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before the second half of this century. Simultaneously, we face the chal-
lenge of renovating and altering our ex- isting building stock in order to reduce its ecological footprint. The majority of buildings in use by 2050 are already with us, so this often overlooked sector of the construction industry needs equal political and scientific effort, especially if we are to have any impact on climate change by reducing energy demand from the built environment. Particular care is required when considering how to improve energy efficiency in struc- tures worthy of conservation without damaging their integrity.
XX POSITIVE MOVES
There are, however, considerable grounds for opt imism; the impetus generated by the recognition of cli- mate change has galvanized society into action on many other environmen- tal issues. Of course, campaigners and academics have been aware of most of these problems for decades but a combination of legislation and building codes is at last driving new construc- tion toward sustainability in many parts of the world, while increased public un- derstanding of the issues is starting to generate consumer-led change in this and other areas of the economy such as food production, transport, packaging, consumer durables, and clothing. The introduction of sustainable for-
estry schemes is a step in the right direc- tion, although deforestation continues at an alarming rate. Strict enforcement will be required if timber for construction projects is only to be sourced from accredited sup- pliers. It is a matter of necessity to address the demand for unsustainably produced timber from countries that have not yet fully embraced this approach. Given how long this might take, in order to protect the remaining forests, it may be of even greater urgency to take direct action to stem the supply of this timber at the same time as growing alternative supplies and develop- ing replacement economic activities in the relevant areas. The environmental impact of secur-
ing heavy building materials is mini- mized where the most locally available
Local Action Moves the World •
www.icleiusa.org
Cities consume a vast number of resources.
materials are used. If the sub-soil is clay, it makes sense to build with bricks or even unfired clay. If sand and gravel or hard rock is plentiful, construction aggregates will be the obvious choice for the major structural elements. Local stone, if available, can be used
for facings and internal decoration. To this extent, surrounding geological con- ditions have always determined archi- tecture and it was only during the 20th century that the wholesale transporta- tion of building materials took place as a matter of course in wealthier nations, while architectural styles were perhaps foolishly exported to parts of the world where key raw materials were less plen- tiful. The poorest dwellings, such as mud huts and igloos, which use only the available materials, have something to teach the developed nations as interest is renewed in more sustainable building materials, particularly recycled or waste products such as straw and hemp, to name but two. In the language of global warming,
these could even be considered carbon- negative constructions, with the added bonus that straw and hemp are both ex- cellent insulants.
XX BEYOND PETROCHEMICALS
Building products derived from petro- chemicals will come under increasing pressure as global stocks of oil dwindle; it is thought that the peak of global oil production has already passed. In addi- tion, there are concerns about the envi-
ronmental impact of many plastics, par- ticularly the by-products of manufacture and disposal, together with the difficulty of recycling some substances. It is essen- tial to develop renewable alternatives to petrochemical products and great prog- ress has been made by innovative pro- ducers, even if the substitutions have yet to be widely available. Similarly, design- ers and specifiers will have to find alter- natives for materials derived from other minerals because rising international demand competes for limited resources, particularly given the pace of economic development in China and India. Increased pressure on water sup-
plies as a result of development is an age- old problem that has given rise to numer- ous conflicts. The profligate use of water in developed nations is being curbed by a combination of rising prices, public education, and improved manufacture of sanitary goods. Rainwater harvesting is becoming more common on new devel- opments in order to minimize the burden added to the existing infrastructure. In areas of the world where water is already a scarce commodity and consumption is much higher, further settlement will have to be very limited unless the science of groundwater can ensure that increased abstraction will be sustainable given the particular sub-surface conditions of each catchment area. Geological conditions also inform
the design of drainage systems. The new discipline of SUDS (Sustainable Urban Drainage Systems) recognizes that an in- tolerable burden has been placed upon
PLANET EARTH \\ CITY EXPANSION
SANWUISUSP
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