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BBC NEWS | Science/Nature | Finding green in the concrete jungle
<http://news.bbc.co.uk/1/hi/sci/tech/5072642.stm>

In Depth: URBAN PLANET
http://news.bbc.co.uk/1/hi/in_depth/world/2006/urbanisation/default.stm
        
Last Updated: Monday, 19 June 2006, 12:12 GMT 13:12 UK
Finding green in the concrete jungle
By Richard Black
Environment correspondent, BBC News website
Apart from a few lower members of the animal kingdom, no-one other than human 
beings build cities.
The polluted Nanhu Lake in China's Chongqing
Chongqing in China is growing fast - so is the pollution

They are totally artificial constructs and in them we live artificial lives. 
We travel differently, eat different food,
receive water and energy through pipes and wires, live in different kinds of 
buildings, do different jobs.

All of these things come with an environmental price-tag. Given that the 
world's urban population is expanding at such a
rate, it is worth asking what are the numbers on that price-tag, and whether 
they are higher or lower than the
environmental cost of living a rural life.

Does a person produce more or less carbon dioxide on moving from the countryside to the 
city? If the answer is "less",
how should that be offset against a bigger contribution to urban smog? Is 
trash piling up on a street corner better or
worse than excess fertiliser running from farmland into the water supply?

See the world's most polluted cities

How far does a city's environmental footprint extend beyond its boundaries - 
to the natural resources which feed it with
water and food, or to the other side of the planet which feels its greenhouse 
gas emissions?

There is no simple answer.

Rush from rural

"What is needed is research that focuses on the large-scale, long-term 
environmental changes, not just on the immediate
impact of cities," concludes the International Human Dimensions Programme on 
Global Environmental Change (IHDP), a
global research alliance.

A farmer from the Dabieshan Mountain area in central China
China has seen massive migration from areas of low agricultural productivity 
to coastal cities

"Until recently, this has been quite unexplored territory," it says. It is 
territory which badly needs exploration if
the full impacts of 21st Century urbanisation are to be fully understood.

"In China, 125 million people have moved from areas of low agricultural 
productivity to coastal cities - that's 25% of
the workforce, and you've got another 25% waiting to move," says John 
Harrington from London's Overseas Development
Institute (ODI).

"The rise in fossil fuel consumption in Chinese cities is now costing between 
three and six million life-years per year.
Asia is going to see a ten-fold increase in the solid waste management burden by 
2025."

Fuel use

Fuel use, intimately connected to urban pollution and greenhouse gas 
emissions, demonstrates exquisitely the problems in
trying to compare the ecological footprint of the rural and urban dweller.

In 2002, the United Nations Development Programme (UNDP) focused much of its 
Human Development Report on China.

"Rural residents consume less than 40% of the commercial energy used by their 
urban counterparts," it concluded.

Tokyo skyline
In Tokyo, air quality has improved over the past 50 years

"However, if biomass [principally wood-burning] is included, the average 
person in the countryside uses nearly one-third
more energy than a city dweller."

So the rural resident apparently contributes more to global climate change 
than the urban citizen - but the equation
hinges on how the energy is produced.

If "commercial energy" used in cities - principally electricity - is derived 
from renewable sources or nuclear stations,
the urban dweller wins the eco-prize hands down. But if the rural citizen 
burns nothing but trees and always replaces
them, he or she becomes "carbon neutral" and scoops the award.

"Urbanisation is a complex issue," observes Bert Metz of the Netherlands 
Environmental Assessment Agency (MNP), co-chair
of the Intergovernmental Panel on Climate Change (IPCC) working group which 
looks at economic and social projections.

"Generally speaking, people in cities use more transportation and energy 
services than in the rural areas and rely less
on biomass. Certainly that is a factor driving up greenhouse gas emissions, but 
there are many other drivers too."

Those other drivers include two further trends of our time, rising population 
and economic growth, whose imprint is
difficult to distinguish from that of urbanisation.

Rules for the rich

In any case, talk of a "city environment" brings a basic question - which 
city?

In London and Tokyo, air quality has improved over the last 50 years. In 
Shanghai and Kuala Lumpur, it has gone down,
though there are signs of improvement elsewhere in the developing world.

"It has happened in Delhi, for example, where there has been a huge 
improvement in air quality by substituting liquefied
petroleum gas [LPG] for diesel in vehicles," observes John Harrington.

"Partly it is just that as cities become richer they can clean their act up, 
but it's also how vocal the middle classes
become, which in India counts in a way it doesn't yet in China.

"But there's a paradigm question here - whether cities are being urged to 
move away from the traditional 'grow first and
clean up later paradigm' to a 'sustainable growth paradigm'."

The "sustainable city" is a concept which has received a lot of academic 
attention in recent times.

An Australian group, the Halifax EcoCity Project, has developed what it calls an 
"ecological measuring stick".

Essential elements of sustainable urban development include, it says:

    * extensive use of vegetation to filter pollution, prevent the "heat 
island" effect and capture carbon dioxide
    * purification and recycling of all water and waste
    * 100% supply of renewable energy
    * a sustainable food supply which does not deplete nearby lands and grow 
as much as possible with city limits

The EcoCity concept, says Bert Metz, would have a major impact on greenhouse 
gas emissions.

"How cities are planned definitely has an impact. Are there many trees 
planted, which reduces the need for cooling? How
are houses built - that has a huge effect on greenhouse gas emissions."

But by the Halifax yardstick, virtually every city in the developed as well 
as the developing world would fail the
sustainability test.

Slices of life

Planning cities to allow for green spaces, wildlife, trees and watercourses 
can have a huge benefit on people as well as
on the natural environment, says David Goode, a visiting professor at 
University College London and former director of
the London Ecology Centre.

        
There's a lot of evidence that both physical and mental wellbeing increases 
with access to nature and green spaces
David Goode, University College London

"When you've got more than half the world's population living in urban areas, 
it's crucial they have access to some kind
of ecological area within a stone's throw of where they live," he argues.

"There's a lot of evidence that both physical and mental wellbeing increases with 
access to nature and green spaces."

Since the big clean-up began half a century ago, many British cities have 
become home to the fox, while birds such as
the black redstart have become "urban specialists".

But is it real nature, or just a designed and planned imitation?

"It is different," says Dr Goode, "but you can encapsulate a lot of the 
features of natural habitat within a city
environment."

In any case, much of the world's countryside is far from "natural", shaped as 
it has been by centuries of human
agriculture, in some cases producing vast prairies of monoculture monotony 
where hardly a bird is heard.

But fundamentally people are not flocking to the vast cities of Asia and 
South America with nature and green spaces in mind.

They are coming for jobs, to improve their economic and social prospects.

It may be sobering then to consider the UNDP's judgement on China's 
urbanisation and its concomitant rising toll of
pollution and waste: "Environmental factors are likely to constrain, or even 
reverse, social and economic progress."

It is the same old message: societies neglect environmental progress at their 
economic peril.

Richard.Black-INTERNET@bbc.co.uk