Earth Day is observed on April 22 to mitigate climate change, promote adaptation and improve public health.
The first Earth Day was held in 1970 with an aim to promote the thoughts of ecology, reverence for existence on earth and highlighting growing concern over pollution of the soil, air and water. The April 22 date was also designated as International Mother Earth Day by a resolution adopted by the United Nations in 2009.
Mother Earth is a common expression for the planet Earth in a number of countries and regions, which reflects the interdependence among human beings and other living species and the planet. This year's Earth Day theme is chosen as "The Face of Climate Change" by the Earth Day Network.
With more than half the world's population now living in urban areas, there are concerns that urbanisation is a key driver of unsustainable resource demands. Urbanisation also appears to contribute to the ever-growing levels of greenhouse gas (GHG) emissions and climate change. Climate change presents unique challenges for urban areas and their growing populations. Where urban areas grow rapidly without regard to current and future resource demands and climate change, large numbers of people and their assets can find themselves vulnerable to a range of disruptive and damaging risks.
Urbanism is a way of life and the outcome of urbanisation. It is the characteristic way of interaction of inhabitants of towns and cities with the built environment or, in other words, the character of urban life, organisation, problems, etc., as well as the study of that character or of the physical needs of urban societies or city planning.
Urbanism is a complex system of partial public and private realms that exist between buildings. Therefore, large cities are not the only examples of urbanism. It can exist in the smallest town too. First, it is in our homes and neighbourhoods that we generate the demand for the world's resources. Here, we eat most of our food, do much of our transportation, buy, use and dispose of most of the world's end products. Here, we use much of the world's energy for heating and cooling, lighting and operating appliances. Next to our buildings, including homes, shops and offices, we consume roughly half of the resources that contribute to climate change, in the activities like heating and cooling and running lights and appliances that are likely to trigger release of greenhouse gases somewhere else.
So, the shape of buildings, their efficiency of layout, their exposure to heat, their tendency to gain heat energy and their ability to accommodate our various habits of consumption, all have a significant effect on energy use and carbon emissions. So, clearly, the built environment has a major role in generating the causes of climate change and other unsustainable practices. Urban form is a critical aspect of the challenge of sustainability. "Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs," defined by the Brundtland Commission (formally known as the World Commission on Environment and Development), a panel convened by the United Nations in 1983. It contains the concept of 'needs', in particular the essential needs of the world's poor and the idea of limitations imposed by the state of technology and social organisation on the environment's ability to meet present and future needs. This means that when designing for sustainability, we must move beyond the scale of the building and design for sustainable urbanism. This is because urbanisation produces a warmer city centre compared to the neighbouring surroundings. The temperature in urban area could be 5-10oC warmer compared to rural areas. The effect is known as the Urban Heat Island (UHI) and is seen almost at all the big cities.
In an urban area, tall buildings, bridges and flyovers retard the free flow of air; so, suspended pollutants are not effectively removed. lack of open ground leads to less infiltration of rainwater in the ground as the tar roads and cement pavements are impervious to the percolation of rainwater. This increased runoff which leads greater risks of floods/waterlogging. The urban development very often takes place in a manner in which buildings and roads occupy the flood plains of the rivers and streams. This causes high runoffs/stagnation of water which cannot find its natural exit due to blocking.
Human activities produce 'greenhouse gases' into the atmosphere and they tend to trap heat in the Earth's atmosphere. Among the gases are carbon dioxide, methane and various other hydrocarbon compounds. However, there are a number of important things that can be done at the building scale, particularly when it comes to heating, cooling and lighting, which account for a large portion of energy consumed by the built environment. Building energy systems must be as efficient as possible while remaining reliable over time and with changing conditions. The efficiency of characteristic building types is closely connected to the efficiency of urban pattern. Again, the size, shape and orientation of an individual building are closely related to the size, shape and orientation of the neighbourhood itself. The characteristic buildings that are likely to be built in a neighbourhood are in turn related to the neighbourhood's connectivity, density, characteristic appeal and other factors. The building characteristics include, attached types, which tend to save heat from common walls; building orientation to take maximum advantage of passive solar exposures; buildings that are well-sheltered from the negative effects of sun and wind; buildings that line the street and support an attractive streetscape, conducive to pedestrian activity. Urban macro-effects are effects that are created by the urban pattern itself. They include Albedo effect, which is the tendency of buildings and paved surfaces to convert solar energy to heat energy and increases the greenhouse effect. This adds to the heating of cities. Heat island effect has the tendency of air to become trapped between buildings, especially tall ones, and heated above ambient levels. Again, this increases the heating of cities and can exacerbate heat wave effects. There are also some negative effects of tall buildings. These include wind effects, shadowing, and "canyon effect". So, the more we live in a neighbourhood with optimally distributed services, the more we are likely to use a more efficient combination of large and small facilities. We can live in a more efficient lifestyle, in a more efficient urban pattern over many years.
Therefore, urban form is a critical aspect of the challenge of sustainability. This means that while designing for sustainability, we must move beyond the scale of the building, and design for sustainable urbanism. For urban centres, this requires that they meet their resident's needs (being healthy, enjoyable, resilient places to live and work for all their inhabitants). Communities should be designed for the pedestrian and public transport. Cities should be shaped by physically-defined and universally-accessible public spaces and community institutions. Urban developments should be characterised by homes with front porches, sidewalks, retail development in close proximity to residential development, green public spaces and green corridors. Green corridors provide a rich habitat for a diversity of flora and fauna. A number of cities are developing this idea of green corridor as a tool both for protection of biodiversity and to provide a sense of continuity between town and country which can reduce climate-related risks.
Most urban buildings and infrastructure designed and built now would have to cope with climate change in future. As a result, it would be much easier to make provisions now for likely future climate-related risks in infrastructure expansion, new buildings and new urban developments than to have to retrofit buildings and readjust settlement layouts in the future. Built environment professionals must have a major role in making these reforms. The designers must take into account the factors at the scale of the building and factors at the scale of the neighbourhood and region for sustainable urbanism which would mitigate the climate change risks, promote adaptation and improve public health in future.
(Dr Mayarani Praharaj works at the Department of Architecture, College of Engineering and Technology, Bhubaneswar)