From ecology in urbanism to ecology of urbanism

楊沛儒 美國喬治亞理工學院建築學院城市區域規劃及建築學副教授

Perry P. J. Yang Associate Professor of City & Regional Planning and Architecture

第二自然與第三生態The second nature and the third ecology

生態城市主義：五種論點及設計方法- Ecological urbanism: 5 propositions

設計案例- Projects of Eco Systems Design Studio (ESD)

Global metropolitan sprawl, mega urban form, new urban world

Ecological effects of mega city-regionUrban sprawl and rapid urbanizationEcological footprints go beyond geographic boundary

Source: Yale Global Online, 2007

Pearl River Delta

Tokyo Bay

Yangtz River Delta

Seoul City-RegionBeijing-Tianjin City-Region

the second nature

Taipei-Hsinchu economic region

spatial patterns produced by urban and natural processesAtlanta and Shanghai

Shanghai Lujiazui CBD

Atlanta downtown

1KM

Richard Forman, 2002

The Third Ecology Proposition – the third facet in urban sustainability

3. Ecosystems Compatibility in Flow & Form

--the articulation of form and flow of urban, industrial and natural system

2. Ecological Efficiency

To optimize input-output ratio, dematerialization by technological

innovation and a new way of environmental management.

1. Social Sufficiency

An approach that responds to the “limits to growth” by self limitation of

needs and consumption

A few new questions for an ecology of urbanization

- How do we nurture bio-diversity in urban environments?

- Can ecology drive new spatial forms and temporal dynamics for reconstructing ecological networks, material flows and the new relationship between humanity and nature?

- What are the social and cultural implications of the ecology-driven landscape?

Conceptual diagram of Guangzhou city-regional strategy , Guangzhou White Swan Urban Design CompetitionPerry Yang Studio, 2008

ecological urbanism: 5 sets of keywords

- form. geometry. topography

- perception. sensuous quality

- surface. materiality. land mosaics

- scale. system. complexity

- stochastic process. temporal dimension

5 questions to ecological urbanism

1.Form. geometry. topographywhat urban forms perform better ecologically?

2. Perception. sensuous qualityEcological effect is a subjective matter and it varies according to the position of perceiver or receiver 3. Surface, materiality, land mosaicsHow do we track ecological flows across urban material surface and land mosaics, and then plan for symbiotic relationship?

4. Scale, System and Complexityhow do we articulate multiple patterns across different spatial scales that can be observed in physical environment? What are their cross-scale relationships?

5. Stochastic process and time strategyhow do we move urban change toward sustainability?

Atlanta: a hybrid landscape

1.

- form. geometry. Topography

what urban forms perform better ecologically?

- perception. sensuous quality

- surface. materiality. land mosaics, performance

- scale. system. complexity

- process. temporal dimension

the grid as generator(Urban Space and Structures, Martin & Marsh, 1972)

Savannah Manhattan

no control super blockEcocity in China, SWECO, 2008

urban form indices3D (Urban Space and Structures, Martin & Marsh, 1972)

Variation of a single building - A: tallest & smallest building coverage (bc)

Daylight exposure (SVF): from bc=100% to bc=10%

Relationship of density, typology and environmental performance

A

Building Coverage

Bui

ldin

g H

eigh

t

Martin & March (1972)

- form. geometry. Topography

2. - perception. sensuous quality

Ecological effect is a subjective matter and it varies according to the position of perceiver

- surface. materiality. land mosaics, performance

- scale. system. complexity

- process. temporal dimension

Viewshed analysisKevin Lynch, Managing the Sense of a Region, 1976

Viewsphere: A proposition of 3D visual analysis

YANG, P P J, Putra S Y and Li W, 2007, Viewsphere: GIS-based 3D visibility analysis for urban design evaluation, in Environment and Planning B: Planning and Design, Vol. 27. 971-992.

( )ij

i

HSvolumeVoS

DCBABVSI =

+++=

HemisphereHSi0

A

BD

C

VoSij

Sky

C & D invisible

visible

QijObstruction

Origin (Vantage)Oi

TargetTij

Interpolated raster mapping

3D visibility analysis on Singapore downtown

high-riseopenness

medium-rise(mass housing)

low-rise,compactness(traditional

settlement)

Solar Availability and daylighting :measuring ‘Sky view factor’ of typologies

VSI + SVF = 1ASVF

A B=

+

-form. geometry. topography

-perception, sensuous quality

3.- surface. materiality. land mosaics

How do we track ecological flows across urban material surface and land mosaics, and then plan for a symbiotic relationship?

- process. temporal dimension

- scale. system. complexity

Tracking Sustainable Urban Forms and Material Flows in Singapore

Yang, P P J, 2008, book chapter in World Cities and Urban Form: Fragmented, Polycentric, Sustainable? Routledge.

