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Biodiversity is the variety of life in a certain area- the range of plants, animals and other organisms that can be found in one ecosystem. For many people, biodiversity is something that is associated with rural areas, where you can see the various species of plants and animals alive and thriving. It’s important to remember that biodiversity also exists in cities and other urban areas, and perhaps the reason we don’t notice biodiversity so easily in these places is because we need to help it flourish. But how do we do that? In recent years, many buildings have added green roofs and living walls to their facades. These features create cleaner air, introduce new plants into the local ecosystem, and provide a habitat for other creatures. They also improve the appearance of the buildings they live on and don’t take up as much space as traditional green spaces such as trees or parks. Increasing the biodiversity of urban areas has meant finding creative solutions, like green roofs and living walls, to the lack of free space in urban areas.

For thousands of years, humans have formed large communities that have grown to become cities, so the urban environment is nothing new. What is new, however, is the huge amounts of concrete, roads, and cars that can now be found in every city. With the increase of non-natural materials and carbon emissions, it can be difficult for local plants and animals to thrive. Biodiversity is often used as a means of measuring how healthy a particular ecosystem is; a healthy ecosystem will be able to sustain a wide variety of life. A lack of biodiversity in an area can lead scientists studying it to notice problems like unclean water or air pollution. The term “biodiversity” (short for “biological diversity”) was first used in the 1980s when discussing nature conservation, as the world realised that we need to conserve nature in order to protect the environment. Nature conservation has become more even important in the 21st century, and biodiversity is now used as a means of measuring the health of an urban environment, as well as rural environments. 51% of the world’s population now live in cities, creating a huge carbon footprint. One way to offset this carbon footprint is to promote a healthy environment by encouraging its biodiversity. In urban areas where the human population has changed the landscape, green initiatives need to be put in place to help the other local populations survive. Living walls are a great example of this as they introduce plants to the environment and can house a variety of living creatures such as birds and insects. When installing a living wall, a conscious effort is always made to ensure that the plants in the wall are locally found species and do not harm the local ecosystem. For example, in the UK, Viritopia runs a post code-specific green roof service. This means that the choice of soil, grasses and flowers planted in each green roof or living wall are matched to what naturally grows nearby. Matching this new plant life to its surroundings means that the local wildlife will be able to eat it and live in it. Using local plant species in green features also ensures that the living walls and green roofs will thrive, as the plants they contain have been proven to grow well in the local climate.

The City Biodiversity Index (also known as the Singapore Index) is an index created in 2008 that is used by cities around the world such as Montreal, Lisbon, and Helsinki, to measure their biodiversity. The Index works on a scoring system, and a city can score up to 92 points based on how well it matches the index’s criteria. To use the index, a city checks its environment against the index’s core components: native biodiversity in the city, ecosystem services, and governance and management of biodiversity. There are indicators within each of these core components such as “proportion of protected natural areas”, “regulation of quantity of water”, and “budget allocated to biodiversity”. Each indicator can score a maximum of four points. The city measures itself against the index on an annual basis, using its first year’s results as a baseline from which they can compare and, if necessary, improve. As more cities have adopted this index, there has also been a rise in living walls around the world.  This is because the CBI has shown city planners that more work needs to be done to help local biodiversity, yet previous building means that natural habitats must fit in to the urban environment. With little space for parks or trees, living walls and green roofs are a great alternative that can add to the area’s biodiversity.

Multi-storey office buildings and large apartment blocks are common reminders of the lack of available space in cities around the world. The iconic skylines of the world’s most famous cities came out of a necessity to fit as much as possible into a smaller space. A lot of research about the biodiversity of cities has taken place after these cities were filled so a new issue was created- how do we promote biodiversity with no land? In the ‘80s and ‘90s, green roofs and living walls began to be produced and by the 21st century, they had become fixtures in cities across the globe. Green roofs and living walls cover space that has already been taken up by buildings, adding to their beauty and biodiversity. Numerous cities are now calling for green features like these in all future building plans, as the benefits they provide to local biodiversity have been clear. A city’s ecosystem supports a far denser population than any rural area- living walls and green roofs are essential to helping that ecosystem to sustain all forms of life when faced with limited space and air pollution. In the bustle of city life, it can be easy to not notice the wildlife that shares the ecosystem but thanks to features like green roofs and living walls, everything in a city can co-exist in a healthy way.

Green roofs are a type of natural flood management.  In urban areas roofs make up large areas of hard standing and runoff can be huge. The plants on a green roof use up a small amount of water, however the substrate (soil) beneath them will soak up a significant amount of water.  The saturated soil will slowly release water off the roof, but the green roof slows the process down reducing the risk of a flash flood. A green roof can retain around 75% of the runoff in summer (source: livingroofs.org).  Green roofs alone would not prevent flooding. However as part of a wider rainwater management scheme they can be a useful contribution.

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