To mitigate selection bias, a comprehensive search was conducted using the two largest article databases, Web of Science and Scopus. Furthermore, searches were performed across all fields within these databases, ensuring the inclusion of all relevant articles related to the topic in this analysis. While the choice of keywords may have introduced biases, the adherence test was employed to refine the final set of keywords and ensure accurate representation of the research areas, independent of the initial selection.

The data from both databases were merged into a single database containing 663 articles. To ensure data integrity, a visual inspection and the utilization of the R language were employed to confirm that no articles were erroneously excluded or duplicated. In order to minimize reporting bias, clear objectives were defined and utilized as a guide throughout the article selection process, which included reviewing titles, abstracts, and full texts. The stepwise approach of assessing alignment by title, then by abstract, and finally by reading the complete article was designed to establish a robust methodology suitable for large databases.

To mitigate publication and quality biases, the scientific significance of the articles was evaluated by considering their total citation count using the Pareto principle. Recently published articles, which may not have accumulated substantial citations yet, were included in the review. For articles with low citation counts and older publication dates, consultation with the authors was conducted to ascertain their quality.

These measures were implemented to minimize biases in the analysis. The flowcharts depicting the methodology, along with the availability of results at each step, demonstrate the robustness of this approach.

The analysis presented in Figure 8 of our bibliometric study reveals significant geographical inequality in publication output. The systematic review further analyzes these inequalities in the studied subtopics. Within the climate change subtopic, the cities of Singapore, Colombo in Sri Lanka, and Kampala in Uganda emerged as the most extensively studied, with India emerging as the most studied country. In the sustainable urbanization subtopic, Singapore, San Juan in Puerto Rico, and Kuala Lumpur in Malaysia stood out as the most researched cities, while India remained the most studied country. In the biodiversity subtopic, Singapore, Delhi in India, and San Juan in Puerto Rico were the cities that garnered the most attention, with Brazil emerging as the most studied country. Regarding urban resource management, Singapore, Skudai, and Kuala Lumpur in Malaysia, and São Paulo in Brazil were the most extensively studied cities, with Brazil once again being the most studied country. For a comprehensive overview of the 68 cities and regions included in our systematic review, please refer to Figure 11, which was extracted from our systematic review database.

In fact, tropical cities encompass a wide range of climates. For example, Singapore has a tropical rainforest climate (Af), Bangkok, Thailand has a tropical savannah climate (Aw), and Kerala, India has a tropical monsoon climate (Am) according to the Koppen classification (see Figure 11). Figure 8 sheds light on the current situation of countries that focus on publishing research about tropical cities, while Figure 11 illustrates the concentration of research areas within the four analyzed subtopics. Our findings indicate that India, Singapore, and Brazil were the most extensively studied regions out of the 29 countries/regions covered in our systematic review database.

Notably, a significant proportion of the studies analyzed in this review center around Singapore. This can be attributed to the city-state's international recognition as a leader in urban greening. Singapore is renowned for having over 40% green areas within its city, as reported by Stefaner et al. (2021). The city has implemented notable programs such as the Active, Beautiful, Clean Waters Program (ABC) and Green Towns Program, which promote the adoption of nature-based solutions (Tan et al., 2021). However, it is important to acknowledge that Singapore's high number of international connections, as depicted in Figure 8, could offer opportunities for other tropical cities to establish partnerships or adapt similar programs based on Singapore's experiences.

It is crucial to highlight that both the bibliometric analysis and the systematic review are based on the keyword “tropical cities” and its variations. The definition of a city as tropical is determined by the authors of each study. Figure 11 indicates a divergence in the concept of tropical cities. While the majority of authors adhere to the Koppen classification, others define tropical cities based on the tropics lines. Additionally, a minority of studies self-identify as tropical despite not fitting into these classifications, as observed in the case of Wuhan in China, Varanasi and Delhi in India, and Florianópolis in Brazil.

The bibliometric analysis was conducted with 663 articles, while systematic review was conducted with 30, 23, 30, and 85 articles in the climate change, sustainable urbanization and protecting biodiversity, urban resource management subtopics, respectively. In any case, both analyzes reveal an increasing trend in research on this topic, with a focus on the adaptation and application of methodologies used in temperate cities to the tropical context. The findings of the systematic review support the notion that publications on climate change often exhibit an international and interdisciplinary character. Notably, studies such as Velasco et al. (2016) and Manoli et al. (2019) exemplify this trend, as they employ a global study area or examine multiple tropical cities, respectively. Approximately 8% of the articles included in the review focused on a global scale, while an additional 8% examined multiple tropical cities. While publications on protecting biodiversity are more localized and specific to the area of study (e.g., Jain et al., 2018; Fragata et al., 2022). Additionally, the topic of urban resource management is the most comprehensive, with various studies covering different areas such as climate change, public health, and water resources quality (Lee M.-B. et al., 2019; Stefaner et al., 2021; Bridhikitti et al., 2022) in line with the results of the bibliometric analysis.

