Rob Mac Kenzie The influence of urban form

Rob Mac. Kenzie: The influence of urban form and urban trees on air quality: current patterns and systems-thinking for change http: //www. birmingham. ac. uk/research/impact/policy-commissions/future-urban-living/index. aspx

Air pollution Ozone (O 3) – spreads over city-region Nitrogen dioxide (NO 2) & Nitric Oxide (NO) Microscopic Particulate Matter (PM 10, PM 2. 5, nano-particles) Volatile Organic Compounds (VOCs) Pictures from M. Z. Jacobson, Atmospheric Pollution. Left: Pedestrians in the 1950 s, Hollywood Citizens News Collection, Los Angeles Public Library. Right: Los Angeles on 23 July 2000, Jacobson.

Urban form I The built land surface can affect air pollutants in five ways: 1. Site for creativity → resource use and waste (urbanisation) 2. Trapping pollutants in the spaces between buildings (fumigation) 3. Producing swirls and eddies in the air that mix pollutants away from the ground (ventilation) 4. Slowing the horizontal wind → reducing horizontal dilution 5. Transfer of pollutants from the air to the surface (deposition)

Urban form II Green Infrastructure can amplify built environment effects (except urbanisation) and produce two additional effects: 1. Emitting volatile organic compounds (VOCs) that form ozone 2. Making space for cleaner air No single model captures all these effects, but models can show us examples of when each effect is likely to dominate…

Trees, green walls, and street-level air quality With Tom Pugh, Nick Hewitt , and the Urban Futures team With Irina Nikolova, Roy Harrison, and the FASTER team

Effect of urban built form C = f( E, M, D) How do fumigation, ventilation, and deposition interact?

In-canyon concentration reduction (%) Green walls can be much more effective than green roofs…(central London example) Shallow canyon Deep canyon …and can clean air in a single canyon (localism). Bottom-up policy becomes possible. Political traction. Pugh, T. A. M. , A. R. Mac. Kenzie, et al. (2012). The effectiveness of green infrastructure for improvement of air quality in urban street canyons. Environmental Science & Technology, 46 (14), 7692 -7699. DOI: 10. 1021/es 300826 w

NERC URGENT programme (2001) http: //www. es. lancs. ac. uk/people/cnh/Urban. Trees. Brochure. pdf Trees & Design Action Group (2012): http: //www. tdag. org. uk/trees-in-the-townscape. html Practitioner tools for urban forestry for air quality enhancement Woodland Trust (2012): http: //www. woodlandtrust. presscentre. com/Media. Library/Urban-Air-Quality-774. aspx - revision forthcoming in 2015

How large-scale urban structure affects pollution emissions With Matt Barnes, Duncan Whyatt, Nick Hewitt Barnes, M. , Ph. D Thesis, Lancaster University, 2014.

Scaling (allometric) analysis of 360 US cities = 1. 15 1: economies of scale = 1: proportionality > 1: increasing returns for scale Luis Bettencourt & Geoffrey West (2010) A unified theory of urban living, Nature 467, 912– 91

Scaling analysis of 4837 UK settlements n = 4837; r 2 = 0. 71 = 0. 91 Scale-invariant form & function Variability in the form and function of settlements 100 1, 000, 000 Barnes, M. , Ph. D Thesis, 2014. Modest “economy of scale” when considering all UK settlements

Current situation We should never expect all settlements to have the same pollutant concentrations (even without point sources) because: 1. Settlement area will vary positively with population 2. Settlement emissions will vary positively with population “pure luck” 3. Concentration scaling will depend on the difference of the emissions scaling and the (square-root-of-area) scaling 4. Balance between emissions and advection Target should be for concentrations to reduce with population! Emissions control

Sustainability and Interventions I Sustainability, no matter what definition is used, is all about the future - putting in place now interventions (solutions) to problems that will yield a positive rather than negative future legacy. The essential underlying question is: “how sustainable are these interventions? ”, while the answer inevitably is: “it depends on how the future develops”.

The Future is plural Futures thinking exploits the human capacity for change Urban Futures are • derived from established philosophical positions: Hobbes, JS Mill, Adam Smith, Schumacher. • derived from global scenarios → consistency across scales Derived urban futures can pressure-test sustainability solutions Method gives rise to a shared rationale for interventions can guide practice at every level from policy formulation through to implementation in specific sites, reducing the risk of “box-ticking”. Boyko, … Mac. Kenzie et al. , Benchmarking sustainability in cities: The role of indicators and future scenarios, Global Environmental Change, 22(1), 245 -254, doi: 10. 1016/j. gloenvcha. 2011. 10. 004, 2012. Hunt, … A. R. Mac. Kenzie, et al. , Scenario archetypes: Converging rather than diverging themes, Sustainability 2012, 4(4), 740 -772; doi: 10. 3390/su 4040740

Sustainability and Interventions II An intervention must have an intended benefit, but it is often lost in the design or decision chains of planning and development. Any intervention can have unintended drawbacks. Drawbacks are often context-specific, but so too are benefits. Mac. Kenzie, A. R. , T. A. M. Pugh and C. D. F. Rogers, “Sustainable Cities: seeing past the trees”, Nature, 468, p 765, 9 December 2010.

Resilient design puts in place necessary conditions and avoids hostages to fortune

STEP 5 a Implement INNOVATION STEP 1 STEP 2 STEP 3 STEP 4 STEP 5 b Solution & Benefit Necessary Conditions Future Performance Resilience to future change Adapt STEP 5 c Seek Alternative

STEP 5 a Implement INNOVATION STEP 1 STEP 2 STEP 3 STEP 4 STEP 5 b Solution & Benefit Necessary Conditions Future Performance Resilience to future change Adapt STEP 5 c The analysis has flagged up reasons why the solution may fail. This is the starting point for adapting the solution or. . Seek Alternative

STEP 5 a Implement INNOVATION STEP 1 STEP 2 STEP 3 STEP 4 STEP 5 b Solution & Benefit Necessary Conditions Future Performance Resilience to future change Adapt STEP 5 c This analysis - reasons why the solution may fail. Starting point for adapting the solution or. . Considering more resilient alternatives INNOVATION Seek Alternative

“Systems thinking” for something as complicated as a city can feel like running an n-dimensional 3 -legged race… Source: tiswango flickr. com/tiswango

wisdom Evidence-based deduction; vision; ideology One-world living Vanguardism Leadership New ways of living; New ways of making a living New structures for living; New ethical codes for making a living Over-reaching expertise Change in hearts and minds; Niche creation Moral pressure for change in rules NARRATIVE Ecosystems Communities The Market Consumptionbased demand Emergence Regulations Business models Planning Consumptionfocused metrics Design Resource consumption

One-world living Vanguardism Leadership Best when ? ? Strongest when value/values are explicit Strongest when costs are internalised Ecosystems Communities The Market Best when trusted Emergence Strongest when vision is embedded in a narrative Strongest when experiments are encouraged Regulations Business models Planning Best when agile Design Resource consumption

Thank you bifor@contacts. bham. ac. uk @BIFo. RUo. B www. birmingham. ac. uk/bifor http: //www. birmingham. ac. uk/research/impact/policy-commissions/future-urban-living/index. aspx