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 al. 2016). Further, the C‐sequestration potential of urban vegetation depends on climatic conditions, plant species, and management practices (Weissert et al. 2014). Temperature and precipitation are two major factors determining the plant establishment and growth attributes, thus, influencing the biomass accumulation and C‐sequestration potential (Reich et al. 2014). Thus, changing climate scenario is also considerably impacting the C‐sequestration potential of vegetation (Richards et al. 2019). Therefore, detailed spatio‐temporal variation in urban vegetation C‐storage behaviour in different regions of the world is needed to develop effective climate change mitigation strategies.
1.5.4.1 Urban Soils
The soils in the urban ecosystems have been extensively modified by different anthropogenic activities which include physical disturbances, waste deposition, filling materials, buildings, and management (irrigation and fertilisation) practices (Lorenz and Lal 2009; Raciti et al. 2012). As like urban vegetation, urban soils are the major storehouse of the C (Liu and Li 2012). Studies report that the urban soil C‐stocks (organic and inorganic) are substantial as observed in the natural ecosystems (Vasenev and Kuzyakov 2018). Interestingly, urban soils contain a massive amount of C locked inside the impervious surfaces which have limited scope for decomposition, thus, act as a potential sink of C‐stocks (Vasenev and Kuzyakov 2018). Moreover, several studies reported that the urban soils have significant potential of C‐sequestration with proper management practices (Wang et al. 2019; Upadhyay et al. 2021). With the increase in atmospheric CO2 concentration, temperature and growing seasons, and management practices, the inputs of C to the soil are also increasing which further improve the soil C‐sequestration potential (Raciti et al. 2012). However, loss of soil organic C as soil CO2 efflux with these changes in the surrounding conditions has also been observed in several studies (Raciti et al. 2012; Upadhyay et al. 2021). Therefore, there is a need to give more research attention on managing the urban soil C‐stocks and improving the ways for more C‐sequestration potential of soils, particularly in the tropical regions.
1.6 Conclusions and Future Research Directions
Humans are the major driving factors for most of the changes occurring in the urban ecosystems. Urban ecology provides a considerable understanding of the socio‐ecological dimensions of urban ecosystems in relation to the human beings. For a more effective understanding of the processes and changes occurring in the urban ecosystems, concept of urban metabolism is getting wider attention. The climate change is affecting and expected to impact more severely the urban ecosystems in the near future. Urban green spaces and related water bodies provide several ecosystem services to the humans and can be developed as potential tools for the mitigation of climate change. In addition to green spaces, green roofs and green buildings are emerging as potential approaches for sustainable urban development. With proper planning and management strategies based on the integration of various emerging tools and techniques for developing resilient and self‐regulating systems, urban ecology may help in mitigating the adverse effects of climate change on urban ecosystems.
Acknowledgements
Authors are thankful to University Grants Commission (UGC, Reference No. F.30‐461/2019 (BSR)), and Science and Engineering Research Board (SERB, Reference No. PDF/2020/001607), New Delhi, India for financial support. RS is thankful to the Director, Institute of Environment & Sustainable Development (IESD), BHU, Varanasi; and Prof. Daizy R. Batish and Chairperson, Department of Botany, Panjab University, Chandigarh for providing necessary infrastructure for writing this chapter.
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