaces.

Elaborating the multiplicity and spatial differentiation of the urban forest from an urban tree configurations perspective.

Saskia de Wit — Landscape Architecture, Delft University of Technology tree vocabulary — Delft — tree configurations — spatial perception — site specificity

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How can mapping be used to understand and communicate the spatial-experiential characteristics of the urban forest? Because the expansion of the urban forest will take place in and around existing cities, knowledge of the existing ‘tree language’ of these cities is indispensable: ordering, naming and showing essential characteristics of different tree structures. To unravel the tree language of cities, this paper explores the ‘vocabulary’: the components of this language, using the city of Delft as a case study.

Tree vocabulary refers to the spatial relationship between tree species, planting configurations and tree structures, and their specific location.

Field research, historical documentation and cartographic research resulted in a spatial typology for the urban forest from a landscape architecturalphenomenological point of view: trees create space, and their perceivable form (structure, proportions, texture) is relevant insofar as it determines the surrounding space in which people can move and act, which means that they are defined in relation to the human body. How trees define space can be understood from the characteristics of the trees itself, of the tree configurations, and of wooded areas, as three different ‘legends’ to read the map of Delft as a wooded city from different angles. By mapping the city in this way, the inner city and the suburban recreational area can be read as not equal but equivalent components of the urban forest mosaic.

In this paper the focus is on the typology of tree configurations: the shape of the surrounding, threedimensional space, as determined by the relative disposition of the trees (and shrubs), and their crown relative to the trunk as the components of the shape. When several trees are planted together, the spatiality is determined by the joint configuration and no longer by the individual tree form (just as in a natural forest the individual tree form disappears in favor of the forest as a whole).

The volume of the trees is complementary to, and determines, the surrounding space. An ensemble of different configurations in the post-war urban area Verzetstrijdersbuurt is used to showcase how the relations between different configurations defines the Delft urban forest.

This approach has two specific benefits: it highlights the connections as well as the site-specific qualities of the existing urban forest components. If these aspects are considered in management and expansion of the urban forest, they can be a tool for creating stronger relations between the different components, as well as diversity and heterogeneity in urban forests.

SylvCiT. A new intelligent tool to improve urban forest resilience to global changes.

Fanny Maure (2/3), Annick St-Denis(1/2), Raouf Belbahar(2), Sylvain Delagrange(1), Marie-Jean Meurs(2), Christian Messier(1/2/3) — (1) Universite de Quebec en Outaouais (ISFORT, CEF), (2) Habitat, Montreal QC, (3) Université du Québec à Montréal

to guide UF managers in their planning of tree plantation. Based on inventories of georeferenced urban trees, the tool analyses species diversity, functional diversity and forest structure at different scales (city, neighborhood, park, street). SylvCiT then provides recommendations on a selection of tree species to plant to increase the functional diversity of the UF.These suggestions will also take into consideration the tree species’ vulnerability to biotic and abiotic threats (e.g. insects, pathogens, drought, flood, ice storms, wind storms). Future climate conditions will soon be included to further guide species recommendations.

functional diversity — intelligent tool — urban forest management — tree plantation

– The Urban Heat Island Accelerates Litter Decomposition Through Microclimatic Warming in Temperate Urban Forests.

Karen De Pauw (1), Leen Depauw (1), Sara AO

Urban trees are facing and will continue to face many challenges in the next decades such as climate change, and the invasion of new pest and pathogens, which can have severe consequences particularly in low diversity urban forests (UF).

Indeed, most UF of northeastern North America are dominated by only a few species. For example, in Montreal, Laval and Quebec cities(Canada), two genera are dominant: Acer and Fraxinus.There is an urgent need to improve the resilience of UF to global changes by increasing the functional diversity of the canopy with strategic selection of tree species for plantation. Tree species with different traits will have different responses to threats and stresses. A resilient UF will maintain the production of ecosystem services despite the arrival of a new insect or exotic disease, a drought, a frost event or other stress event.In collaboration with students in computerscience, the aim of our project is to develop a new intelligent tool, SylvCiT,

