Great ci­ties must pro­tect their wa­ter­sheds

The Myanmar Times - - Views - MARK BUCHANAN news­room@mm­times.com

THE world’s great ci­ties could hold the key to the pros­per­ity of the hu­man race. Yet a com­pre­hen­sive new study points to a wor­ry­ing trend: The wa­ter they need to grow is get­ting more ex­pen­sive be­cause they’re fail­ing to pro­tect the na­ture that pu­ri­fies it.

Ci­ties are amaz­ing en­gines of pro­duc­tiv­ity. As the hubs of our mod­ern so­ci­eties, they mix to­gether peo­ple with a di­ver­sity of skills and cre­ate fer­tile ground for learn­ing and in­ven­tion. In many re­spects, big­ger tends to be bet­ter. Larger ci­ties have more patents and in­ven­tions per per­son, and achieve bet­ter en­ergy and re­source ef­fi­ciency thanks to economies of scale. For ex­am­ple, they re­quire less con­duct­ing ca­ble per per­son to carry elec­tri­cal power where needed.

Con­cen­trat­ing peo­ple in ci­ties also leaves more space for na­ture. It’s one rea­son that Paul Romer, re­cently ap­pointed as chief econ­o­mist of the World Bank, has been cham­pi­oning the idea of char­ter ci­ties – brand-new ci­ties that we could build and use to ex­per­i­ment with large-scale in­no­va­tions in tech­nol­ogy or gov­ern­ment. Dozens of such ci­ties could help us ex­plore more sus­tain­able ways of liv­ing, and also help meet the need to house many of the ad­di­tional 3.4 bil­lion peo­ple ex­pected to be liv­ing by 2050.

It turns out, though, that pro­tect­ing the sur­round­ing na­ture is also cru­cial for ci­ties to work. Any city draws its clean wa­ter from a nat­u­ral water­shed area – some close by, oth­ers far­ther away. The rain­fall that drains into the area is fil­tered and pu­ri­fied by nat­u­ral land cover – forests, marshes and grass­lands – be­fore en­ter­ing as the “raw wa­ter” of treat­ment fa­cil­i­ties. The wa­ter for New York City, for ex­am­ple, comes from large reser­voirs lo­cated an av­er­age of 100 miles (160 kilo­me­tres) away in up­state New York.

As ci­ties have grown, the land in their wa­ter­sheds has been cleared to make way for hous­ing, fac­to­ries and agri­cul­ture. As a re­sult, wa­ter qual­ity has de­clined. Agri­cul­tural run-off, for ex­am­ple, boosts con­cen­tra­tions of ni­tro­gen, phos­pho­rous and sed­i­ment. Treat­ment cen­tres must then re­move these im­pu­ri­ties, re­quir­ing the use of in­creas­ingly com­plex and costly tech­nolo­gies.

A new study, led by ecol­o­gist Robert McDon­ald of the Wash­ing­ton­based Na­ture Con­ser­vancy, sug­gests that the cost of wa­ter treat­ment is be­com­ing a very large bur­den on a global scale. Look­ing at changes from 1900 to 2005 in the wa­ter­sheds of 309 large ci­ties, all with pop­u­la­tions larger than 750,000, it finds that more than 90 per­cent have suf­fered degra­da­tion, and that nearly one-third ex­pe­ri­enced a sig­nif­i­cant rise in treat­ment costs – many by more than 50pc.

The study con­firms what en­vi­ron­men­tal economists pre­vi­ously only sus­pected: The loss of nat­u­ral wa­ter pu­rifi­ca­tion ca­pac­ity is sys­tem­at­i­cally in­creas­ing the cost of treat­ment around the globe. The best es­ti­mate puts the added ex­pense at more than US$5 bil­lion per year. And it’s set to get worse: Water­shed degra­da­tion is ex­pected to be­come more se­vere in the next decade or so, as crop­land con­tin­ues to ex­pand. By 2030, global fer­tiliser use is pro­jected to rise by nearly 60pc.

The les­son is that our ci­ties will re­quire con­certed in­vest­ment in water­shed preser­va­tion. The good news is that it need not be ter­ri­bly ex­pen­sive: Tar­geted projects can make a big dif­fer­ence. Since 1997, for ex­am­ple, the New York City De­part­ment of En­vi­ron­men­tal Pro­tec­tion has moved to pro­tect more than 130,000 acres of valu­able water­shed, and the city now has very low wa­ter treat­ment costs rel­a­tive to other US ci­ties.

New York’s for­ward think­ing can and should be repli­cated glob­ally. McDon­ald and oth­ers es­ti­mate that roughly one in four ci­ties – home to about 800 mil­lion peo­ple – could reap a pos­i­tive re­turn on in­vest­ment aimed at con­serv­ing wa­ter­sheds. In other words, it’s worth do­ing, and it would be an im­por­tant step to­ward se­cur­ing the kind of en­vi­ron­ment we need to sur­vive. – Bloomberg

Mark Buchanan, a physicist and sci­ence writer, is the au­thor of the book What Physics, Me­te­o­rol­ogy and the Nat­u­ral Sciences Can Teach Us About Eco­nom­ics.

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