Defining “Sustainability”

Danny Harvey

Department of Geography

University of Toronto

Four Principles of Sustainability (HOK Guidebook to Sustainable Design)

• Substances from the Earth’s crust must not systematically increase in the ecosphere

• Substances produced by society (man-made materials) must not systematically increase in the ecosphere

• The productivity and diversity of nature must not be systematically diminished

• There must be fair and efficient use of resources to meet human needs (basic needs for all take precedence over providing luxuries for the few)

I would add a 5th and 6th principle of sustainability:

• Human energy needs must be met entirely from renewable energy sources, without degrading the longterm capacity of nature to supply energy renewably

• The local rate of consumption of freshwater must not exceed the rate at which freshwater is supplied through the hydrological cycle in excess of ecological needs

There are both resource and environmental constraints on

sustainability

• Resource constraints – resources eventually become prohibitively expensive

• Environmental constraints – environmental consequences undermine basic life-support systems or create societal instabilities

Yearly Global Mean Temperature Changes, 1856-2004, and 5-year running mean

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

1855 1880 1905 1930 1955 1980 2005Year

Tem

pera

ture

Cha

nge (

oC)

-0.5

0.0

0.5

1.0

1000 1200 1400 1600 1800 2000

Year

Dev

iatio

n (

oC

)Directly Observed

Proxy Indicators, 20-year movingaverage

Global or NH Temperature Variation, 1000-2100

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

1000 1200 1400 1600 1800 2000 2200

Year

Dev

iatio

n (

oC

)

Observed

High Model Projection

Low Model Projection

Mann et al (1999) NH Proxy, 20-year moving average

Stabilization of Climate at (hopefully) non-catastrophic levels (CO2 peaking at 450 ppmv), andSustainable Development (requiring, among other things, a Sustainable Energy System (one based on

Renewable energy)) are Flip Sides of the Same Coin (there is no conflict between the too):

Both require completely phasing out the use of fossil fuels (the former before 2100 AD).

The longterm per capita energy use consistent with sustainability depends on the human population. For populations peaking at 8-9 billion, per capita energy

use in OECD countries needs to fall by at least a factor of 4 (and renewable sources

of energy rapidly ramped up)

0

4

8

12

16

20

2000 2020 2040 2060 2080 2100

Carbo

n Emi

ssion

(Gt C

yr-1

) Coal

Oil

Natural Gas

350450

550

650

750

Trade-off between amounts of carbon-free power required at various times in the future and the rate of reduction in energy intensity required for stabilization at 450 ppmv CO2

0

5

10

15

20

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

Rate of Energy Intensity Decline (%/yr)

Requ

ired C

arbon

-Free

Powe

r (TW)

2050

2025

Global Primary PowerSupply in 2000 (13.3 TW)

Energy and the New Reality: 

Facing up to Climatic Change 

Island Press, Washington 

Late 2008 Publication

A Sourcebook on Low-Energy Buildings and District Energy

Systems: Fundamentals, Techniques, and Examples

  James & James / Earthscan (London)

 Published July 2006