Moreover, the bibliometric review aligns with the findings presented in Figure 7, highlighting the interdisciplinary nature of research on tropical cities. Of the 149 articles analyzed at this stage, 46 articles were in two categories, and 6 articles were in 3 categories. That is, a third of the articles were in at least two categories similar to the value found in the bibliometric analysis showed in Figure 7. The analysis of the articles suggests that studies in tropical cities need to consider multiple aspects, such as urban heat islands, outdoor thermal comfort, carbon footprint, and protecting biodiversity. Figure 9 demonstrates that several journals publish articles on multiple subtopics, which may facilitate future research on tropical cities.

Comparing the evolution of the study of tropical cities indicated through the keywords in Figure 10 with the systematic review, it can be said that previous decade saw limited use of remote sensing techniques in studies of tropical cities. However, there is a strong trend toward the use of these techniques in recent years, as demonstrated by the systematic review. For example, Mohan and Kandya (2015) used remote sensing data to examine the impact of urbanization and land use/land cover (LULC) in Delhi, India. Similarly, Arulbalaji et al. (2020) used remote sensing data to analyze changes in vegetation cover, urban growth, land surface temperature, and LULC in Kerala, India. This evolution in the use of techniques is important, since one of the challenges in applying urban climate knowledge to planning decisions in tropical cities is the scarcity of data. While simple classification methods such as the Local Climate Zone (LCZ) have been used to classify land use and occupancy in these regions (Chatterjee et al., 2019; Kabano et al., 2021), the complexity and rapid growth of tropical cities calls for more sophisticated systems (Perera and Emmanuel, 2018). To address this data gap, Van de Walle et al. (2021) proposed a low-cost fieldwork approach using a cost-effective methodology to gather relevant parameters that effectively capture urban heterogeneity in terms of morphology and building materials. This approach is particularly useful for urban climate studies utilizing Local Climate Zones (LCZ) in small and medium-sized cities. The increasing utilization of remote sensing techniques in tropical cities may be attributed to these studies and others like them.

Further, the main focus of climatological research on tropical cities from 1996 to 2006 was on issues related to air quality (Roth, 2007). However, current research on tropical cities has become more diverse, and keywords such as “black carbon” and “aerosol and particles” have now a median in 2013 and 2015 respectively as indicated in Figure 10. The review of articles in our database on the subtopic of climate change showed that only one dealt specifically with this topic. Badarinath et al. (2010) found that aerosols contribute to a continuous solar dimming effect over Hyderabad, India. However, other articles in the category of urban resource management addressed this issue. Indicating the tendency of the study of tropical cities to become broader and involve more than one area of knowledge.

Again, in the protecting biodiversity subtopic, the word pollinators in Figure 10 is also in line with the systematic review where it was found that pollinators in tropical cities revealed important information about the impacts of urbanization on biodiversity. Also, in the urban resource management subtopics, some research support the design of urban environments that are sensitive to climate is crucial for human health and comfort. This is in line with the bibliometric analysis that demonstrated a growing trend of keywords related to this topic, such as “public health” and “urban planning” in recent studies (see Figure 10). These trends will be discussed in more detail in subsequent sections of the paper.

In addition, research has shown that tropical regions are lagging behind in terms of urban resource management when compared to temperate regions, as noted by Jochner et al. (2013). This can be attributed to the greater presence of developing countries and lack of political and economic incentives in tropical cities. However, in the past decade, there has been a notable increase in research on this topic, as evidenced by the upward trend in publications (see Figure 5).

Forecasting future climates in urban areas is crucial for the implementation of effective mitigation and adaptation strategies. However, limited research has been conducted on future temperature projections in tropical cities. To address this gap, He et al. (2022) utilized a statistical method to downscale global climate modeling results to the city scale and employed an urban morphological approach to estimate the impact of urbanization on air temperature in Singapore. Conducting such studies in tropical cities can significantly enhance our understanding of the dynamics of global climate change. Furthermore, investigating climate change in tropical cities is of paramount importance because the effects of climate change can extend beyond the boundaries of a specific location and impact the region and the world as a whole, so the unplanned rapid expansion of tropical cities is not a local problem (Roth, 2007).

