Megac­i­ties face a grow­ing risk from the planet


ON MON­DAY, the world’s pop­u­la­tion will of­fi­cially reach 7-bil­lion ac­cord­ing to the United Na­tions. Reach­ing that his­toric land­mark re­minds us of the chal­lenges, in­clud­ing here in Africa, cre­ated by an ever-in­creas­ing num­ber of hu­mans on the planet.

Grow­ing pop­u­la­tions are also driv­ing an­other trend — ur­ban­i­sa­tion through mi­gra­tion. In 1800, less than 3% of the world’s pop­u­la­tion lived in cities, yet by the end of 2008, this had risen to more than 50%, and there were 26 megac­i­ties (cities of 10-mil­lion or more in­hab­i­tants), in­clud­ing Lagos, Cairo and Is­tan­bul.

De­spite the eco­nomic suc­cess of megac­i­ties, gov­ern­ments are pre­par­ing for the grow­ing risks these ur­ban cen­tres pose. For in­stance, will it be pos­si­ble to con­tin­u­ally meet the ev­ery­day de­mands for food, water and health­care, and also deal with the vul­ner­a­bil­ity of megac­i­ties to en­vi­ron­men­tal stresses, made worse by the ef­fects of cli­mate change?

There is al­ready cause for some alarm. The tsunami in Ja­pan this year forced Tokyo to re­con­sider its ap­proach to nu­clear power and to pro­tect­ing its cities. The 2003 heat wave in Paris was so dev­as­tat­ing be­cause the pub­lic and au­thor­i­ties were un­pre­pared for deal­ing with such ex­treme weather con­di­tions, which were made worse by build­ing prac­tices, es­pe­cially the lack of air-con­di­tion­ing.

Megac­i­ties across the world will con­tinue to grow, as will other large ur­ban con­glom­er­a­tions. En­ergy de­mands will in­crease. The as­so­ci­ated in­creased car­bon emis­sions are con­tribut­ing to global warm­ing and pose their own cli­mate risks. In China, where peo­ple are sub­sidised to move from the coun­try­side, cities have grown by a fac­tor of two in only five years. The lo­cal ur­ban “heat is­land” ef­fect means tem­per­a­tures are in­creas­ing about three times faster than the rate of tem­per­a­ture rise over global and national land ar­eas.

The main risk for river­ine megac­i­ties on coastal plains is their in­creas­ing vul­ner­a­bil­ity to ris­ing sea lev­els and river flood­ing, such as those dev­as­tat­ing Bangkok right now. There will be fur­ther episodes such as the one in New Or­leans six years ago, when it was hit by Hur­ri­cane Ka­t­rina, with­out ad­e­quate pro­tec­tion and flood­warn­ing sys­tems.

The larger the ur­ban area, the greater the dam­age nat­u­ral haz­ards can in­flict; and in­creas­ingly it may be im­pos­si­ble to pro­tect life and prop­erty even if there is a per­fect warn­ing sys­tem. As a re­cent hur­ri­cane in Hous­ton showed, there is now in­suf­fi­cient time to evac­u­ate some cities safely, even highly de­vel­oped ones.

So there is a press­ing need for cities to de­velop emer­gency refuge ar­eas. In some cases these may al­ready ex­ist. In most cases, how­ever, refuges will need to be built from scratch. Thus, en­gi­neers and plan­ners are con­sid­er­ing how to iden­tify and de­sign such emer­gency cen­tres, and how these should be con­nected to the wider ur­ban sys­tem.

Be­cause of the fail­ures to deal with some of the re­cent haz­ards af­fect­ing megac­i­ties, gov­ern­ments are plan­ning for mul­ti­ple haz­ards and are de­vel­op­ing strate­gies for man­ag­ing the range of en­vi­ron­men­tal fac­tors that could emerge. Other re­search teams are col­lab­o­rat­ing in con­struc­tion of “sys­tem dy­nam­ics” mod­els for the op­er­a­tion of in­fra­struc­ture, environment and the so­cioe­co­nomic aspects of megac­i­ties.

These mod­els re­sem­ble well-known com­puter pro­grammes for global cli­mate change and its in­ter­con­nec­tions to eco­nomic de­vel­op­ments. These will help cities to pre­dict which haz­ards they face and help them de­cide how to pre­pare.

What these mod­els need is im­proved avail­abil­ity of rel­e­vant en­vi­ron­men­tal and so­cioe­co­nomic data. Here, in­ter­na­tional agen­cies such as the World Health Or­gan­i­sa­tion and the World Me­te­o­ro­log­i­cal Or­gan­i­sa­tion, as well as gov­ern­ments, need to col­lab­o­rate with a wider range of or­gan­i­sa­tions and make max­i­mum use of new me­dia. This will bet­ter en­able data show­ing how peo­ple ex­pe­ri­ence rapidly oc­cur­ring haz­ards such as tor­na­does and phe­nom­ena such as loss of crops from ris­ing sea lev­els and salt pen­e­tra­tion.

For­tu­nately, megac­i­ties have a global or­gan­i­sa­tion for in­for­ma­tion ex­change and col­lab­o­ra­tion called C40 Cities.

The agenda in­cludes en­hanced in­ter­city co-op­er­a­tion on poli­cies for deal­ing with haz­ards and putting more pres­sure on gov­ern­ments to as­sist, es­pe­cially with fi­nance, data and strate­gic pri­or­i­ties.

Hunt is Vice-chair­man of Global Leg­is­la­tors Or­gan­i­sa­tion for a Bal­anced Environment. Li is Pro­fes­sor of Me­chan­i­cal En­gi­neer­ing at the Univer­sity of Hong Kong.

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