Smog crisis, Harbin, China, Oct. 21, 2013. Cheng Qiang/ Imaginechina/Corbis
November 24, 2013
Cities
are the places where people have most modified nature. Buildings protect people
from extremes of heat and cold by air conditioning. Vegetation is managed by
elaborate planting, watering and fertilization systems. Introduced and invasive
species often dominate, if not overwhelm, native ones. Rivers are channelized,
embanked and diverted. Water supplies are pumped from deep aquifers and piped
from distant reservoirs, often hundreds of kilometers away. Health care
systems, albeit variable in effectiveness and accessibility, protect much of
the world’s urban population from the worst communicable diseases.
Urban
areas are often comfortable, congenial and civilized places in which to live,
yet urban dwellers ignore nature at their peril. History shows that large
modern cities are vulnerable to extreme events. To recall a few recent
examples: Hurricane Sandy on the east coast of the United States in 2012; the
2011 Tohoku earthquake and tsunami in Japan; the fires in Dhaka in 2010 and in
Manila in 2011; the Eyjafjallajökull eruption in 2010 that left an ash cloud
over Europe; the list could go on and on. Meanwhile, every day nature affects
our urban lives through disease vectors; rain, sleet and snow; floods and
droughts; heat waves and cold snaps; landslides and subsidence; tree falls,
weed and mold infestations and insect pests.
To cope
with all these natural events, cities have to be well managed and well
governed. The degree to which individual cities can provide security and
protection for their inhabitants is in part related to the severity, magnitude
and frequency of natural events; in part influenced by the extent to which
buildings and infrastructure are able to withstand those events; and in part
dependent upon the resilience of urban society. The latter comprises its
ability to adapt to both abrupt major events and to the slower more gradual
changes, such as the consequences of local urban growth and land-use change and
of global economic, technological and environmental change, especially climate
change. Improving urban conditions requires taking a holistic view, seeing the
problems at a range of scales from the individual household to the whole
metropolitan region, appreciating the relationship between an individual’s
daily activities and the changing character of the city, and realizing how
altering one component of the urban environment affects a whole series of other
aspects of the built-up area.
The Wu Xing
In modern
municipal administrations, responsibilities are usually divided into strict
professional departments, with planning and environment frequently separated
from public health, education, finance and engineering. Addressing
environmental issues usually requires cutting across these departmental
divides. Today many urban managers, designers, planners and scientists are
looking at cities as complex social-economic-natural ecosystems in which political,
social, cultural and economic phenomena interact with the components of the
natural environment.
Societies
have long recognized the importance of such interactions for human health. In
the eleventh century, the Persian scholar Avicenna (Abu Ali Al-Husayn ibn
Abdallah ibn Sina) wrote in his Canon of Medicine of the four humors: hot,
cold, moist and dry, which were related to the weather. Medieval Europeans
described the four humors as blood, phlegm, yellow bile and black bile, again
relating them to the seasons, but also to elements of nature.
This
four-fold division may be compared to the five traditional elements of the
Chinese Wu Xing: water, metal, earth, fire and wood, which are used as the
natural subsystem framework for analysis of complex urban systems in China. In
the United States, much recent research has explored the nature of coupled
human-natural systems or urban socio-eco-biophysical systems, because the
understanding of urban life gained from the social, behavioral and economic
sciences has to be linked to ecological and earth surface processes; the latter
to explain how nature works in cities under complex human influences. This
approach helps to develop workable reactions to nature’s responses to
urbanization and the effects of environmental change on urban inhabitants.
In the
current Chinese social-economic-natural complex ecosystem approach, which uses
the Wu Xing in a modern context, the five natural elements form a physical
subsystem, with economic, social and scientific subsystems as well. The core
subsystem features three elements with which to deal with the Wu Xing:
knowledge, culture and institutions. These three elements may be considered to
represent the key human drivers of urban change and management. Knowledge
embraces science and technology together with traditional understanding and
community awareness. Institutions range from governments to corporations and
professional and influential civil society elites, and include urban management
systems and non-governmental conservation and environmental organizations.