Moreover, despite its crucial relevance for water resource management, flood risk reduction, drought mitigation, and the design of ecologically sustainable cities, research on precipitation spell characteristics in tropical urban areas remains limited (Lo and Koralegedara, 2015; Li et al., 2016). Given the complex precipitation patterns exhibited by tropical cities, access to spatial and temporal precipitation data is indispensable for effective water resource management. However, financial constraints often hinder the availability of high-resolution data in many regions. Combining spatial downscaling and temporal disaggregation techniques can offer valuable projections of high-resolution rainfall data. Unfortunately, only a few studies of this nature have been conducted in tropical cities, with one example being the study conducted by Lu and Qin (2014) in Singapore.

Examining the influence of urbanization-driven land-use changes on local hydrometeorological processes, Pathirana et al. (2014) observed an increase in local extreme rainfall with the growth of urban areas in Mumbai, India. However, the relationship between urbanization and rainfall is non-linear and depends on various localized factors such as topography, surrounding land use, and local/seasonal climate patterns. For instance, Li et al. (2017) investigated long-term trends in extreme precipitation in Singapore and found that the impact of local factors on precipitation extremes outweighs the effect of global warming. Consequently, further studies on this topic are necessary to gain a comprehensive understanding of the complex interplay between urbanization and rainfall patterns.

Anthropogenic activities have a significant impact on the urban microclimate, particularly through the urban heat island (UHI) phenomenon, where urban areas exhibit higher temperatures compared to surrounding regions, exacerbating heat waves. Marcotullio et al. (2021) conducted a study on 270 tropical cities globally and found that all cities in the tropics have experienced warmer conditions. Notably, cities in rainforest and monsoonal zones have witnessed an intensified UHI effect, resulting in increased urban warming. In addition, Chew et al. (2021) conducted research in Singapore during a heatwave and found no amplification of UHI intensity, which differs from studies conducted in temperate cities showing a positive correlation between heatwaves and UHI. Although studies focusing on heat waves in tropical cities are relatively scarce, they are essential for enhancing our understanding of UHI dynamics and heat wave impacts.

Mitigating the effects of UHIs in tropical cities, is widely acknowledged as necessary. However, Roth and Chow (2012) highlighted the limited availability of information regarding the environmental benefits of proposed greening options and the lack of data on current climate interventions employed in Singapore. Despite these limitations, some progress has been made in understanding the impacts of various strategies to mitigate UHI in tropical cities. For instance, Benrazavi et al. (2016) analyzed the effect of pavement materials on surface temperatures in Putrajaya, Malaysia. Herath et al. (2018) demonstrated that trees on curbsides, green roofs, and green walls can influence microclimatic conditions and potentially mitigate UHI in Colombo, Sri Lanka. Chatterjee et al. (2019) conducted simulations to assess the effectiveness of different mitigation strategies, such as cool pavements, cool roofs, and increased urban vegetation, in reducing UHI intensity in Kolkata, India. Koranteng et al. (2021) suggested that green roofs may be a viable solution to alleviate indoor thermal discomfort in Kumasi, Ghana. Gamero-Salinas et al. (2021) found that passive cooling design strategies, including natural ventilation, wall absorptance, and wall thermal transmittance, can significantly reduce the risk of overheating in Tegucigalpa and San Pedro Sula, Honduras. Additionally, Dayathilake et al. (2021) demonstrated the high carbon storage potential of urban freshwater wetlands in Colombo, Sri Lanka. However, further research is necessary to enhance our understanding of the effectiveness of different mitigation strategies in tropical cities and their associated environmental benefits.

In the context of climate change, it is crucial for tropical cities to adapt their policies to mitigate its impacts. While traditional solutions such as transitioning away from outdated technologies and promoting public transportation have been extensively discussed in the literature, innovative approaches like nature-based solutions have received limited attention in tropical cities, particularly within South America (Reynolds et al., 2017). Several studies have indicated the potential environmental benefits of street trees in reducing air temperature, humidity, and air pollution, as demonstrated by Vailshery et al. (2013) in Bangalore, India. Similarly, research by Morris et al. (2017) in Klang Valley, Malaysia, highlighted the role of urban vegetation in mitigating the formation of UHI. However, Velasco et al. (2016) found that the impact of urban vegetation on directly reducing greenhouse gas (GHG) emissions through carbon sequestration is limited or negligible, even in tropical cities.

