Dr Kieron Doick. Forest Research

Transcription

1 Dr Kieron Doick Forest Research

2 Keeping London a Cool Place to be: the role of greenspace Dr Kieron J. Doick Acting Head Land Regeneration and Urban Greenspace Research Group and co-authors Tony R. Hutchings and Vicki Lawrence

3 Scene setting Land Regeneration Urban Greenspace Ecosystem service provision urban trees and greenspaces Quantification and valuation Decision making Ecosystem services Provisioning Regulating Supporting Cultural Climate regulation (heat abatement) 3

4 Keeping London a cool place to be - Introduction - Methodology - Results - Implications - Future work 4

5 Introduction The Urban Heat Island (UHI) higher mean average temperature in cities than surrounding countryside UHI = Temp (Urban) - Temp (Rural) First reported by Luke Howard in 1820 Ref: GLA (2006) London's urban heat island: A summary for decision makers 5

6 Introduction (cont.) Nice and warm, so why the fuss UHI intensity can be as much as 7 o C and is increasing There is a direct and significant impact of heat on human health ~ 1,100 heat-related deaths and 100,000 hospital patient-days per year in the UK plus 10s to 100s more deaths per heat wave 30 th June to 2 nd July 2009 = 299 excess deaths in England Climate change scenarios are for rural setting Multiple cooling mechanisms offered by vegetation, additive and significant at city scale Transpiration > Reflection of solar radiation > Shading 6

7 Methodology T4 T3 T2 G3 & G4 G1 & G2 T1 Key: G = grass T = tree 7

8 Methodology (cont.) Sensor locations along street transects N 800 m H F Queensway 400 m I D E C Gloucester Terrace B J G K L 200 m A 100 m Kensington Gardens Key: South: A, B, C, D, E, F Trees: A, E, G, I North: G, H, I, J, K, L Lamp posts: B, C, D, F, H, J, K, L Intersections: A, F, H, L 8

9 Methodology (cont.) 9

10 Air Temperature, o C Results Comparison of air temperatures at four locations within Gloucester Terrace (one 24 hour period) Intersection Time, hours Lamp post Street trees 10

11 Results Streets significantly warmer than the average temperature across Kensington Gardens, and Queensway warmer than Gloucester Terrace Street canyons not significantly warmer than intersections (high variability at intersections) Significant difference in air temperatures on north and south side of street not observed Grassed area of Kensington Gardens significantly warmer than the tree-lined area in August and September (ANOVA, p<0.05) 11

12 Heat Island Intensity, Variation in heat island intensity at mid-point along Gloucester Terrace transect (August) Results 8 o C Time of day (hour) 12

13 % time % time % time % time Frequency Distribution plots Gloucester Terrace A Day time C Kensington Gardens B o Heat Island Intensity, KC Night time D o Heat Island Intensity, KC Heat Island Intensity, o KC Heat Island Intensity, o KC 13

14 Analysis of heat island intensity at various locations across London Max and Min s are the largest and smallest hourly UHI value observed in a month Mean values are for the month Results Location Heat Island Intensity ( o C) August September October Max Mean Min Max Mean Min Max Mean Min St James Kensington Gardens Gloucester Terrace Queensway

15 Heat Island Intensity ( Results Temperature gain with increased distance from Kensington Gardens 3.5 Heat Island Intensity ( A B 4.5 o C) 3.0 o C) Distance (m) Distance (m) A) 10 th August B) 28 th September 15

16 Implications Urban dwellers are exposed to warmer temperatures for longer periods than people living in the countryside It is cooler close to a large greenspace than [say] m away; street trees offer some protection too (limited focus of this study) Impact of cooling by large greenspaces may be highest when needed the most Dormancy and frosting of urban trees/green spaces is less than in countryside & decreasing Forecasted new climate for UK will increase pressures on urban greenspaces: socially and environmentally 16

17 Future Work More questions Impact of on cooling effect greenspace size greenspace design (relative proportions of hard surfaces, grass and trees) Cooling boundary: what governs Shape Size Permanence Penetration into surrounding areas (role of street canyons vs. buildings as barriers to air movement) 17

18 Future Work Cooling by vegetation vs. thermal comfort Valuing the cooling effect of street trees green spaces green infrastructure Species selection for optimised cooling How to position street trees for optimal cooling 18

19 The end My thanks to The Royal Parks, the Royal Borough of Kensington and Chelsea, and the City of Westminster for permissions Ros Bryant, Vicki Lawrence and Andy Brunt for all their contributions to the project Andrew Peace, Paul Taylor and Paul Henshall for help with statistics and data processing The Forestry Commission for funding 19