Culture embraces lifestyles and family life (which dictates size and type of
dwellings), as well as the way residential preferences and attitudes to nature
affect the character of the built environment and the types and amount of urban
green space. Human use of natural areas within and around cities varies greatly
with social factors including age and ethnicity.
The
multiple environmental tests faced by modern cities need long-lasting
sustainable responses that often require thinking over much longer timespans
than those between democratic elections of mayors or municipal councilors. The
knowledge available to municipal institutions is abundant, but not always in a
form that busy people can rapidly assimilate.
The five
Wu Xing natural components can be taken to deal with five critical spheres of
urban and global change: the atmosphere (fire or energy), the biosphere (wood
or life), the hydrosphere (water), the pedosphere (earth or soil) and the
geosphere (metal or minerals). These spheres overlap; water, essential for all
life, is found in the atmosphere, the pedosphere and the rocks of the
geosphere. Nevertheless, they offer a workable framework within which to
organize discussions about urban environmental challenges.
Element
1: Water
An
essential factor in the location of urban areas is drinking water. Most ancient
settlements were located on rivers or by springs. Many inhabitants sunk wells
and found groundwater within a few meters of the surface,while the Romans constructed
great aqueducts to carry water to the majority of their cities. By the
twentieth century most large cities depended on remote sources, such as the
surface water Mono Lake supply to Los Angeles; the 2,820-kilometer Libyan
network of pipelines carrying fossil groundwater from beneath the Sahara to
coastal towns, cities and farms; and the approximately 900-kilometer Ras Azzour
to Riyadh pipeline, planned to convey one million cubic meters per day from the
world’s largest desalination plant, to be located on Saudi Arabia’s Arabian
Gulf coast. Even so, many cities have inadequate supplies, with piped water not
available twenty-four hours a day, and many dwellings having, at best, a
standpipe or well within a few minutes’ walk. The quest for safe, clean, reliable,
accessible, affordable water remains. Combinations of water sources, such as
surface water from rivers, groundwater, rainwater harvesting, desalination and
water reuse are being adopted in many Asian cities, both on a well-planned
municipal basis (as in Singapore) or by a combination of public supply, private
enterprise distribution, individual household and business rainwater
harvesting, and well sinking (as in New Delhi).
Even more
serious is the provision of safe sanitation. Over the period from 1990 to 2013,
globally 1.9 billion urban and rural people gained access to sanitation.
However, around 2.4 billion people will be using unimproved, inadequate
sanitation facilities in 2015: not much of an improvement over the 2.7 billion doing so in 1990. Although much of the improvement was in towns and cities, the
trick is to do more than keep pace with the growth of global urban population.
The other
side of the water challenge is to deal with water excess. As the world’s urban
population has become increasingly located in tropical regions―because the only areas in which they can find land to build homes are
in floodplains prone to heavy thunderstorms, cyclones and rapid storm-water
runoff, more and more people are becoming exposed to flood
risks. That the urban areas are paved or roofed only increases the risk of
local flooding within specific areas of the city. Such impacts are arising in
cities everywhere, but ways of reducing them exist, particularly in terms of
sustainable drainage systems, where the passage of water is slowed down and
infiltration is encouraged.
Element
2: Metal
The Wu
Xing element metal (or minerals) includes materials such as concrete, brick,
glass and steel used to build, furnish, decorate and ornament urban areas.
Concrete is particularly important as it is used for most of those paved
surfaces that accentuate flood risks, but is also part of flood control systems
in terms of urban drains and river flood walls. Abstraction of these minerals
means new uses have to be found for quarries or gravel pits. Significantly, the
topsoil from brick pits in China is put aside and later used to recreate
agricultural land at a lower level after the brick clay has been removed.
Success in reducing mineral raw materials use for urban institutions will
require applying the available knowledge of alternatives to concrete drains and
flood walls. This will involve particularly utilizing green infrastructure by
installing green roofs, grassed suburban waterways and more natural urban
rivers, including the converting of concrete channels or the reopening (or
daylighting) of small streams that were diverted into underground pipes when
the city first expanded.