Moreover, there exists a gap in our understanding of the phenology of individual trees or specific tree species in tropical cities (Jochner et al., 2013; Kabano et al., 2020, 2021), which is crucial for urban tree management as phenological observations in urban areas can help assess microclimatic conditions. Furthermore, the complex interactions between the built environment and vegetation make it challenging to evaluate the contribution of vegetation to a city's radiative budget. Recent studies by Dissegna et al. (2019) have suggested the potential of physically-based radiation transfer models, such as the Discrete Anisotropic Radiative Transfer model, for neighborhood-scale analysis and scenario testing with different surface materials and vegetation properties, providing a better understanding of UHI dynamics in tropical contexts.

Furthermore, gaining a deeper understanding of the ecosystem services and economic values associated with urban forests is essential for the implementation of effective urban forest management policies (Jim and Chen, 2009). Implementing nature-based solutions requires multidisciplinary studies that encompass various aspects relevant to tropical cities.

Additionally, the effectiveness of different cooling solutions is influenced by the nonlinear interactions between the local climate, vegetation characteristics, and the built environment. Research by Manoli et al. (2019) revealed that increasing green cover and albedo are more effective in dry regions, while tropical cities require more innovative solutions. Consequently, UHI mitigation strategies commonly employed in temperate cities need to be adapted to the tropical context, considering that the energy balance mechanisms in the tropics differ from those in mid-latitudes (Chatterjee et al., 2019).

Moreover, the impacts of climate change on tropical cities can have significant social and economic consequences. Méndez-Lázaro et al. (2016) highlighted the increased effect of high temperatures on mortality, particularly from stroke and cardiovascular disease, in Puerto Rico. Ramsay et al. (2021) demonstrated that heat stress approached the upper limits of human thermoregulatory capacity in informal settlements in Makassar, Indonesia. Furthermore, Upadhyay et al. (2021) indicated that variations in soil temperature and moisture conditions under climate change scenarios may hinder future soil carbon dynamics by mediating soil nutrient availability in urban soils in Varanasi city, India. Understanding the effects of climate change on urban tropical areas is also crucial for addressing issues like eutrophication and pollution (Silva et al., 2019) and for flood damage estimation and mitigation (Tabucanon et al., 2021). Therefore, when planning for sustainable, biodiverse, and resource-efficient tropical cities, it is essential to consider these social and economic impacts.

Finally, climate change is compelling city governments to adopt innovative and creative approaches to urban planning as traditional practices have reached their limits (Yulia and Arlianda, 2020). Biswas et al. (2022) found that the holistic implementation of climate change adaptation for water resources is rare and still in its early stages due to a lack of quantifiable implementation frameworks or audit processes. This is likely to be the case for many tropical cities in different regions, which often face challenges such as poor data availability and limited access to financial resources. Currently, there is a gap in standards that can assist tropical cities in adapting to climate change. However, considering the dynamic and uncertain nature of climate change, it is more beneficial to develop plans that can be adapted as the future unfolds, such as the development of dynamically robust plans (Manocha and Babovic, 2018).

Many studies in this subtopic focus on characterizing the urban heat island (UHI), effects similar to the previous subtopic, but here they aim to build cities suitable for the well-being of human beings and the environment. For instance, Souto and Cohen (2021) utilized satellite images from 2003 to 2018 to examine the relationship between increased land surface temperature and dense urbanized areas, as well as their surroundings in the metropolitan region of Belém, Brazil. In a study conducted in Singapore, Jin et al. (2018) found that the building plot ratio (the ratio of total floor area to total land area) and sky view factor were the most significant parameters influencing daytime air temperature. Similarly, Kotharkar et al. (2019) identified the distance from the central business district, surface albedo, aspect ratio, and vegetation density ratio as major factors contributing to UHI occurrence in Nagpur, India.

In addition to investigating UHI phenomena, sustainable urbanization research often explores outdoor thermal comfort (OTC). Rajan and Amirtham (2021) emphasize the close link between UHI and OTC, highlighting how proper urban planning can mitigate the UHI effect and enhance OTC through the creation of vegetated parks and the preservation of forested areas, especially those with large, dense canopies. Haddad et al. (2020) proposed a holistic approach to mitigate UHI effects and improve OTC in tropical cities, demonstrating that a combination of cool materials, shading, and greenery in urban areas effectively reduces temperatures and enhances thermal comfort in Darwin, Australia. However, there is limited research specifically focused on users' perception of OTC. Das et al. (2020) conducted a study in Eastern India that associated field measurements of thermal indices with questionnaire surveys to evaluate the subjective thermal sensation of outdoor spaces. Their findings revealed a strong correlation between objective and subjective parameters related to OTC.