Conversion from dense and light vegetation to urban land cover

Change 1986 – 1994Change 1994 – 2002

Urban expansion

Change 1986 – 1994Change 1994 – 2002

Conversion from dense vegetation to light vegetation in some locations

Deforestation

Change 1986 – 1994Change 1994 – 2002 Change 1986 – 1994

Change 1994 – 2002

Conversion from light vegetation to dense vegetation in other locations

From urban land cover to dense and light vegetation

Reforestation Rezoning

LANDSAT ETM 2002SPOT image 1994SPOT image 1986

Landscape Ecological Analysis of Singapore’s land cover change

LAND COVER DATA DATA % DATA DATA % DATA DATA %

1986 1986 1994 1994 2002 2002

Dense Vegetation 74.405 13.38 55.469 8.12 111.4 16.50

Light Vegetation 76.788 13.81 122.04 17.87 92.872 13.76

Urban 337.12 60.64 429.05 62.84 430.35 63.74

No Data 67.613 12.16 76.225 11.16 40.516 6.00

TOTAL 555.93 100.00 682.78 100.00 675.14 100.00

Table: Sum of Patch Area (sqm)

• Landscape ecological indices to measure land cover patterns.– Greener: Increasing green area over 16 years of urban development, – Landscape fragmentation: More smaller-size green patches as well as smaller-size &

scattered urban development. – City form more compact : Urban form is more compact and less convoluted

Steel Stock Change Cement Stock Change

Material Stock Estimation

Statistics of Building Construction 1994-2004 (Source: Singapore BCA)

Macro analysis –

- form. geometry. topography

- perception. sensuous quality

- surface. materiality. land mosaics

4.- scale. system. complexity

how do we articulate multiple patterns across different spatial scales that can be observed in physical environment? What are their cross-scale relationships?

- process. temporal dimension

Carl Steinitz, 2008

Carl Steinitz, 2008

offensive versus defensive

Satellite image of multinodal heat island in Atlanta, GA. Darker tones denote highertemperature (Source: American Forests, 1996)

• SVF mean =.896 • SVF mean =.844

Energy flowSurface temperature prediction of Georgia Tech campus (P Yang , Y Lu, W Li 2009, working paper)

An illustration of Solar Availability analysis,From Atlanta Region to Downtown

Solar Assessment

Regional-scale

Urban-scale

Solar Assessment –block-scale

Urban, suburban and rural neighborhood typologies selected from Atlanta region and illustrations of their planning parameters

Urban Suburban RuralIncoming mean solar radiation 1,300 1,450 1,500

-form. geometry. Topography

- perception. sensuous quality

- surface. materiality. land mosaics

-- scale. system. complexity

5.- process. temporal dimension

Stochastic process in time: how do we move urban change toward sustainability?

1982, K=0.023 1988, K=0.022 1994, K=0.016

ecological processes, spatial and temporal scales (ecological process in different patch size)

Large patch benefit: higher diversity and “Sponge” effect for hydrology

0-100m2 tree replacement

plant competition

<1ha small mammal life cycle

<100ha succession

<100km2 large species movement

Space and Time scales relationship (Forman, 1995)

Hydrological effects of urban sprawl

TaipeiTaipei Basin

Shangshen Typhoon, 2000 ,11

Form of City becoming less compact in the process ofurbanization

1982, K=0.023 1988, K=0.022 1994, K=0.016

K = 2√(πA)/ p :

Compactness index

Shape of vegetation-patches becoming more

fragmented in the process of urbanization

1982, D= 1.2228 1988, D= 1.2234 1994, D= 1.2698

D = 2 s = 2 * (log p/ log A) :

Fractal dimension

Landscape heterogeneity becoming higher

1982, H’=0.7751 1988, H’=0.9603 1994, H’=1.0326

H' = -∑Pi lnPi :

Shannon diversity index

Changing hydrological regime from 1980s to 1990s

1980 1990

1. Assessing ecological effects of large-scale urbanization

Land Development

Runoff Ratio

S=1.23

average runoff ratio in 1980s

average runoff ratio in 1990s

S=1.91

Does it Imply a threshold point in 1990?

Taipei Eco-City Master Plan1st Place in Planning Competition, Taipei Municipal Government, 1998

2025

1998

1978

• Three-tier planning system:1. Eco city policy2. Land use evaluation and the mechanism of

land management3. Planning & design guidelines

scenario planning of Taipei’s ecologica corridors

The Future of the City 2108 Atlanta

Can we reverse sprawl?. eco-infrastructure. mobility infrastructure. eco-Acre Transfers

Georgia Tech Team: Richard Dagenhart, Ellen Dunham-Jones, et al.