Urban Ecology and Global Climate Change. Группа авторов
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composition, thus, affecting CE (Richards et al. 2019). An extensive study was conducted by Wang et al. (2020) for 118 cities from 10 different biomes for observing the variation in CE. They used ordinary least squares (OLS) linear regression models with the percent of tree (Ptree) as independent variable and land surface temperature as dependent variable. They found the variation in CE from 0.04 to 0.57 °C with an average value of 0.17 °C where Ptree explained the 40.3% of the variation in the land surface temperature. Moreover, they observed that the biomes dominated by broadleaved trees reflect higher CE as compared to the biomes dominated by coniferous or sparse trees (e.g. savannas and shrublands). In addition to the inter‐city variations, intra‐city variations in CE were also observed, depending on the social and ecological contexts (Myint et al. 2015). Moreover, cities with hot and dry conditions (Mediterranean and desert biomes, e.g. Phoenix and Las Vegas) showed higher CE (Myint et al. 2015), whereas cities with hot and humid conditions (e.g. Nanjing, Beijing, Shenzhen, and Baltimore) reflected lower CE (Zhou et al. 2017). Exploring such scenarios for different cities from the developing and/or tropical nations could further help in mitigating UHI effects and adaptation to the climate change (Wang et al. 2020).
In addition to the direct reduction in land surface temperature, urban vegetation/tree shading also reduces the CO2 emissions from the buildings by cutting air‐conditioning costs during different weather conditions (Asgarian et al. 2015; Niemelä 2014). Moreover, visiting green space provides several benefits to the human in terms of health and well‐being; however, there is no conclusive research on the mechanism underlying such results (Wu 2013). Therefore, there is a need for interdisciplinary researchers including the sociologists, psychologists, public health practitioners, anthropologists, and the ecologists to explore the mechanisms behind the linkages between human health and green spaces (Tzoulas and Greening 2011). Further, planning and management of green spaces of an area have been influenced by several factors including from the personal/resident/owner level to the government and political levels which determine the type and size of vegetation (Niemelä 2014). Urban green spaces in cities are needed to plan in such a way that they can contribute to the climate change mitigation, by integrating and planting trees having optimal evapotranspiration potential and physical shading (Niemelä 2014; Vasishth 2015).
1.5.3.2 Green‐roofs
To mitigate the UHI effect, several measures have been applied and adapted in the urban areas. The examples include the use of heat‐reflecting surfaces and materials like sunward‐oriented roofs, roads and pavings, use of light‐coloured materials, increase in the proportions of vegetation to the hard landscapes, etc. (Vasishth 2015). In addition to these measures, adoption of roof‐top gardens or green‐roofs is the emerging field of research for reducing the UHI effect and mitigating the climatic change (Niemelä 2014). As like the functions of green spaces, green roofs also help in cooling by evapotranspiration mechanism. Earlier, green roofs were thought as the burden to the buildings, but now they have been gaining wider attention by the researchers as well as the urban residents as the additional protective covering to the roofs for protection from the heat stress (Vasishth 2015). Studies revealed that well‐designed and constructed green roofs may help in increasing the life of roofs and waterproofing structures even during the hot summer days (Vasishth 2015). However, research on exploring the ecosystem services to the humans (social and aesthetic benefits) provided by the green‐roofs still needs attention of the scientific communities (Jungels et al. 2013; Niemelä 2014).
1.5.3.3 Green Building
The built infrastructures utilise massive amount of resources and energy and produce substantial amount of waste products and GHGs emission as the output (Singh and Raghubanshi 2020). In this view, the U.S. Green Building Council's (USGBC) Leadership in Energy and Environmental Design (LEED) has launched a certification programme in 2000 with the aim ‘to develop and encourage green building expertise across the entire building industry’ (www.usgbc.org). The LEED programme is one of the key certification programmes for developing site‐specific building strategies and promoting the native plant diversity and water body conservation (Steiner 2014). This programme has four levels of certification, viz. certified, silver, gold, and platinum, depending on the credits received by a building project for six different categories which are: sustainable sites, water efficiency, indoor air quality, energy and atmosphere, innovation and the design process, and material and resources (Steiner 2014). Thus, the green buildings are the new initiatives launched by different agencies for the sustainable urban development and climate change adaptations. A few green building programmes viz. LEED India and the Green Rating for Integrated Habitat Assessment (GRIHA) in India are the two major certification programmes launched for regulating the infrastructure development and promoting sustainable building construction in India. Such programmes are working in congruence with the laws of the State and Central Governments of India (Singh and Raghubanshi 2020). Overall, researches on cost‐effectiveness of green buildings and the benefits arising from them need to be scrutinised further in different regions of the world in view of climate change mitigation.
1.5.3.4 Urban Water Bodies
Most of the urbanisations have taken place at or around the bank of rivers/streams or water bodies, globally. Most of the water bodies flowing/situating along/around the cities have been overexploited and suffering from challenges like high pollution load, improper planning, and management to the extreme events (e.g. floods), etc. (Verma et al. 2020b). Similarly, most of the cities are characterised by receding groundwater levels and high water tables due to imbalances in the utilisation and recharge of water from the aquifers (de Graaf et al. 2019). However, the role of water bodies in mitigating the impact of climate change and improving urban health cannot be ignored or compromised. The hydrological cycle of the urban ecosystems determines the overall habitat and vegetation composition (Verma et al. 2020b). The water bodies act as urban cooling island (UCI) which played considerable role in mitigating UHI effect (Yu et al. 2017; Yang et al. 2020). For example, water bodies having square or circular shapes are more effective in providing the UCI effect as compared to water bodies with irregular or complicated shapes (Du et al. 2016). Thus, there is an urgent need to develop and design policies for urban water body management. This can be done by using a watershed management approach which will help in developing the water bodies along with their surrounding areas (and vegetation) by applying several modern tools like the use of remote sensing and GIS techniques (Ren et al. 2017).
1.5.4 Urban Vegetation and CO2 Absorption
Vegetation stores a considerable amount of C in its different tissue components. Plants utilise the atmospheric CO2 in the photosynthetic pathway to produce food and store C in their tissues (e.g. stem, branch, and roots) (Velasco and Roth 2010), thus, continuously help in mitigation of CO2 emissions (Weissert et al. 2014). The C‐sequestration potential of the urban vegetation holds a key motivation for their plantation as the climate change adaptation strategies (Schadler and Danks 2011). Studies suggested that during plantation drives, those areas which have limited vegetation should be planted first followed by areas having sufficient green cover for the effective and long‐term understanding of the plant diversity, cover and health in relation to the surrounding conditions (Norton et al. 2015). Vegetation leads to reduction of atmospheric CO2 considerably as compared to the other sectors of the urban areas, particularly during the growing seasons (Vesala et al. 2008). In a comprehensive review, Weissert et al. (2014) observed that dense vegetation may act as a potential local sink of atmospheric CO2 in a city. They further reported that urban vegetation acts as a potential sink of atmospheric CO2 during the growing season in the mid‐latitude cities, whereas trees in tropical cities have the potential to absorb and sequester CO2 from the residential areas throughout the year. However, comprehensive measurements and understanding of urban vegetation C‐sequestration potential are still limited (Weissert et al. 2014). For example, the C‐sink (or CO2 uptake) potential of the urban vegetation may differ or considerably reduced when the overall emission of CO2 from the urban areas are included in the overall C‐budgeting (Weissert et al. 2014; Velasco et al. 2016; Zhao et