While adopting mitigation strategies is crucial for achieving sustainability in urban areas, it is important to plan these strategies carefully to avoid resource misuse and ensure their success. For example, Lin and Tsai (2017) conducted a study in Taiwan, demonstrating that planting appropriate tree species can improve OTC in tropical climates. Acero et al. (2019) investigated the impact of vertical green systems (VGS) on pedestrian thermal comfort in Singapore and found that benefits are not expected to be noticed at a distance >3 m from the facade with its geographical orientation also influencing its thermal performance. Furthermore, Zaki et al. (2020) demonstrated the influence of roadside tree orientation on outdoor air temperature in Kuala Lumpur, Malaysia. Vailshery et al. (2013) highlighted the positive effects of tree plantation along roads, including reduced air and road temperatures, as well as lower air pollution in Bangalore, India. These findings underscore the need for multidisciplinary strategies that consider various factors to effectively address the challenges of UHI and OTC in tropical cities.

Moreover, the consideration of carbon footprint and offset is crucial in the pursuit of sustainable urban environments. Reynolds et al. (2017) compared different carbon offset techniques and found that public trees are a competitive option in a Colombian metropolitan area, outperforming alternatives such as cable car public transportation. Nadeeshani et al. (2021) evaluated the life cycle carbon footprint of conventional building roofs vs. green roofs in Colombo, Sri Lanka, and discovered an 85% reduction in carbon footprint with the implementation of green roofs.

In addition to green roofs, other sustainable drainage systems have been studied as well. Chui and Trinh (2016) found that converting 5% of a Singapore catchment area into bioretention systems would enhance infiltration and groundwater recharge. Other strategies such as protecting remaining forests, planting multi-layered vegetation, and restoring urban soils have also been proposed to help with flood regulation and carbon sequestration (Fung et al., 2021).

Several studies have evaluated the adoption of green strategies at the yard and indoor levels, providing valuable insights for urban planners in terms of urban zoning and the implementation of incentive policies. Meléndez-Ackerman et al. (2014) found strong associations between yard characteristics and household demographic profiles in Puerto Rico, with yard size emerging as the most important factor influencing vegetation diversity and quality. Oh et al. (2018) conducted a study in Singapore and discovered that corridor and building design significantly influenced the abundance and diversity of vertical greenery, emphasizing the importance of incorporating plant requirements into urban space design to enhance the synergy between humans and flora.

Thus, the synergy between urbanization and ecosystem services provision is a key aspect of sustainable urbanization. Tan et al. (2021) conducted a case study in Singapore and demonstrated that the consistent application of nature-based solutions across all elements of urban development significantly enhances urban ecosystem services. In fact, Singapore serves as a long-term case study for tropical urban ecosystem services, with evidence of these services being present in the city-state since the nineteenth century. Further, case study of Singapore serves as a model to other cities across the tropics, considering its experience with the urban-green continuous conflicts (Friess, 2016).

To summarize, the reviewed literature on this subtopic provides valuable technical information on urbanization in tropical regions. Local study areas were utilized to explore the challenges associated with urban growth and evaluate strategies for minimizing these issues. However, there is a limited exploration of the effects of urbanization and mitigation strategies beyond the microscale. Additionally, there is a lack of studies evaluating the relationship between knowledge generation and its practical application. Achieving sustainable strategies in tropical urban environments requires not only scientific advances but also effective management of the politics and visions arising from complex governance systems. In this sense, the use of knowledge-action systems could be useful to enhance the ability of decision-makers, scientists, and planners to work together in the aim to achieve sustainable strategies within the tropical urban environment (Muñoz-Erickson, 2014).

The articles selected for this subtopic demonstrate investigations into various species and aspects, which aligns with the diversity of fauna and flora in tropical regions. However, birds and avian species are the most studied animal group, as their observation in urban areas is relatively simple and accessible. In terms of human presence and disturbance, Wolff et al. (2018) and Lee M.-B. et al. (2019) evaluated how local-scale features of an urban tropical city can affect the richness and occupancy of avian species, specifically in the San Juan Metropolitan Area, Puerto Rico and Nanning, China, respectively. They found that noise, population density, building height and proportion of commercial buildings have negative impacts on bird presence. Additionally, Estela et al. (2021) examined how the nocturnal activity of birds in the tropical city of Cali, Colombia changed during the COVID-19 pandemic lockdown and found that there was an increase in bird activity during the strict circulation period, highlighting the impacts of changes in human activity on urban biodiversity.

