importance in the urban ecosystems by supporting massive biodiversity and providing ecosystems services such as temperature regulation, primary productivity, nutrient cycling, pollution reduction, carbon storage, and recreational opportunities to the human inhabitants (Dallimer et al. 2016; Lososová et al. 2018; Cubino et al. 2021). Studies revealed that climate change acts as a major driver for changes in the plant diversity, community structure, and composition (Lososová et al. 2018; Cubino et al. 2021). Plant species with different traits and origins have been supposed to respond differently to the future climate change. Based on the global climate model predictions for two representative concentration pathways (2.6 and 8.5), Lososová et al. (2018) reported that the perennial herbs and woody trees will respond more slowly to the climate change as compared to the fast‐spreading annual herbs. However, studies revealed that the responses of both native and alien plant species will be similar under changing climate conditions (Lososová et al. 2018).
Different resource conditions such as soil water availability, precipitation, nitrogen deposition, photoperiod length, and CO2 conditions also regulate the plant phenological events (Jeong et al. 2011; Cong et al. 2013). In temperate latitudes, climate change has played a major role in advancing and extending the growing seasons of plants (Menzel and Fabian 1999). Therefore, the projected climate change will alter the future species composition of the urban flora by modulating the temperature and precipitation conditions having direct impact on the plant phenological events (Neil et al. 2014; Lososová et al. 2018). Shifts in vegetation phenological events will have considerable impacts on different ecological functions which lead to the alteration in water, carbon and energy balances, and thus, primary productivity and interspecific interactions (Dallimer et al. 2016). Impact of urbanisation and climate change on the phenological events of birds (migration), amphibians (reproduction), plants (leafing and flowering), and arthropods (appearance and development) has been studied considerably (Grimm et al. 2008; Neil et al. 2010). Similarly, extensive studies have been done to measure the abundance and richness of bee species under changing climate and urbanisation conditions (Neil et al. 2014). A general decrease in bee species abundance and richness has been reported in the urban areas with respect to the climate change conditions. However, mechanistic understanding of these changes on flowering phenology and the pollinator communities is still needed to be explored (Neil et al. 2014). Therefore, for effective management of the urban green spaces, it is critically important to understand how the future plant and related pollinator communities will respond to the combined impacts of urbanisation and climate change conditions (Dallimer et al. 2016).
1.3.2.1 Invasive Species and Climate Change
As mentioned earlier, even under severe climate change conditions, the distribution and responses of both native and exotic plants will be similar. However, there will be greater chances of invasion of the alien species to the new sites which have become naturalised in the urban gardens/areas (Richardson et al. 2000; Lososová et al. 2018). Moreover, the risk of invasion will further intensify under the combination of warmer climate and urbanisation (with UHI effects), particularly in the parts of Europe (Central and Western) where native plants communities may not respond to these changes (Walther et al. 2009). In a study on the interactive effects of exotic plants and aridity, Cubino et al. (2021) observed that exotic plants showed better growth (height and leaf size) and responses under the warmer and drier regions, whereas poor responses under cooler and wetter regions as compared to the co‐occurring native plants. This further indicates the chances of the spread of invasive species in the newly warmer and drier regions mediated by the changing climate and UHI effects. Thus, there is a need to consider the interactive effects of climatic variability and invasion to know the future plant community structure and composition in different regions of the world (Cubino et al. 2021).
In the next sections, results of bibliometric analysis performed for the urban ecology‐climate change nexus have been presented, followed by the emerging features of urban ecology for the climate change mitigation.
1.4 Bibliometric Analysis for Urban Ecology and Climate Change Nexus
In order to observe the trends in research on the topics concerned with urban ecology and climate change during the past two decades (2001–2021), a bibliometric analysis was performed on 13 June 2021, using different search queries in the Scopus database (Singh et al. 2021). The search query was (TITLE‐ABS‐KEY (‘urban ecology’ AND ‘climate change’) AND PUBYEAR >1999. The query results in a total number of 137 documents published during the past two decades (from 2001 to the present, 13 June 2021). The year‐wise growth of the research on the topic of urban ecology and climate change was considered along with country‐specific research outputs. Further, institute‐wise, research area‐wise, author‐wise, and publication type‐wise distribution of research on the topic were also analysed. Though we searched from 2000 onwards, but we found that the researches are being published on this topic since 2004. Starting with merely one paper on the topic in the year 2004, the year 2020 observed a total number of 13 documents published within a single year (Figure 1.1a). Interestingly, a total of 13 papers have already been published on the topic in the year 2021 till 13 June only. This signifies the relevance of the topic and the increasing research attention in the current scenarios. The United States was the largest contributor of the papers under the country/territory‐wise publication category with 47 documents. The United Kingdom and China ranked second and third by producing 17 and 16 papers each, while India stood at eighth rank with five papers published during the same period (Table 1.1). These observations revealed that there is an ample scope for research on urban ecology‐climate change nexus in the developing countries which are expected to make a surge in urban population growth in the near future. Based on the Scopus data 2021, among the research institutes and universities globally, Arizona State University produced the maximum number of papers (8), followed by the Chinese Academy of Sciences (CAS) with six papers published during the last two decades (Table 1.1).
Figure 1.1 Bibliometric analysis results showing (a) year‐wise publication growth, (b) subject area‐wise distribution, and (c) article type‐wise publications for the search query ‘urban ecology AND climate change’.
Source: Data from Scopus database (2021).
Table 1.1 Bibliometric analysis results showing top 20 countries, top 10 research institutes/affiliations, top 20 authors, and top 10 research journal for the search query ‘urban ecology AND climate change’.
Source: Data from Scopus database (2021).
| Source category | No. of publications | Source category | No. of publications |
|---|---|---|---|
| Country‐wise | Country‐wise | ||
| United States | 47 | Belgium | 3 |
| United Kingdom | 17 | Brazil |
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