Cousins (2), Emiel De Lombaerde (1), Martin Diekmann (3), David Frey (4, 5), Katarzyna Kwietniowska (6), Jonathan Lenoir (7), Camille Meeussen (1), Anna Orczewska (8), Jan Plue (9), Fabien Spicher(7), Thomas Vanneste (1), Florian Zellweger (10), Kris Verheyen (1), Pieter Vangansbeke (1), Pieter De Frenne (1) — (1) Forest & Nature Lab, Department of Environment, Faculty of Bioscience Engineering, Ghent University, (2) Landscapes, Environment and Geomatics, Department of Physical Geography, Stockholm University, (3) Vegetation Ecology and Conservation Biology, Institute of Ecology, FB2, University of Bremen, (4) Research Institute of Organic Agriculture (FiBL), Department of Socioeconomic Sciences, (5) Franklin University Switzerland, Division of Environment, Mathematics, Psychology, and Health, (6) ul. Wincentego Kadłubka 6c/12,

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(7) UR “Ecologie et Dynamique des Systèmes Anthropisés” (EDYSAN, UMR 7058 CNRSUPJV), Jules Verne University of Picardie, (8) Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia, (9) IVL, Swedish Environmental Institute, (10) Swiss Federal Research Institute for Forest, Snow and Landscape Research WSL, Birmensdorf 8903, Switzerland forest edge — litter decomposition — microclimate — soil moisture — teabag

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Forests worldwide are experiencing high levels of fragmentation, with especially important consequences for ecosystems bordering urbanized areas. The urban heat island associated with builtup area enhances local warming and affects urban forest biodiversity and ecosystem functioning. In forests, litter decomposition is a key ecosystem function affecting carbon and nutrient cycling.

This process is driven by the local microclimate (temperature and soil moisture) but the impact of the urban heat island on litter decomposition in urban forests remains largely unclear.

Here we studied soil microclimate and litter decomposition in six urban forests across Europe and along local gradients from the urban forest edge to the forest interior. To unequivocally quantify decomposition independent from local forest composition and litter quality, we used standardized green tea and rooibos tea litterbags. We then assessed the effects of built-up area and forest area in the surroundings on the soil

microclimate for different spatial scales. Secondly, we determined the role of the soil microclimate and other environmental drivers for litter decomposition. Soil characteristics and the litter quality of the present tree and shrub layer were only driving green tea and not rooibos tea decomposition.

On the contrary, soil temperature was an important driver of decomposition for both tea types. Higher soil temperatures resulted in faster rates of litter decomposition and were related to the proportion of built-up area in the landscape. Via structural equation modelling we detected cascading effects of the urban heat island on litter decomposition. Such changes in litter decomposition due to urban heat have the potential to alter the soil food web, nutrient cycling and carbon drawdown in urban forests, and cause significant interactions between urbanisation and ongoing climate change.

– Bibliometric Analysis to Identify Thematic Cross-referencing of Studies on Urban Heat Island and Greening at the Urban Canopy Scale.

Sonia Le Mentec (1), Maria Ernst (1), Benjamin Loubet (1), Erwan Personne (1), Patrick Stella (2) — (1) Université Paris-Saclay, INRAE, AgroParisTech, UMR ECOSYS, (2) Université ParisSaclay, INRAE, AgroParisTech, UMR SADAPT bibliometric analysis — vegetalization — atmospheric pollution — urban heat island — microclimate

The artificialization of surfaces within cities leads to an increase in temperatures in the neighbourhoods compared to the surrounding areas. The urban

du Québec à Montréal (UQAM), Montreal, QC, Canada, (3) Institut des Sciences de la Forêt Tempérée (ISFORT), Université du Québec en Outaouais (UQO), Ripon, QC, Canada tree management — urban forestry — stress tolerance — expert knowledge

heat island (UHI) is a well-known phenomenon at the city scale and this study focuses on the urban canopy layer which occurs at the pedestrian level and therefore affects the citizen comfort. A bibliometric study is performed in order to describe and understand the links with urban greeninginduced modification of the urban canopy layer, air quality and microclimate. Science mapping of bibliographical resources that were extracted from the Web of Science Core Collection database is used.

A number of dominant themes related to our topic were selected in order to highlight the connections existing between them, within the field of the UHI research. For example, we found that the effects of vegetation on microclimate and air quality are treated independently but not in a coupled manner.

More generally, we found that coupled effects are poorly addressed in the literature.

– Which Trees Can Withstand Climate Change and Other Urban Stressors? Using the Delphi technique to build consensus in practice.