Furthermore, Dri et al. (2021) developed a model that combines historical aerial imagery and current species distribution data to examine the effects of urbanization on habitat loss and isolation in birds in Florianópolis, Brazil. Their findings indicate that habitat loss is the primary cause of species extinction in urban areas, and that cities can rapidly promote biodiversity by preserving or restoring forest cover. Fragata et al. (2022) studied the patterns of diversity and abundance of parrots in the tropical city of Manaus, Brazil and revealed that the quantity of green areas in the city is a major driver of parrot diversity and composition, linked to the urbanization process of the city. Sultana et al. (2022) investigated the effects of urban land cover and socioeconomic factors on resident bird species richness and abundance in the tropical megacity of Dhaka, Bangladesh. They found that increasing impervious areas result in low bird richness, while bird abundance is increased in areas with high habitat heterogeneity and near green areas, and that regions with rising poverty decrease birds' abundance. Tang et al. (2015) studied the population genetics of a bird species affected by urbanization in Singapore and discovered high genetic diversity and evidence of population growth, suggesting that conservation of bird species may be possible despite the fragmentation of green areas.

Besides, some studies have investigated strategies to ensure bird biodiversity in tropical cities. Thaweepworadej and Evans (2022) found that urban woodlands can moderate the negative impacts of urbanization on avian species richness in Bangkok, Thailand, suggesting strategies to design such woodlands to maximize biodiversity protection and conservation benefits. Rawal et al. (2021a) evaluated winter bird's abundance, species richness and functional guild composition in ponds of a major tropical city Delhi, India. In the same study area, Rawal et al. (2021b) investigated the bird diversity in the ponds and its relationship with site-level (pond size, water quality, shoreline heterogeneity, wetland vegetation, and others) and landscape variables (impervious surface, proximity of local ponds, extent of wetlands and others). Their findings highlight the importance of preserving ponds, as they are a refuge to hundreds of birds in tropical megacities. However, further research is needed to fully understand the impacts of these strategies, particularly in regard to the effects on bird molting and the role of urban resource planning in biodiversity conservation. Therefore, the literature on the impact of urbanization on bird biodiversity in tropical cities underscores the complexity of the issue and the need for interdisciplinary research.

The studies of butterflies and pollinators in tropical cities have revealed important insights into the impacts of urbanization on biodiversity. Jain et al. (2018) examined the temporal trends of butterfly extirpations and discoveries in Singapore, highlighting the rapid urbanization of this tropical city. Gupta et al. (2019) evaluated the changes in butterfly diversity in urban tropical areas, specifically examining the effects of temperature and humidity changes in Delhi, India. Their findings indicated that temperature gradients can greatly influence urban landscapes and their biodiversity. Oliveira et al. (2018) studied how an urban reserve affects the diversity of butterflies in public squares in Natal, Brazil. They observed a notable difference between the butterfly communities in the reserve and those in the public squares, suggesting limited dispersal from the reserve to the surrounding areas, despite the presence of green cover and resources. Similarly, May-Itzá et al. (2021) identified differences in bee communities between urban and rural areas, likely attributed to resource limitations and mating conditions in Merida, Mexico.

Furthermore, Nascimento et al. (2020) conducted a systematic review of 86 studies on urban plant-pollinator interactions in Brazil, aiming to understand the role of urban green spaces in preserving pollinator diversity in tropical cities. The authors found that despite the negative impacts of urbanization, tropical urban areas can support a diverse array of pollinator species. Cézar et al. (2022) also highlighted the importance of considering changes in pollinator communities and their impact on fruit production, emphasizing that the relationship between pollinators and plants must be considered in conservation efforts. These findings demonstrate the need for an effective pollinator conservation plan that considers these multiple factors.

In addition to the species mentioned above, several other studies have explored different facets of biodiversity in tropical urban environments. Ganci et al. (2021) investigated frog species richness and composition, Lippert et al. (2020) studied communities of protozoans in a tropical urban stream, Andrade (2019) focused on lagartixas, a common lizard found in Brazil, de Jesús-Crespo and Ramírez (2011) examined macroinvertebrate assemblages, Izuddin et al. (2019) explored orchid mycorrhizal fungi found in trees within urban environments, and Alves-de-Souza et al. (2017) analyzed eukaryotic phytoplankton in coastal lagoons. These studies collectively emphasize the importance of considering biodiversity as an indicator of the impact of human expansion on the environment and highlight the need to incorporate biodiversity considerations into conservation and management strategies.

