More than 50% of the population lives now in cities, this number is expected to rise to two thirds by the year of 2050 according to UN-Habitat project. Cities has an important role in the recognition of sustainable development since the majority of the world’s economic activity is concentrate in urban areas. Each city designs its spaces, buildings and infrastructures in a certain pattern that shapes its urban life and its economic activities. These patterns that the developing cities follow affects the world’s economies, energy use and climate change. Developing green economies at the city scale requires the implementation of sustainable patterns for urban development and supportive city planning. New approaches is essential to be integrated in the urbanization process.
One of the significant approaches that a city can adapt to develop green economies is to create patterns in its land that can provide large green patches and more sustainable urban development. Landscape ecologies always search and analyze the patterns that can give optimal results for both people and natural systems. Richard Forman explained in his book “Land Mosaic”1995 landscape ecologies principles. He stated the two patterns of the urban growth that results favorable sustainable approach.
The ‘satellite cities’ and ‘compact concentric zone’ models of development are the patterns that gives an optimal result. Generally these patterns has a greater number of large patches and areas of green spaces for ecosystems.
Satellite cities is an approach that is being adapted in many developing cites to build a sustainable landscape ecology. In India, the government agreed to develop 35 new satellite townships that will have approximately million – plus population along Gurgaon and Noida. The plan of the city is to provide the accommodation of at least 40% of India’s population in 2012 in Urban India. The intention of implementing such a pattern is to create cities with adequate economic actives that are linked to the major cities around them forming a continuous participation of urban development and activities.
The other pattern explored by Richard Forman that can attain also an optimal result of green urban development, ‘compact concentric zone’, represents a model in which the city is divided in a set of concentric circles expanding from the downtown to the suburbs. Transportation routes and a hierarchy of nodes connects the population center. This model is presented by Burgess in 1925, it was formed from his observations of a number of Americas Cities.
Other patterns of urban growth that leads to less optimal results is the urban sprawl. Urban sprawls represents the spatial expansion of the urbanized areas of a city through time. This model frequently creates communities with heavy automobile usage resulting GHG emissions and infrastructure costs. It is one of the least attractive designs because it conserve fewer patches of land for ecosystems. It mainly occurs in wealthy market economies with rapid population growth where rich people tend to move to big lots on the outskirts of the cities and they will travel by car every day. This will cause environmental and economic drawbacks for city. It will cause extreme traffic in the main transportation nodes and in some cases like the city of Cairo, the settlements resulting from the urban sprawl is disturbing the agriculture land. At present 81 percent of informal units in Greater Cairo sit on privately owned agricultural land. Since 1982 the Government has sought to redirect urban growth out of the Nile Valley into satellite commu¬nities on the adjacent desert area. To this end the Government has prohibited the conversion of private agricultural land to urban uses while investing heavily in housing and infrastructure in desert areas. These measures have been partly success¬ful in meeting goals. Between 1995 and 2007, for example, developers urbanized 110 km2 of desert land, but at the same time 55 km2 of dwindling agri¬cultural lands were urbanized as well. Furthermore, development on desert land brings its own share of challenges, including the sustainable provision of potable water. (UN-Habitat 2010c).
Another pattern that creates undesirable economic activities is the uncontrolled development along transportation corridors. This pattern is very common in all the world, it contributes to a high number of traffic fatalities that arises every year, and most of them take place in low-and middle income countries. This kind of pattern disturbs the natural ecology of land, such as the waterway and it also increases the risk of natural disasters such as the landslides and floods.
Selecting a pattern that will be the ground in which the urban growth will follow is very vital to achieve a sustainable economic. Fortunately, with proper urban planning we can preserve the ecosystem and create a sustainable development while accommodating population and economic growth.
Another pattern that can be adapted to achieve a sustainable economy is the development of compact cities and preplanned extensions of urban areas. This approach provides relatively high residential density with mixed land uses. It is established on an efficient public transport system and has an urban layout which encourages walking and cycling, low energy consumption and reduced pollution. Compact cities also encourages the input sharing and knowledge spillovers. Besides that compact cities yield economic savings in constructing and operating infrastructure and in the urban services. In addition that, compact cities has a lower consumption of energy and emission of greenhouse gases compared to sprawling cities.One of the reason for this difference is the amount of traffic distance in the sprawling cities.
To obtain a sustainable development it is preferred that the growth of the compact cities happens around the public transportation network to minimize the emission of greenhouse gases and to reduce the use of private vehicles.
Significant challenges remain to achiev¬ing green economic development in the cities, including, firstly, a set of hurdles related to governance. Few sub-national authorities correspond to the natural economic boundaries of a city. Within an urban region, officials may establish specialized agencies either to address a specific environmental issue such as air pollution or to promote economic development. If cities are to continue to benefit from agglomeration advantages in the face of planetary crises, it is the responsibility of all city stakeholders to work together to pursue these goals as a matter of urgency.
http://mirror.unhabitat.org/documents/SOAC10/SOAC-PR1-en.pdf
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