Recycling
of construction and demolition waste is becoming widely adopted on a commercial
scale, particularly in large cities where transport costs are high. On another
scale, many poor rag-picking communities in South Asia are finding ways of
using other people’s waste materials to create building components, such as
walls made of glass bottles or flooring made of broken crockery. More advanced
materials reuse technologies including utilizing power station fly-ash for
brick substitutes and making plaster board alternatives out of pressed and
glued fragments of waste material. Although these forms of reuse are
commercially viable, cultural constraints sometimes prevent their adoption.
Several British supermarkets say they will not use recycled materials for fear
of contamination in their buildings.
Element
3: Earth
Earth
relates to soils and to the ground on which the city is built. Many cities
experience geomorphological problems such as landslides, subsidence and soil
erosion. Often these risks are not widely understood and purchasers of property
may not always know of their existence, particularly in cities where the events
happen infrequently, or generally only occur when the ground is disturbed and
local conditions are altered by construction activity. Cities with frequent
landslides, such as the Los Angeles and San Francisco areas, often have detailed
landslide hazard mapping. Hong Kong has developed a highly sophisticated
geotechnical control system to reduce landslide risk when building on steep
slopes. Helped by detailed computer mapping systems and databases, this
planning and building control system has reduced actual landslide damage
considerably. Other cities with similar geology and deeply weathered rocks have
begun to adopt some of the general principles, but elsewhere lack of information and building control
means that unwise excavations on landslide-prone terrain continue to put urban
lives at risk.
Subsidence
is a persistent problem that is often aggravated by urban development, mining
and groundwater extraction. Bangkok, Venice and Mexico City have frequently
suffered flooding as a result of irregular lowering of the ground surface
through groundwater removal. Restrictions on pumping and on unlicensed wells
can help to alleviate the situation. Mining for coal, salt and other minerals
also often leads to subsidence, long a problem in old coal mining areas in
Europe and North America. More difficult to cope with is the subsidence due to
subsurface cave collapse in soluble rocks such as the frequent sinkhole
formation events occurring in limestone in Florida. Again, careful geological
survey and building design can avoid the worst of these risks.
The major
volcano hazards threatening many cities are partly predictable by close seismic
monitoring of earth movements around the volcano. However, earthquake
prediction remains difficult, but effective earthquake emergency response
training and evacuation procedures can save lives. Good earthquake building
codes and building control measures can help to save even more lives. Tsunamis
caused by earthquakes are likely to become more threatening to coastal cities
as sea levels rise as a consequence of global warming, making existing sea
defenses less effective.
Element
4: Fire
Much of
the current global warming is related to fire, to energy consumption, particularly the use of fossil fuels in all types of machinery
including air conditioners and heating boilers—and the release of greenhouse
gases and heat into the atmosphere. The extra heat keeps large city centers
four or more degrees centigrade warmer than adjacent rural areas. However,
large parks, such as Hyde Park in London, reduce the heat island intensity
locally. This suggests that by careful planning of urban green spaces, heat
island temperatures can be lowered over larger areas. Many cities are
encouraging the creation of green roofs and establishing more parks and street
trees in an effort to reduce heat stress on hot days and to gain other health
benefits through exercise and recreation in the open air.
Urban
energy consumption has long had health consequences through air pollution. Much
of the smoke and sulphur dioxide from coal burning that affected Western cities
until the mid-twentieth century has gone, but has been replaced by new problems
due to oxides of nitrogen and photochemical smog associated with the widespread
use of oil and gas. Now extremely fine particles emitted from diesel engines
are seen as a major health issue. Rapid expansion of motor vehicle numbers and
traffic congestion has made such air pollution so severe in rapidly
industrializing cities of Asia and South America that measures to restrict car
use have been attempted. Urban traffic management remains a headache for most
cities despite massive investments in urban rapid transit systems and bus
services.
Congestion
and long queues of vehicles with their engines running are common problems in
Asia from Istanbul to Beijing and are growing in Africa from Cape Town to
Cairo. Road pricing and congestion charging are unpopular, although often
effective, because the private motor vehicle gives the driver the freedom to
travel, but that is also the freedom to pollute.
