段落A

Rooftops covered with grass, vegetable gardens and lush foliage are now a common sight in many cities around the world. More and more private companies and city authorities are investing in green roofs, drawn to their wide-ranging benefits. Among the benefits are saving on energy costs, mitigating the risk of floods, making habitats for urban wildlife, tackling air pollution and even growing food. These increasingly radical urban designs can help cities adapt to the monumental problems they face, such as access to resources and a lack of green space due to development. But the involvement of city authorities, businesses and other institutions is crucial to ensuring their success – as is research investigating different options to suit the variety of rooftop spaces found in cities. The UK is relatively new to developing green roofs, and local governments and institutions are playing a major role in spreading the practice. London is home to much of the UK’s green roof market, mainly due to forward-thinking policies such as the London Plan, which has paved the way to more than doubling the area of green roofs in the capital.

段落B

Ongoing research is showcasing how green roofs in cities can integrate with ‘living walls’: environmentally friendly walls which are partially or completely covered with greenery, including a growing medium, such as soil or water. Research also indicates that green roofs can be integrated with drainage systems on the ground, such as street trees, so that the water is managed better and the built environment is made more sustainable.  There is also evidence to demonstrate the social value of green roofs. Doctors are increasingly prescribing time spent gardening outdoors for patients dealing with anxiety and depression. And research has found that access to even the most basic green spaces can provide a better quality of life for dementia sufferers and help people avoid obesity.

段落C

North America, green roofs have become mainstream, with a wide array of expansive, accessible and food-producing roofs installed in buildings. Again, city leaders and authorities have helped push the movement forward – only recently, San Francisco, USA, created a policy requiring new buildings to have green roofs. Toronto, Canada, has policies dating from the 1990s, encouraging the development of urban farms on rooftops. These countries also benefit from having newer buildings than in many parts of the world, which makes it easier to install green roofs. Being able to keep enough water at roof height and distribute it right across the rooftop is crucial to maintaining the plants on any green roof – especially on ‘edible roofs’ where fruit and vegetables are farmed. And it’s much easier to do this in newer buildings, which can typically hold greater weight, than to retro-fit old ones. Having a stronger roof also makes it easier to grow a greater variety of plants, since the soil can be deeper.

段落D

For green roofs to become the norm for new developments, there needs to be support from public authorities and private investors. Those responsible for maintaining buildings may have to acquire new skills, such as landscaping, and in some cases, volunteers may be needed to help out. Other considerations include installing drainage paths, meeting health and safety requirements and perhaps allowing access for the public, as well as planning restrictions and disruption from regular activities in and around the buildings during installation. To convince investors and developers that installing green roofs is worthwhile, economic arguments are still the most important. The term ‘natural capital’ has been developed to explain the economic value of nature; for example, measuring the money saved by installing natural solutions to protect against flood damage, adapt to climate change or help people lead healthier and happier lives.

段落E

As the expertise about green roofs grows, official standards have been developed to ensure that they are designed, constructed and maintained properly, and function well. Improvements in the science and technology underpinning green roof development have also led to new variations in the concept. For example, ‘blue roofs’ enable buildings to hold water over longer periods of time, rather than draining it away quickly – crucial in times of heavier rainfall. There are also combinations of green roofs with solar panels, and ‘brown roofs’ which are wilder in nature and maximise biodiversity. If the trend continues, it could create new jobs and a more vibrant and sustainable local food economy – alongside many other benefits. There are still barriers to overcome, but the evidence so far indicates that green roofs have the potential to transform cities and help them function sustainably long into the future. The success stories need to be studied and replicated elsewhere, to make green, blue, brown and food-producing roofs the norm in cities around the world.

    草坪、菜园和茂密的植被覆盖的屋顶在当今许多城市已经不再罕见。越来越多的城市政府和企业被绿色屋顶所吸引，并开始投资该项目。这些绿色屋顶带来了许多好处，如降低能源消耗、减少洪水风险、为城市野生动植物提供栖息地、解决空气污染问题，甚至可以种植食物等。这些创新城市设计有助于解决城市面临的重大问题，如资源获取和因城市发展而缺乏绿地。然而，要实现绿色屋顶的成功，城市政府、企业和其他机构的参与至关重要。同时，我们需要对适用于城市不同屋顶的各种选项进行深入研究。目前，英国在绿色屋顶的发展方面仍处于初级阶段。地方政府和机构在推广这一实践方面发挥着重要作用。伦敦是英国绿色屋顶的中心，这主要得益于其开拓性的政策，如《伦敦计划》。该计划使伦敦的绿色屋顶面积增加了一倍以上。

不断进行的研究揭示了城市中绿色屋顶与“活墙”的结合方式：这些环保墙壁部分或全部被覆盖着绿色植物，包括土壤和水等生长介质。研究还表明，绿色屋顶可以与地面上的排水系统（如街道树木）相结合，更好地管理水资源，使建筑环境更可持续。此外，还有证据表明绿色屋顶具有社会价值。医生们越来越多地为焦虑和抑郁症患者开具园艺处方，鼓励他们在户外花时间。研究还发现，即使是最基本的绿色空间也能提高老年痴呆症患者的生活质量，并帮助人们避免肥胖问题。

在北美地区，绿色屋顶已成为主流，建筑物上安装了各种广阔、易于进入且可供食用的屋顶。此外，城市领导和政府一直在推动该运动的发展。不久前，美国旧金山市制定了一项政策，要求新建筑物必须有绿色屋顶。加拿大多伦多从上世纪90年代开始出台政策，鼓励在屋顶上发展城市农场。这些国家还因拥有比其他地区更新的建筑物而受益，这使得安装绿色屋顶变得更加容易。在维护绿色屋顶上的植物方面，保持足够的水分并均匀分布至关重要，特别是在种植水果和蔬菜的“可食用屋顶”上。在更新的建筑物中，这样做要容易得多，因为它们通常可以承受更大的重量，而不像老旧建筑物需要进行改装。坚固的屋顶还有助于更容易种植更多种类的植物，因为土壤可以更深。

要使绿色屋顶成为新建筑物的常规选择，需要公共当局和私人投资者的支持。负责维护建筑物的人可能需要学习新技能，如园艺设计。在某些情况下，志愿者的帮助可能也是必要的。还需要考虑其他因素，如安装排水路径、满足卫生和安全要求，并可能需要向公众开放。此外，在安装期间可能会受到建筑物内外常规活动的限制和干扰，因此需要做好计划。为了让投资者和开发商相信安装绿色屋顶是值得的，经济依据仍然非常重要。术语“自然资本”已被提出，用于解释自然的经济价值；例如，我们可以计算通过采用自然解决方案来降低防洪损失、适应气候变化或改善人们的生活质量所带来的好处。

随着对绿色屋顶的专业知识不断增长，已经制定了官方标准，以确保它们得到正确设计、建造和维护，并能够正常运行。支持绿色屋顶发展的科学和技术进步也导致了新概念的出现。例如，“蓝色屋顶”可以储存水资源，并在较长时间内释放，而不是迅速排水。这在降雨较多的情况下非常重要。还有一些方案将绿色屋顶与太阳能电池板相结合。而“棕色屋顶”更贴近自然，最大程度地增加生物多样性。如果这种趋势持续下去，它可能会创造新的就业机会和更加充满活力和可持续的本地食品经济，同时带来许多其他好处。尽管还有一些障碍需要克服，但到目前为止的证据表明，绿色屋顶有潜力改变城市，并在未来帮助城市实现可持续发展。成功案例需要被研究并复制到其他地方，以使绿色、蓝色、棕色和生产食物的屋顶成为世界各地城市的常态。