Urban Green Spaces
AN ESSENTIAL ELEMENT IN CITY LIFE
Words: Francini van Staden
When somebody mentions ‘cities’, skyscrapers and concrete surfaces often come to mind, not luscious green spaces. However, after many years of being undervalued, a significant aspect of urban areas has sprouted and is growing steadily in built up areas: urban green spaces. The benefits of these green spaces cannot be underestimated and should be an essential part of city life.
Since 2007, the world’s cities were officially home to more people than their rural counterparts. But a look at the following figures illustrates a lopsided situation: cities only occupy 2% of the globe, yet cities and their inhabitants are responsible for gulping up over 75% of all natural resources. This is unsustainability at large! Fortunately, hidden within urban green spaces is the potential to correct this unsustainable situation and to provide a continuous cycle of ecological perks.
Urban green spaces
In its most basic form, the term ‘green space’ is an outdoor, un-built environment. Within this broad context, a variety of green spaces can be identified within the average city. While the ecologists define urban green spaces as ecosystems – environments that sustain communities of living organisms – the socialists define urban green spaces as publicly accessible spaces for society’s utilisation and enjoyment. These two urban green space definitions may seem totally different, but ideally enhance each other. Taking these different disciplines and explanations into account, urban green spaces can comprehensively be described as formal or informal and unofficial open vegetated spaces, fulfilling ecological functions and providing natural habitats, while serving society.
Commonly recognised urban green spaces include urban parks, greenways, squares and plazas, botanical gardens, recreational parks, memorial grounds and community open spaces. The less commonly recognised urban green spaces are within neighbourhoods, vacant plots and even less unofficial spaces boiling down to residential gardens or street trees. What is worth noting is that green spaces are not necessarily defined by their surface area occupied by vegetation, but rather the presence of vegetation. This allows areas not traditionally regarded as urban green spaces, to be considered urban green spaces as well!
Humanity is entirely dependent on the natural environment for its survival. Or to put it another way, it is the ecosystem services that provide for human life. This includes food, water, health and pharmaceutical benefits, genetic resources, fibre and timber, soil formation, pollination and resources for industrial processes as well as pollution control. Unfortunately, ecosystem services continue almost completely unnoticed by the majority of the global population, and are taken to be the norm of life on earth.
In focusing on urban green spaces, the following ecological or ecosystem services come into play:
- water resource and quality protection
- biodiversity and species protection
- storm and flood water control
- air purification
- natural resource conservation
Water resource & quality protection
Wetlands, whether natural or man-made, often form part of urban green spaces. Often described as ‘the kidneys of the natural environment’, the role of wetlands in water purification and resource protection is huge and extremely valuable. Urban water runoff collects all kinds of pollutants, from hydrocarbons to heavy metals. Instead of directing these pollutants to nearby rivers, urban green spaces containing wetlands capture the polluted water for temporary storage. Through complex filtering processes, pollutants and foreign chemicals are broken down into unharmful chemicals and nutrients that can be absorbed by the natural environment. Like human kidneys, wetlands purify water passing through the ecosystem, effectively reducing and even eliminating pollutants.
Biodiversity & species conservation
On a global scale, biodiversity (the variety and number of living species within ecosystems) is continuing to decline steadily, even rapidly, despite the fact that biodiversity protection is featured on every global environmental agenda. The continued loss of biodiversity is a major environmental concern and it should be one of our greatest environmental concerns. Why? Because the elimination of species and lowered biodiversity levels are directly related to the human ability, or inability rather, to survive on earth. Cities, urbanisation and land use change are the three culprits contributing to our rapid and somewhat uncontrolled downspiralling of biodiversity. However, urban green spaces can protect and enhance biodiversity and species extremely well. The mere increased vegetation cover due to urban green spaces contributes to increased biodiversity and conservation.
Storm & flood water control
With so much concrete in city areas, natural water absorption into soil is extremely limited. For instance, rain water has to be channelled through hardened surfaces which in turn results in increased flood risk, threatening properties and livelihoods. Flood water control and intervention is an ecological service associated with urban green spaces. This ecological service can go a long way to disseminate heavy rainfall and floods. A key characteristic of urban green spaces is the natural ground cover; this allows for the natural uptake of water, in addition to the fair share of water absorbed by plants. It is estimated that cities with a reasonable urban green space coverage, can naturally absorb up to two-thirds of stormwater, preventing flood hazards while recharging surface and groundwater. Without urban green spaces, none of these ecological services and processes can continue.
City traffic and industrial activities are two main sources of air pollution in cities. Urban green spaces play a major role in regulating and reducing air pollution within our cities. Air, including pollution particles, is taken up by plant foliage and while the pollution particles are captured within the foliage, purified oxygen is respired by the plant. The higher the level of plant coverage and foliage, the greater the air purification results. Research has shown that a striking 85% of air pollutants surrounding park areas can be cleansed through vegetation and trees and a street lined with trees reduces air pollution by up to 70%. The air filtering services offered by urban green spaces is no small feat – man can only match this through specialised and intensive technology.