Urban air
pollution affects all living things within urban areas and far beyond, having
significant impact on agriculture as contaminated soils and plants will affect
food supplies. Further afield it has damaged forests, corroded iron work and
acidified lakes. In this way we can think of cities as having a pollution shed,
or contaminant fallout zone, extending well beyond the metropolitan boundary,
especially where carried away by the prevailing wind. The spread of acid rain
across northwestern Europe in the 1950s and 1960s showed how urban emissions
can become a transboundary problem, with the consequence of energy consumption
in one country being felt in another. International agreements can sometimes
cope with such issues, but the difficulties of getting a global agreement on
lowering greenhouse gas emission show just how hard this task can be,
regardless of how urgent the problem is. Some international coalitions of city
mayors already indicate a greater willingness of some municipal authorities to
collaborate than their national governments have done.
Such
external impacts of urban environmental problems now extend to the heart of the
Pacific Ocean, where a great gyre of finely comminuted plastic, dubbed the
Great Pacific Garbage Patch, threatens marine life. Some estimates say the
debris field is twice the size of the continental United States. Reducing these
far-reaching externalities is a collective urban problem that may be forgotten
among more immediate local issues, particularly as the voices of the small
Pacific Island states most seriously affected by damage to life in the oceans
and by rising sea levels are seldom listened to in international meetings.
Element
5: Wood
The Wu
Xing element wood implies the whole biosphere and all forms of life. The main
environmental concerns faced by city administrations often relate to human
well-being and social care, public health, to the avoidance of epidemics and
the impacts of disasters such as earthquakes. World Health Organization
environmental standards help urban managers to recognize when problems such as
air pollution are most severe, but sometimes economic and social considerations
make the adoption of the most effective alleviation and control measures
difficult. Measures such as mass immunization, avoiding contact with zoonoses
(infectious diseases, such as rabies, that are transmitted between species,
sometimes by a vector, from animals other than humans to humans) and preventing
the transmission of viral infections are not always effective in every major
city. The zoonosis West Nile virus appeared in the United States in 1999 in the
New York City area and spread rapidly across the country in 2002. Urban
practices and conditions such as the sale of live animals in many Asian markets
greatly affect the transmission of zoonoses. With malaria and dengue fever
remaining problems in many tropical areas, despite large international
campaigns, climate change may lead to such diseases moving poleward,
reappearing in cities from which they have long been eradicated. Urban
authorities and health institutions must be able to detect and control such
events rapidly.
Urban
environmental conditions and diseases also affect other urban animals and
plants. Bird and mammal survival in urban environments is affected by
collisions with manmade objects, food acquisition, predation and disease. Over
decades, many urban animals adjust to urban conditions, showing physical,
behavioral and genetic differences from their rural cousins. Small creatures
adapt and evolve more quickly than larger organisms. The way that dark peppered
moths (Biston betularia) survived in the soot of industrial cities demonstrates
how selection and evolution in cities can lead to distinct differences between
urban and rural animals. Changes can be difficult to spot; for example, white
blood cell (monocyte) counts are higher in house sparrows (Passer domesticus)
in urban areas than in rural areas, suggesting immune system adaptation to the
urban environment.
The food
urban people put out for birds and other animals helps to stabilize small bird
populations and to make predatory mammals more numerous. Nonetheless,
urbanization tends to reduce the numbers of large mammals, such as coyotes in
the United States. This allows meso-predators, such as domestic cats, more
opportunities to hunt, leading to the deaths of many of the most abundant urban
birds, with feral cats hunting more often than free-ranging domestic cats. At
the same time, there are concerns about the impact of agricultural chemicals in
the urban environment, with pesticides and herbicides influencing bird
populations, both directly and indirectly, by affecting birds’ growth,
development and survival. Some insecticides have had profound effects on
predatory bird populations, such as the sparrow hawk, but others have been used
for decades with no apparent impact on non-target organisms.
Complex
chemicals in the urban environment remain a major problem, with huge quantities
of pharmaceuticals being used every day. The world’s chemical and biomedical
companies are constantly searching for new products, materials and medicines.