Rita Sousa-Silva (1), Maribel Aristizabal (2), Jérôme Dupras (3), Christian Messier (2,3) — (1) Young Academy for Sustainability Research (YAS), Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Germany, (2) Centre for Forest Research (CEF), Université

As the climate continues to warm and the world becomes progressively more urbanized, our reliance on trees and the ecosystem services they provide is 29 — rapidly increasing. Worldwide, cities are resorting to planting trees to offset rising temperatures, trap pollutants, mitigate climate change, and improve human health and well-being. However, urban areas are a challenging environment for trees to grow.

They must cope with compact spaces, air pollution, elevated summer temperatures, reduced water availability, and less-than-perfect surroundings.

Hence to optimize the survival and growth of trees planted in cities, understanding the vulnerability of tree species to multiple stressors is essential, as responses to stressors are very different from one species to another. Furthermore, urban foresters regularly rely on certain species, which is cause for concern since species may not be suited to the climate of the future. Therefore, species diversity is key to increasing the resilience of the urban forest to future abiotic and biotic stresses. However, current knowledge on tree vulnerabilities to climate change and other urban stressors remains scarce and available only for a limited number of tree species

and/or specific stressors.

Focusing on the most abundant urban tree species in northeastern North America, in our study, we sought to classify tree species according to their tolerance to multiple stressors and disturbances— soil compaction, air pollution, insects and diseases, ice storms, snow, de-icing salts, strong winds, drought, and extreme temperatures—as well as to assess which intrinsic characteristics may capture a species’ ability to cope with these stressors. To do so, in the first part of our study, we used the Delphi method to elicit the knowledge of experts (here, urban forestry professionals). The Delphi is a group facilitation technique that seeks to obtain consensus on the opinions of experts through a series of structured questionnaires in situations where there is contradictory or insufficient information, as is the case for species-specific sensitivity and tolerance to stress. Then, in the second part of our study, we circulated a questionnaire through networks of students and professionals in forestry to gain access to more people in the field and a wider range of — 30 opinions.

Among the most abundant urban tree species in northeastern North America, Ginkgo biloba, Gleditsia triacanthos, and Quercus and Ulmus spp. were rated by the experts as the most tolerant to the studied stressors, although none of the species were rated as tolerant to all stresses and disturbances.

Furthermore, there was a lack of agreement among respondents regarding the degree to which a given species was likely to be affected by (or respond to) a given stressor. This has also allowed us to highlight gaps in knowledge that require further study.

These findings fill important gaps in our knowledge of trees’ vulnerabilities and thus may be useful in informing the choice of tree species that could be planted across our cities (e.g., reducing the costs of tree maintenance and replanting) to build the resilient urban forests the 21st century needs.

Timing for Urban Forestry.

Annalisa Metta — Architecture Department, Roma Tre University polycyclic plantation — time-oriented design — self-reliant morphogenetic process

In a relentlessly urbanized planet, when climate change and environmental alterations are increasingly and sometimes irreparably serious, urban forests are claimed as superheroes capable of saving cities from their lethal destiny. Intended as service-providers for enhancing biodiversity, improving environmental indicators, and ensuring ecological sustainability, urban forests are asked to guarantee measurable and assessable results, achieve top-of-the-heap scores according to the performance tables of ecological functionalism, as if they were tried-and-tested devices or ready-made facilities, able to supply immediate, stable, and reliable effects.

Yet, forestation is never an instantaneous action, and it does not produce constant results. It is rather a ceaseless ongoing process. Therefore, putting urban forestry into a medium-long term horizon is an inescapable and constitutive projection for any design, which is fatally called to collaborate with both the biological rhythms of the living beings and the socio-economical rhythms of the urban metabolism. So, time-variable is crucial when listing the data proving the profitable services given by planting forests into the city, because the quantities

