Green roofs
A
AAcross the world's cities it has become an ordinary sight: rooftops planted with turf, vegetable plots and dense greenery. Investment in these green roofs keeps climbing, from private firms and municipal authorities alike, drawn by the sheer range of returns — smaller sums paid out for cooling, a lower threat of flooding, fresh habitat for urban wildlife, cleaner air, and even the chance to raise crops several storeys up. Faced with competition for resources and shrinking open land, cities turn to such bold designs to adapt. What settles their success is not the technology alone but the readiness of councils, companies and other bodies to take part, backed by study of which solutions suit a city's varied roofs. Increasingly, planners also design green roofs to work alongside other environmentally minded features — 'living walls' clad in vegetation over soil or water, and street-level drainage such as lines of trees — so that rainfall is managed better and the built landscape grows more sustainable. Ireland came late to all this, and its local authorities are largely the ones driving it along; Dublin, where a far-sighted measure called the City Canopy Scheme has more than doubled the green-roof area, holds much of the national market.
B
BBeyond these practical gains, a steadily widening body of study is drawing attention to what green roofs do for people directly. Physicians now quite frequently write out prescriptions for time spent gardening in the fresh air, reaching for it as a way of supporting patients who are wrestling with anxiety or low spirits. Investigators have found, too, that contact with even the plainest scrap of greenery can lift the day-to-day quality of life of those living with dementia, and can leave a person less likely to go on to develop diabetes. Discoveries of this kind are gradually strengthening the argument that a rooftop need be neither large nor elaborate to be worth planting.
C
CIn Australia and New Zealand, by contrast, planted roofs slipped into the mainstream long ago, and large, publicly accessible and crop-bearing examples now sit atop buildings across both countries. Once again it has fallen to mayors and civic authorities to push things along: Sydney only lately obliged every new building to carry a green roof, whereas Wellington's encouragement of rooftop farming reaches back to schemes drawn up in the 1990s. A further edge is their young building stock, which makes fitting a roof simpler. Holding enough water up at roof level, and spreading it evenly across the surface, is what keeps the planting alive — the demands running highest on the 'edible' roofs given over to fruit and vegetables. This is far easier on recent structures, generally built to bear heavier loads, than on an older one adapted afterwards; and since a sturdier roof takes a deeper layer of soil, it also allows a wider assortment of plants. What has worked in these cities, many argue, ought to serve as a template elsewhere.
D
DIf green roofs are ever to become routine on new developments, backing from the public sector and from private investors alike will be indispensable. Those charged with looking after a building may find they have to take on unfamiliar skills, landscaping among them, and here and there a team of volunteers might be called on to lend a hand. Yet when the point comes to win over investors and developers, it is the economic reasoning that still counts for most, and a convincing financial case has to be set out before any of them will commit. A phrase has even been minted for the purpose — 'natural capital' — to pin down the monetary worth of the natural world: the savings, say, that follow from picking natural defences against flood damage, from adjusting to a shifting climate, or from helping people lead healthier and more contented lives.
E
EAs shared know-how has deepened, formal standards have taken shape to guarantee that green roofs are properly designed, built and cared for. Advances in the underlying science have meanwhile spawned fresh takes on the idea. 'Blue roofs' let a building cling to water over longer stretches rather than shedding it at once, which matters when downpours turn heavier; there are pairings of planted roofs with solar panels, whose purpose is to draw power from a renewable source; and 'brown roofs', left deliberately wilder, set out to give a home to as many kinds of wildlife as they can. None of it comes free of complication, however. Before a single roof goes in, a run of hurdles must be cleared — laying drainage routes, meeting health-and-safety rules, at times arranging public access, and living with planning limits and the upheaval that building work brings to a structure and its surroundings. Clear these, and the trend could bring new jobs and a livelier local food economy; the evidence so far hints that such roofs might remake our cities and keep them working sustainably for years to come.
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Question 1 - 5
Which paragraph contains the following information?
A
B
C
D
E
1.
a set of practical obstacles that must be settled before installing a green roof
2.
mention of somewhere that has backed rooftop greenery over a long period
3.
the view that schemes already in place should guide future projects
4.
examples of green roofs being combined with a city's other eco-friendly installations
5.
the point that a strong economic argument has to be made in order to secure support