The outcomes of their research and development help people everywhere to
improve their lives, avoid and recover from disease, grow higher-yielding crops
and manage plant and animal pests and diseases. Many characteristics of these
chemical compounds alter other chemical and biological processes and these
substances can enter food chains, particularly those of aquatic ecosystems,
into which they are carried by rainfall, sewer overflows, and releases from
unregulated manufacturing and farming activities. Not all pharmaceuticals are
removed in normal sewage treatment and their residues may be consumed by
microorganisms in river waters and thence by invertebrates that eventually are
eaten by fish, which may be caught for human consumption, or eaten by larger
fish that are harvested for human food. Evidence of serious problems for human
health from such contaminants is patchy, but their effects on fish are
well-documented.
Chemicals
are becoming a significant problem for water supplies and for the management of
fisheries in waters (lakes, ponds, reservoirs, canals or rivers) in and around
towns and cities, particularly those close to megacities, and large industrial
and transportation complexes. These chemical compounds are part of the urban
circulation of chemical elements, but many national or municipal environmental
monitoring agencies do not yet have either the means to test for them or
sufficient aquatic sites at which to monitor their concentrations. Many of
these compounds are known as persistent organic pollutants (POPs) and have been
found in high concentrations in fish off river mouths. They are also carried by
winds to agricultural areas so that the global extent of food transfers means
the POPs entering a food chain in one region may be carried to urban areas
remote from both their source and the locality where they first accumulated in
plants. Each individual city and each individual chemical user in that city, at
home or in industry, has a potential impact on the global movement of
potentially harmful chemical compounds.
The task
is to raise awareness of this invisible environmental problem and to take
measure to avoid accidental or unintended releases to air, water or soils. This
again is in part an issue of personal freedom to use pharmaceuticals, beauty
products and other toiletries against reducing the risk of contaminating the
environment and affecting food chains. Governments can only legislate to curb
the most severe risks, but other impacts, such as the careless disposal of
chemical compounds, have to be reduced through education that enhances
individual responsibility and awareness of potential side effects.
Another
important aspect of biota in the urban environment is the use of greenspace for
physical and mental health improvement. Contact with green space, even viewing
it from a hospital window, can improve mental health and feelings of well
being, while physical exercise in open space is sometimes prescribed by doctors
as an alternative to taking more pills. These health benefits are one reason
why local authorities in countries such as the United Kingdom have set open
space accessibility standards, suggesting criteria such as there should be a
green area within ten minutes’ walk or 600 meters of every home. Public housing
developments are often good at providing some open space, for example Singapore
features open-space facilities for children’s play within all its public
housing developments. Open-space requirements may be imposed on private
developers, but sometimes the space they provide is awkwardly situated, near
road intersections or relatively inaccessible, and not suitable for children’s
play or human relaxation.
Multiple
benefits are gained from well-located urban open spaces, particularly those
with trees and other vegetation. They improve health, reduce the urban heat
island effect, trap some pollutants, provide habitat for animals, support
biodiversity, can be parts of sustainable drainage systems and enhance the
visual attractiveness of towns and cities. Ideally such green spaces are parts
of green networks, or the green infrastructure of urban areas, helping to
provide a series of interconnected patches and corridors facilitating the
movement of both wildlife and pedestrians, be they walkers, cyclists or horse
riders. In many countries the principle of having such greenways or green
infrastructure plans is well developed, excellent examples being found in the
Netherlands and in Germany.
Our
Grandchildren’s Children
The
consideration of the five Wu Xing elements has led us to see that they are
indeed highly interconnected. Living in the city means that we are constantly
using the benefits, and sometimes the disservices, that they bring. We cannot
ignore the character of the air above us, the vegetation, animals and insects
around us and the ground beneath us any more than we can ignore the changes of the
traffic lights or the ringing of our cell phones.
What we
also have to be aware of is that ways of meeting these challenges do exist. In
rapidly developing urban areas, opportunities to forestall problems are found
both in the construction of new urban areas (as in the Tianjin Eco-city in
China that is being built in collaboration with Singapore) and in the way old
cities (like Freiburg, in Germany) have been converted into much more
sustainable places through a series of planning measures and retrofitting old
buildings.