of the captured pollutants or the reduction of the heat island critically depend on the age of the trees’ population (growing and expiry) as well as on their seasonal features (recurring cycles). Likewise, time affects the architecture of the urban forests, in terms of density, sameness, or diversity of the planting patterns, both driven by sylvicultural practices and by the forests’ self-reliant morphogenesis, such as self-thinning as a strategy of survival and regeneration. And the two issues – urban forests as trees architecture and urban forests as ecological infrastructures – should never be divorced. Already in 1827, in his Traité général des eaux et forêts, chasses et pêches, Jacques-Joseph Baudrillart underlines the advantages coming from what we today name ‘polycyclic plantation’: in the board titled ‘Projet d’avenues perpetuelles’, he proposes to plant uneven-aged trees of different species and to remove some trees every few decades, to keep the alignment (architecture) and provide wood resource (sustainability). More recently, projects conceived by well-known landscape architects – from Michel Desvigne to Studio Vulkan, from LOLA to TK Studio − highlight some possible applications of timing for urban forestry; for instance, some of them start with dense, obsessive plantings and then make room through subtraction and thinning; other ones operate in the opposite way, pushing the progressive thickening of the trees.

Assuming time as a design tool for urban forestry is challenging because it requires to deal with variable settings and even a certain degree of unpredictability: it asks for accepting that the outcomes, both in terms of space and ecology, are always provisional and linked to contingencies that cannot always be foreseen. This spoils the very idea of efficiency and guarantee of performance typical of ecological and economical determinism. Timing for urban forestry precisely asks for overcoming the idea of urban forests as appliances, such as machines or gadgets, because they continuously change, develop, get stronger as well as vulnerable, they age and perish, according with the laws which rule the biological and social life of both trees and humans.

HEAT PLAN & GREENING POLICY OF LEUVEN David Dessers — Deputy Mayor in Leuven

Dessers studied journalism at the Katholieke Hogeschool Mechelen.Before becoming deputy mayor, he was known for his climate activism and engagement in the North South movement. He worked for NGO’s like Oxfam and 11.11.11. He subsequently co-founded Climaxi, a climate organisation. From 2011 to 2018 he organised a yearly solidarity festival in Leuven called Wereldfeest. He has a very broad social engagement. He was co-founder of the Centre for Economic Disobedience (CEO) and is a founding member of Leuven2030. Apart from that he (co)-wrote several books, one published in 2017 titled ‘Leuven in alle straten. Voor een stad die durft’.

Dessers was first elected as city councillor in 2012. Since January 1st, 2019 he is deputy mayor for mobility, climate and sustainability, agriculture and food.

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COLOPHON CO-CHAIRS CHIARA CAVALIERI LAB, UCLouvain

ORGANIZING COMMITTEE

CECIL KONIJNENDIJK Francqui Chair 2022

LAURA CALDERS Department of Architecture, KULeuven

KELLY SHANNON Department of Architecture, KULeuven

CHIARA CAVALIERI LAB, UCLouvain

SCIENTIFIC COMMITTEE PHILIPPE BARET Earth and Life Institute, UCLouvain FRANCESC BARÓ Department of Geography, VUB NADIA CASABELLA Faculty of Architecture, ULB MICHIEL DEHAENE Department of Architecture, UGent BRUNO DE MEULDER Department of Architecture, KULeuven HANS LEINFELDER Department of Architecture, KULeuven CHRISTIAN MESSIER Francqui Chair 2021-22 BART MUYS Earth and Environmental Sciences, KULeuven BRUNO NOTTEBOOM Department of Architecture, KULeuven BEN SOMERS Earth and Environmental Sciences, KULeuven MAARTEN VAN ACKER Faculty of Design Sciences, UAntwerpen CAROLINE VINCKE Earth and Life Institute, UCLouvain

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BRUNO DE MEULDER Department of Architecture, KULeuven KHALDA EL JACK Department of Architecture, KULeuven KRISTEL MAZY Faculty of Architecture & Urbanism, UMons LISA NEDOSSÉKINA Department of Architecture, KULeuven CECIL KONIJNENDIJK Francqui Chair 2022 KELLY SHANNON Department of Architecture, KULeuven — GRAPHIC DESIGN / WEBSITE Valerian A. Portokalis & Xenia Stoumpou

The International Center of Urbanism (ICoU) focuses on the most pressing contemporary issues at stake in settlements and environments across the globe. Urbanization continues to gallop ahead in most parts of the world, while massive restructuring is clearly necessary in post-industrial societies. At the same time, business as usual is challenged by unprecedented migration of humans and species and the consequences of climate change.

IN COLLABORATION WITH: — KU LEUVEN

— UC LOUVAIN

WITH SUPPORT OF:

ISBN — 978-9-46444-723-1 — 1 / 3