In the context of conservation of plants and trees in tropical cities, some studies have highlighted that despite the importance of urban green spaces, the presence of exotic species is common due to lack of proper management. For example, Silva et al. (2020) evaluated the species of trees planted in green spaces of tropical urban areas in northeastern Brazil. They found a high proportion of exotic plants, which could negatively impact native species in terms of pollination and colonization. Similarly, Oliveira et al. (2020) investigated the role of urban green spaces as repositories of natural forests and found that the dominance of exotic plants limited their ability to serve as biodiversity repositories in Recife, Brazil. These findings underscore the need for proper management to mitigate the negative impacts of exotic species and enhance the conservation value of urban green spaces.

Additionally, research have also examined the relationship between species and the urban environment, highlighting how the implementation of green spaces in different locations can contribute to biodiversity protection and conservation. For instance, Jim (2013) evaluated the abiotic and biotic conditions for tree growth on stone walls in Hong Kong, while Wang et al. (2017) observed bird and butterfly visitors at a tropical roof garden in Singapore, both indicating the importance of proper dimensions and design for these spaces to attract wildlife.

Besides, Oh et al. (2018) presented an in-depth analysis of the presence and distribution of greenery along high-rise residential corridors in Singapore, highlighting the potential of these green urban areas as refuges for native species, providers of ecosystem services, and facilitators of human-nature interactions. Belcher and Chisholm (2018) quantified the economic value placed on vegetation areas by homebuyers in proximity to residential areas in Singapore. They determined that homebuyers placed higher value on managed vegetation, such as parks and street trees, compared to spontaneous or natural areas. Overall, these studies emphasize the importance of careful planning and management of urban green spaces in tropical cities to ensure their effectiveness in promoting sustainability and conserving biodiversity.

The analyzed studies in this subtopic reveal a lack of urban resource planning, consistent with the trends highlighted in previous topics. Changes in LULC, particularly the expansion of impermeable areas with reduced ecosystem functions (Tan et al., 2021), have led to air quality degradation (Ooi et al., 2019; Nipen et al., 2022), temperature changes (Aktas et al., 2020; Meili et al., 2021), and increased sensible heat absorption, exacerbating UHIs (Li et al., 2013; Carrillo-Niquete et al., 2022). In fact, UHIs can be influenced by multiple factors, including climate, society, and the economy (Li et al., 2020), and can have various impacts on both people and the environment, as previously discussed (Kotharkar et al., 2020; Acero et al., 2021; Kabano et al., 2021). Therefore, understanding this phenomenon within the context of each tropical city is crucial to assist in urban resource management (Amorim, 2018; Isa et al., 2020).

Enhancing the ability of tropical cities to adapt to UHIs and climate effects requires multidisciplinary planning of urban resources. One approach is to mitigate damage through technical guidance for building features in high-density urban areas (Chen et al., 2010; Rodríguez-Algeciras et al., 2018; Bartorila and Rosas Lusett, 2021) and increasing green areas to enhance their benefits, such as microclimate control (Ali and Patnaik, 2019). For instance, highly urbanized landscapes without tree cover can absorb up to four times more heat compared to densely vegetated natural landscapes (Dissegna et al., 2019). Thus, implementing green building and environmental initiatives, such as replacing existing roof structures with green roofs, is another viable strategy (Ali and Li, 2018). Other strategy can involve utilizing available radiation as an opportunity for solar energy generation in different urban topologies, as demonstrated in studies conducted in Brazil (Martins et al., 2014) and Tanzania (Lau et al., 2017).

Appropriate management of urban resources, including sustainable planning of LULC and conscious expansion of green areas and water bodies, can enhance ecosystem functions (Fung et al., 2021; Olivero-Lora et al., 2022). This, in turn, leads to higher biodiversity (Abendroth et al., 2012; Chang and Lee, 2015; Barbosa et al., 2020; Hwang et al., 2021), improved pollination processes (Albuquerque-Lima et al., 2022), and effective control of illness-vector mosquitoes (Skovmand et al., 2011; Lee J. M. et al., 2019).

Green areas also play a role in storm water interception (Nytch et al., 2018), and when implemented on green roofs, they can remove pollutants and heavy metals (Lim et al., 2021) while mitigating diffuse pollution effects through bioretention basins (Chui and Trinh, 2016). However, it is important to note that the choice of soil and substrate used can impact nutrient levels in water and become a water quality issue if not managed properly (Lim et al., 2021).

