China’s response to the encroachment¹ of its northern deserts on cities such as Beijing is a tree-planting exercise, the Three-North Shelterbelt.

面对中国北方沙漠对北京等城市的侵蚀，中国政府的对策是植树造林：建造三北防护林。

But while the so-called Green Great Wall is one of the world’s most ambitious environmental projects, it is just one of many attempts to protect cities against pollution, storms and temperature rises by tapping into a valuable resource: nature.

不过，虽说这个所谓的绿色长城是世界上最雄心勃勃的环境工程之一，但它只是人类利用一项宝贵的资源——大自然——保护城市免受污染、风暴和气温升高侵扰的诸多尝试中的一个。

It has long been known greenery improves air quality, which is why large urban parks, such as the Maidan in Kolkata, India, or New York’s Central Park, are often referred to as the lungs of the city.

人类很早就知道绿色植物可以改善空气质量，这就是为什么大型城市公园——如印度加尔各答马坦公园(Maidan)或纽约中央公园(Central Park)——常被称为城市之肺。

But as pollution and increasingly intense storms threaten urban areas, planners are starting to recognise that nature has more than one purpose.

但随着污染和日益强烈的风暴危及城市地区，规划者们开始认识到，大自然还另有用途。

So-called green infrastructure² can be used to soak up water that can otherwise inundate³ municipal areas.

所谓的绿色基础设施可用来吸收能够淹没城市地区的洪水。

When superstorm Sandy hit New York and New Jersey⁴ late in 2012, for example, storm water flowed through subway tunnels and shut down ground-level power and communications networks.

例如，2012年晚些时候超级飓风桑迪(Sandy)袭击纽约州和新泽西州时，暴雨带来的降水灌进了地铁隧道，并导致地面电力和通讯网络中断。

The frequency, unpredictability and intensity⁵ of storms is overwhelming a lot of conventional systems, says Jason Scott, co-managing partner at Encourage Capital, an asset management firm specialising in investments that can help to resolve social and environmental problems.

Encourage Capital联席管理合伙人杰森•斯科特(Jason Scott)表示：风暴的次数之多、预测之难和强度之大，令很多传统的系统难以应付。Encourage Capital是一家资产管理公司，聚焦于能帮助解决社会和环境问题的投资。

Severe rainstorms are responsible for sending large amounts of untreated water — containing everything from motor oil and lawn fertiliser to raw sewage — into drinking water systems and open waterways.

大暴雨会使大量未经处理的水——含有从机油、草坪肥料到污水等各种污染物——涌入饮用水系统和开放水道。

In places like Milwaukee and Chicago, storm water is combining with sewer⁶ overflow⁷ and going in people’s homes, so it’s not a theoretical problem — it’s very real, says Mr Scott.

在密尔沃基、芝加哥等地，暴雨降水与下水道溢出的污水一道涌入民宅，所以这不是一个理论问题，而是一个非常实际的问题，斯科特说。

Green infrastructure — such as grass roofs, planters and permeable pavements that allow water to filter the soil below them and soak up storm water — can help prevent this.

绿色基础设施——例如草坪屋顶、绿植以及可让雨水渗入下面土壤并吸收暴雨降水的透水路面——可以帮助防止这种情况发生。

The idea behind the green infrastructure approach is to mimic⁸ the way nature handles water, says Larry Levine, senior attorney in the water programme at the Natural Resources Defence Council, a US environmental group.

绿色基础设施模式背后的理念是要模拟大自然处理水的方式，美国环保组织自然资源保护委员会(Natural Resources Defence Council)水资源项目资深律师拉里•莱文(Larry Levine)说。

Nature can improve cities’ air quality.

自然可以改善城市空气质量。

In Ahmedabad, the Indian state of Gujarat’s largest city, where summer temperatures can be above 40C, a development plan includes linking the city’s Sabarmati River with lakes, building a series of parks and planting trees.

在夏季气温可超过40摄氏度的印度古吉拉特邦最大城市艾哈迈达巴德(Ahmedabad)，一项开发计划就包括将流经该市的萨巴尔马蒂河(Sabarmati River)与湖泊相连接，建造一系列公园，种植树木。

Such schemes can help to control summer temperatures, says Ian Mell, lecturer in planning and civic⁹ design at Liverpool university.

利物浦大学(Liverpool University)规划与城市设计专业讲师伊恩•梅尔(Ian Mell)表示，此类项目能够帮助控制夏季的气温。

They’re using trees and better management of the lakes and river to moderate the extremities¹⁰ of the climate, he says.

他说：他们正在利用森林以及对湖泊、河流更好的管理来缓和极端气候。

Other natural assets can be tapped, too.

其他自然资源也可以被利用。

In some parts of the world, mangroves are tremendous at flood protection and preventing soil erosion, says Mr Levine. Green infrastructure of that sort is very much part of the toolkit for climate change adaptation.

在世界的一些地方，红树林在防洪和防止水土流失方面作用巨大，莱文说，此类绿色基础设施恰恰是那种适应气候变化的手段。

But while green infrastructure does much to tackle flooding, air pollution and inhospitable city temperatures, it can be hard to persuade developers and investors¹¹ it is worth the extra money.

虽然绿色基础设施在很大程度上可以应对洪水、空气污染以及极端的城市气温，但很难说服开发商和投资者相信值得为此投入更多资金。

It’s about learning how to understand the upfront costs and how they translate to benefits over time, says Eric Mackres, building efficiency manager at the World Resources Institute’s Ross Center for Sustainable Cities.

世界资源研究所(World Resources Institute)罗斯可持续城市中心(Ross Center for Sustainable Cities)的建筑节能管理人埃里克•麦克雷斯(Eric Mackres)说：这事关学会如何理解前期成本以及它们日后如何转化为收益。

This is a particular difficulty in growing economies, where the race to develop means that urban centres are being built at terrific speed, often without sufficient planning.

在成长型经济体推广尤为困难，因为这些经济体的发展竞赛意味着，城市中心正以惊人的速度建设，但通常没有进行充分规划。

The scale of development means climate change gets addressed later, says Mr Mell.

发展的规模意味着，气候变化问题被放到后面解决，梅尔说。

Some older cities are creating financial incentives¹² for developers to go green.

一些历史悠久的城市正在提供经济方面的奖励，激励开发商开发更多绿色基础设施。

In Washington DC, for example, regulations have been introduced that make it mandatory¹³ for buildings in certain areas to include green infrastructure.

例如，华盛顿(Washington DC)已出台相关法规，强制要求某些区域的建筑必须包括绿色基础设施。

The city has introduced a stormwater retention¹⁴ credits trading scheme for developments where this is not technically¹⁵ feasible.

华盛顿还出台了一个雨水储存积分交易机制，面向那些不具备建设绿色基础设施技术条件的开发项目。

Credits, which are traded in an open market, can be bought from developers operating in parts of the city not covered by the regulations but who have nonetheless invested in sustainable projects.

可在公开市场交易的积分，可以从在不受该规定管辖的城市区域运营、但还是投资了可持续发展项目的开发商那里购买。

Mr Scott believes that more of these kinds of innovative¹⁶ financial arrangements will be needed to increase the adoption¹⁷ of urban green infrastructure.

斯科特认为，未来需要更多此类创新金融安排，以增加城市绿色基础设施的应用。

A lot of the solutions are financing solutions because the capital markets don’t know how to value these projects, he says.

他说：很多解决方案都是融资方案，因为资本市场不知道如何估值这些项目。