Urban inequalities and heat risks in Delhi

The sixth assessment report by the United Nation's Inter-governmental Panel on Climate Change released this week has issued dire warnings that have major implications for India. Warming over India is projected to track the global average and the nation is expected to see an increase in frequency and severity of hot extremes.

As population and urbanisation, built up areas and concretisation expands in Indian cities, vulnerable populations will increasingly be exposed to high levels of heat. No where is this more obvious than in the city of Delhi, India’s capital and second largest city by population, where temperatures are known to rise beyond 44⁰C.

Heat in Delhi is known to have a spatial distribution and is more in certain areas as compared to other. This is because some areas in the city are extremely crowded, continue to be devoid of spaces and vegetation, while the central and eastern parts of Delhi are green and have riverine areas while the northern and western peripheries have agricultural activity, which provide those who live nearby protection against the heat.

What could be the climate justice implications of urban heat and greenspace distribution for the socially vulnerable groups in Delhi? The study aims at exploring the implications of the spatial distribution of urban heat and greenspace in May (pre-monsoon) on socially vulnerable groups in Delhi and the impact of seasonal variations in temperature on heat distribution.

Delhi, a fast growing urban space

Delhi is projected to become the largest urban agglomeration in the world by 2030 and has the highest population density of any state or union territory of India according to the 2011 census. Twenty seven percent of the population in the state is 14 years old or under, while  98 percent of the population of NCT is classified as urban, with 78 percent of the land area being classified as urban.

The southwest and northwest districts that correspond to Najafgarh and Narela zones are the relatively rural parts of Delhi. In 2011 however, 94 percent of these two districts were classified as urban. Majority of the population in the city lives in unauthorised or regularised slums or colonies (65 percent), a small proportion live in rural and urban villages (12 percent), while only 24 percent live in planned colonies with assured access to infrastructural services according to the year 2000 figures.

Heat exposure in the study was estimated using the urban heat risk index (UHRI) that included biophysical factors related to urban heat. NDBI (normalised difference built-up index) measured impervious surface coverage, while vegetation abundance, indicative of greenspace, was assessed by calculating the NDVI (normalised difference vegetation index)'

Urban heat areas in the city

The study found that the city has a heterogeneous distribution of heat areas based on presence and absence of vegetation. For example, parts of Delhi that contain agricultural flood plains and parklands along the Yamuna river on the eastern margin show lower heat exposure and higher levels of vegetation. This area also has a high population of economically and socially marginalised sections that reside on the banks of the river and depend on the river for their livelihoods. Parallel to the Yamuna and to its west is the Delhi Ridge, a partially deforested area that remains a considerable greenspace within Delhi and serves as residential and leisure space for affluent residents.

Delhi’s agricultural areas in its north and west also experience variable exposure to heat and greenspace. In pre-monsoon May, these areas get exposed to very high heat and the western-most wards have very high heat levels  in September compared to the rest of Delhi. However, in the post-monsoon period, these areas have considerable green areas that are similar to that in the Yamuna and Ridge areas. These variations in pre-monsoon and post-monsoon greenspace result in differential heat exposure, which has different impacts on the populations that reside in these areas.

Socioeconomically vulnerable are more exposed to urban heat risks

With respect to the urban heat risk (UHRI) in May, the hottest month of the year, wards with several vulnerable groups such as children, agricultural workers, and larger sized households are at the higher risk of heat exposure. Households with fewer resources or reduced capacity to mitigate heat-related risks (e.g., via home air-conditioning) face disproportionately higher heat exposure. Although temperatures and UHRI values decline after the monsoon, wards with a higher proportion of children and lower proportion of households with assets continue to face higher heat exposure.

With regard to pre-monsoon vegetation, vulnerable groups such as children, agricultural workers, and large size households that face higher heat exposure are found to reside in areas that have no green space. In contrast, economically affluent households with assets and electricity that have lower heat exposure in May are found to reside in wards with higher greenspace.

Climate change induced urban heat will disproportionately impact households that lack assets and electricity. It is thus important to identify those who need assistance to mitigate heat stress at the policy level and devise strategies to help these vulnerable populations.

More focus on peripheral and vulnerable populations such as poor households and women and children, expansion of greenspaces  and improved access to electricity among the vulnerable populations can go a long way in coping with the effects of rising heat in the city in the years to come, argues the paper.