Natural resource protection
No human life can exist without the support of natural resources. Yet it is because of this anthropogenic pressure that the environment’s natural resources: soil, water, air and living matter are threatened by pollution and exhaustion. However, urban green spaces offer functional benefits. Vegetation cover offers soil protection and erosion control benefits. For plant, animal, reptile and bird species, urban green spaces can act as a safe refuge. Sometimes, even higher biodiversity is noted within city borders than outside the city borders. The European Common Frog is one such example: the frog’s population numbers are higher within London’s urban open spaces, than in rural areas outside the city.
Urban green spaces also play a major role in reducing energy consumption, particularly during summer months. Have you noticed higher temperatures in city centres, in contrast to lowered temperatures outside the city? This is described as the ‘heat island effect’ and is the result of high percentages of concrete and tar in inner cities. The US Environmental Protection Agency recorded day time temperature increases of between 1–3ºC and night time increases of up to 12ºC for a city of one million citizens. Higher temperature increases the need for energy intensive cooling and air conditioning systems, however with abundant trees striking down the heat island effect, our demand for energy is reduced.
What’s happening in South Africa?
“On a global scale, biodiversity is continuing to decline steadily, even rapidly, despite the fact that biodiversity protection is featured on every global environmental agenda. The continued loss of biodiversity is a major environmental issue, and it should be one of our greatest environmental concerns.”
Johannesburg is reputed to house the largest urban man-made forest in the world. The city’s urban forest boasts with an impressive estimate of at least 10 million trees. The city is also home to over 22,000 hectares of urban green spaces within the city borders; including 2,343 city parks, 22 nature reserves, 15 bird sanctuaries and millions of trees lining the city’s streets. The city council places emphasis on utilising the city’s urban green spaces for lowering environmental impacts, conserving natural resources and environmental education. As far as the city’s formal urban green spaces are concerned, this strategic planning seems to be delivering results. However, there are constraints and difficulties with informal green spaces. Informal urban green spaces are usually outside of the city’s budget for management. And where private landowners are involved, a lack of interest in open space management is another major constraint. These two major constraints are imminent in the level of disturbance, dumping and pollution noted for informal urban open spaces – and this is hampering the effective and beneficial functioning of the city’s informal urban green spaces.
On the homefront, the city of Cape Town is home to over 5,000 hectares of formal urban green spaces. There is the historically important Company’s Garden, the City Bowl’s tree sheltered De Waal Park, and the river, wetland and estuary Zandvlei Recreational Park. Two more urban green spaces in Cape Town deserve a special mentioned: the Green Point Urban Park and the Khayelitsha Wetland Park.
Green Point Urban Park is the new kid on the block. Formally opened in 2011, this multipurpose park focuses on combing city dweller recreation and biodiversity protection. In recognising the neglect of this ecologically important space, the City of Cape Town council embarked on an impressive mission to revive this 12 hectare space to an ecological and recreational lung, breathing steady for sustainable city living.
Described as the green heart of Khayelitsha, the 44,5ha Khayelitsha Wetlands Park has formal protected status. The Khayelitsha Wetlands Park must be one of the best examples of how urban green spaces can be incorporated even in the most overcrowded and lower income corners of a city. The wetland nature of this urban park means water purification possibilities and it is reported that the wetland system is fulfilling an ecological role to some extent. However, the wetland system and its water purification possibilities are stretched to the brim – the ecological functioning of the park is severely barred by pollution. The park is notably polluted from sources outside of Khayelitsha, but also from within the township. But the environmental urgency is prevailing and the city council is implementing a number of monitoring programmes with the help of local stakeholders.
When it comes to South African cities and conservation, the city of Cape Town is more prominent than all other South African cities. This is because the city falls within the Cape Region biodiversity hotspot – meaning the region’s biodiversity is remarkably rich in global terms. For biodiversity hotspots, environmental impacts and threats can be acute. It is because of this that the City of Cape Town council recognises Cape Town as one of the world’s key environmentally rich cities – the task of urban green space management is therefore at the forefront of the city’s planning.
As in the case of Johannesburg’s green urban spaces, Cape Town’s formal urban green spaces are reaching a notable extent of its ecological potential but development pressure is threatening to strangle the city’s informal urban green spaces. And although the City of Cape Town’s well-developed environmental and open space management planning offers confidence, a great and green onus remains on the shoulders of the private landowner: will you allow your informal urban green space to humbly continue its ecological services?
Are you opting for a green city?
The 20th century conservation giant, Aldo Leopold, recognised the importance of not limiting conservation efforts to wild lands – this alone is not sufficient to ensure long-term environmental conservation. In an unpublished manuscript dated 1948, Leopold said ‘What more substantial service to conservation than to practice it on one’s own land?’ And this is exactly where urban green spaces should supplement conservation, and how we, the average city dweller, can give back. The common thought is that cities are distinctly removed from nature, and are not able to contribute to environmental protection and biodiversity conservation. But this simply isn’t the case. At present, our globally fierce attempts to protect the environment and biodiversity are in desperate need of new forms of protection. Is it not time we change our thoughts about our living spaces, our cities, and start to believe that our cities can truly contribute to environmental protection? Every green spot in the urban environment contributes to a myriad of ecological services. Can we afford to continue with the traditional conservation outlook that does not recognise, let alone prioritise urban green spaces?
Our global reality is this: the majority of the world population lives in urban areas and our environmental protection actions are still largely deficient, causing the environment to remain extremely vulnerable. We have evidence that urban green spaces can contribute to positive environmental change so there is only one thing to do – make your city part of the change!
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