Modern civilisations thrive in cities and with about 20 people every minute who are migrating to cities, it may indeed be more accurate in the Indian context.
Every year, in the month of April the concrete jungles, that are our cities, start simmering in heat, bringing discomfort to citizens. Over the next few months, top headlines in media are related to rising heat and its ramifications like widespread cases of heat strokes, electricity cuts, depleted water tables and general discomfort. By 2050, India is likely to see 85-90 crore people living in urban spaces. We are looking at a future where Urban Heat Island (UHI) phenomenon is going to expand and quality of life is going to suffer for the city dwellers.
There is a pressing need to include the Urban Green Space (UGS) or the ‘green oasis’ in urban landscape planning. As per research done in the European context, during daytime in summer, cities can be up to 12°C hotter than rural areas and for each 1°C rise in temperature, the risk of death increases by between 1% and 3%. Heat exposure also increases the risk of suffering cardiovascular and respiratory illnesses. The urban surface of concrete, asphalt & stone has higher thermal capacity and low albedo/reflectance, which absorbs short wave radiation from solar spectrum during day and releases long-wave radiation at night, resulting in higher night time temperatures in urban areas compared to rural areas. This in turn increases the electricity requirement for cooling and also traps atmospheric pollutants contributing to increased smog and associated health issues.
The state of Tamil Nadu recently declared heatwave as a state emergency. Not only this, but the state has been a leader in planning sustainable development models centred around natural resources conservation. It’s time for other states to follow the lead and plan urban and peri-urban green spaces diligently.
Though Tier II and Tier III cities are catching up fast in terms of public amenities, the lack of job opportunities and access to higher education are still fuelling migration to urban areas; hence UGSs are vital as they provide ecosystem services like temperature regulation, carbon sequestration, storm-water retention, ground water recharge and recreation.
The US Public Health Bureau prescribes the minimum international standard for urban greenspace per capita as 18sqm, while the World Health Organisation standard for urban greenspace is nine sqm per capita. In the Indian context, the Urban and Regional Development Plans Formulation and Implementation (URDPFI) prescribes a minimum of 10 sqm per capita of UGS, which is met only two Indian cities, Jammu & Noida while it has drastically decreased for cities like Jaipur, Chandigarh and Lucknow.
Old Greek and Roman towns as well as Mughal town planning had a component of dedicated open, green spaces for public as well as private spaces for rulers. The European Commission has acknowledged intrinsic value of UGS for its ecological functions and relevance to societal well-being. The UHI effect is a significant environmental issue impacting air quality, thermal comfort, energy consumption & well-being of people, especially vulnerable sections like children and senior citizens.
In India, the most followed document for city planning is the URDPFI but its focus is primarily limited to recreational spaces. Given the variation of surface and air temperatures in different types of urban area structures due to geographical diversity of Indian cities, it is imperative to objectively quantifying greenspace requirements so that Land Surface Temperature (LST) may be mitigated for large cities. This would help mitigate temperature differences between urban and neighbouring rural areas.
Urban greening efforts from green roofs to courtyard scale to large parks and city forests may create porous surface for airflow, allow heat sink, evapotranspiration and can reduce UHI formation and micro-climate regulation. As per literature available, a row of trees and green patches in parking lots may bring down the temperatures to a maximum of 7.26 degrees. In terms of cooling effect, trees have strongest impact followed by bushes and grassland fields. In addition, with global warming and an expanding summer season, having green spaces or parks nearby urban areas for children and elderly to walk, run, do yoga and meditation may go a long way in reducing the looming public health expenditure.
Recent studies have developed models for various cities based on various geographic factors, anthropogenic factors like population, buildings structures, density of roads and water bodies to prescribe UGS for particular city, as they are the most economical antidote to the Heat Islands that modern cities are.
As per the research done in Department of Architecture & Planning in MNIT, Jaipur for the four cities of hot state of Rajasthan, a model was developed which concluded an additional UGS requirement of 15.7 ha for Sikar city, 8.4 ha for Churu city, 18.23 Ha for Sri ganga Nagar city with suggestion for suitable areas for Green Spaces Development so mitigate the UHI effects. Apart from the availability of land, the most crucial factor is water availability and its quality determines the kind of vegetation that’s most suited for that place at least ecological costs possible.
Savita Dahiya is deputy conservator of forests & member secretary, district environment committee, Barmer-Balotra, Rajasthan.