The
brilliant 2008 Brunel Lecture by Peter Head demonstrated that existing
technologies could make existing urban areas more sustainable and cut greenhouse
emissions by 80 percent, by retrofitting buildings and changing transportation,
water, energy, and waste management systems. Cities would have comfortable zero
emissions mass transport; water collection, storage and recycling systems with
separate potable and grey water mains. Organic waste fed to biodigesters would
create both energy and compost for urban food growers. Buildings would be
heated and receive hot water through district combined heat and powers systems,
while much renewable energy would be generated by large scale desert solar,
tidal power and wind turbine installations. Distribution of goods and many
human needs would be greatly assisted by smart information systems. The ideas
and technologies exist, the willingness to change behavior, make appropriate
political decisions, and to act collectively for the benefit of future
generations is less evident.
The key
to the urban future is first of all to ensure that new developments are more
environmentally friendly than in the past and that the mistakes already made
are not repeated. Secondly, we have to retrofit both for sustainability, and to
mitigate and adapt to global climate change. The technologies are there, from
household solar panels to community-combined heat and power, from window boxes
to urban greenways. Integrated, holistic lateral thinking is required, along
with political emphasis on solving present problems through techniques that
will make urban living better for both present and future generations.
Sustainability is all about thinking of our grandchildren’s children.
Thinking
about and addressing urban environmental problems has to occur at all levels,
from the individual and the household to the local community, the individual
district or local authority, the metropolitan government and the whole urban
region including the surrounding countryside intimately linked to the major
city. Improvements are achieved through both small things and major schemes.
Changes
in habits—such as levels of home cooling or heating, reusing goods or recycling
of things no longer required, walking rather than driving—contribute to better
health, urban heat island effect reduction, slashing greenhouse gas emissions
and cutting back on use of raw materials. Achieving similar behavioral change
in the workplace adds to the benefits. Community schemes for recycling
furniture, composting garden waste, growing vegetables and even removing litter
from drains all assist in reducing some of the problems of materials use,
energy consumption and storm water flooding. This emphasizes that people can do
things for themselves and often can take a lead that prompts local government
into action.
Equally
important is the initiative taken by individual elected councilors to promote
environmental action through their local authorities. Mayors have been
particularly effective in some cities, exerting political leadership to reduce
the environmental impact of their municipality’s operations and encouraging
local businesses and the community to do the same. Some introduce fines to
discourage practices such as increasing paved areas around homes: Hamburg
charges for every square meter of extra impermeable paving put in place, in
order to reduce storm water flooding. Governments can show similar leadership.
Taxes can be used positively, for example the UK Landfill Tax has forced local
governments to greatly improve recycling rates. Charges for plastic bags in
supermarkets reduce plastic waste while deposits on bottles encourage reuse and
feed-in in tariffs for renewable energy encourage non-fossil fuel electricity
generation and prompt power companies to use biomass. Equally, the planning of
urban green space and green infrastructure can change the character of urban
areas and provide multiple benefits for local climate, water management and
biodiversity.
Such
measures can be found in many cities, sometimes as part of an integrated move
toward sustainability, but too often they are piecemeal responses to a series
of initiatives. Local biodiversity action plans are not necessarily linked to
climate change adaptation plans which in turn are not connected to transport
infrastructure policies and to public health strategies. Meanwhile, there are
many cities in which the imperatives of public order, water supply, health,
education and housing are so great, and the financial resources so small, that
little forward planning is possible. There are persistent differences between
successful growing cities with adequate investment and those with few financial
resources, whether in declining industrial areas or in regions where millions
of poor people are migrating from rural areas to cities in search of better
livelihoods.
Knowledge
is not simply that held by the technocrats and in libraries, it is also the
community understanding of local conditions and ways of coping with them.
Neither top-down nor bottom-up schemes alone will deal with all situations.
There has to be mutual respect, understanding, sharing and will to tackle the
challenges on all fronts.
Ian
Douglas is an emeritus professor in the School of Environment, Education and
Development at the University of Manchester. He is president of the
International Council on Ecopolis Development and author of Cities: An
Environmental History.