Moreover, these green spaces can have economic implications for tropical cities. For instance, Belcher and Chisholm (2018) demonstrated that vegetation has positive effects on property selling prices in Singapore. However, it is important to acknowledge that not all tropical cities have the same resources for implementing green infrastructure. Oliveira and Ahmed (2021) highlighted the challenges faced in Ghana and other African countries, such as a lack of trained professionals, financial incentives, and effective public policy management, which hinder the realization of environmental and socioeconomic benefits from green and blue infrastructure.

Besides, considering the historical context of tropical cities, understanding past actions and their consequences is important for supporting future decision-makers (Scarborough and Isendahl, 2020; Evans et al., 2021). Historical research has highlighted the benefits of sustainable adaptations and connectivity in tropical urban cities (Scarborough and Isendahl, 2020), as well as the soil security achieved by ancient societies such as the Maya (Evans et al., 2021). These studies demonstrate that preserving green areas increases environmental awareness and a sense of belonging to space. Similar investigations can be conducted to characterize social and environmental dynamics in other historical civilizations in the tropics.

Extreme hydrological events, such as inundation, pose significant risks that can be better understood through hydrodynamic simulations. These simulations aid in risk mitigation by controlling peak discharges, facilitating communication with society and water managers (Tabucanon et al., 2021; Chitwatkulsiri et al., 2022; Mattos et al., 2022), and assisting in the design of water management systems (Manocha and Babovic, 2018).

In fact, water resources play a crucial role in the development of urban resource policies (Biswas et al., 2022). Understanding water quality impacts, including their origin, is addressed through various monitoring studies (Chow et al., 2013a,b; Chow and Yusop, 2014). Some studies have explored the relationship between eutrophic tropical reservoirs and greenhouse gas emissions (de Mello et al., 2017; Pierangeli et al., 2021), while others emphasize the importance of studying eutrophic reservoirs for public health assurance (You et al., 2015; López-Doval et al., 2017; Silva et al., 2019; Malta et al., 2022).

Spatial and temporal assessment of surface water quality provides valuable information for formulating evidence-based water resource management strategies by local governments (Othman et al., 2012; Mena-Rivera et al., 2017; Bridhikitti et al., 2022; Marinho et al., 2022). Additionally, studies focused on water treatment have explored the use of different algae species for pollutant removal via phytoremediation (Anne et al., 2021), while the separation of yellow water, brown water, and gray water shows promise in improving the management of domestic wastewater in a sustainable manner (Zhang et al., 2013; Ng et al., 2014). In addition, in situ monitoring research and computational hydrodynamic simulations are essential for sustainable development in tropical cities, as the quantitative and qualitative aspects significantly impact the environment (Chow et al., 2012; Hasan et al., 2019).

Furthermore, studies conducted on this subtopic have investigated atmospheric composition and air quality by examining photochemical processes (Soni et al., 2022), wet deposition of secondary atmospheric pollutants like nitrate (Villalobos-Forbes et al., 2021), ozone and particulate matter (PM) measurements (Barima et al., 2014; Salvador et al., 2022), the impact of biomass burning on PM composition (Yang et al., 2013), and the effects of peat-forest burning on PM (Lan et al., 2021).

In summary, effective urban resource planning in tropical cities requires a comprehensive and multidisciplinary approach. This approach should consider socio-economic factors, for example, the morphological and chemical characteristics of the soil, the impacts of extreme weather events, and the potential use of solid waste for energy generation and cooling (Udomsri et al., 2011; Upadhyay et al., 2021; Olivero-Lora et al., 2022). Additionally, it is crucial to ensure that urban resource planning concepts are equitable and accessible to all, regardless of education or economic power (Muñoz-Erickson et al., 2014; Martinuzzi et al., 2021; Takakura and Massi, 2021).

The research conducted on tropical cities in relation to climate change underscores the importance of understanding the impacts of this phenomenon on urban areas. The social and economic consequences of climate change in tropical cities extend beyond local boundaries, making it a global concern. Additionally, the unique climatic dynamics in tropical cities can provide valuable insights into several themes, such as the association between extreme events and urbanization. Furthermore, investigating the influence of urbanization-driven land-use changes on local hydrometeorological processes and forecasting future climates in tropical urban areas can significantly enhance our comprehension of the dynamics of global climate change.

Further, limited research has been conducted on future temperature projections and precipitation spell characteristics in tropical cities, highlighting the need for further studies in these areas. Studies have shown a correlation between increase in urban tropical areas and extreme urban rainfall, however, this relationship is complex and influenced by factors such as local topography, surrounding land use, and specific climate patterns. Since the management of water resources and extreme events are essential for sustainable development in tropical cities, more research is needed in this area to fully understand the dynamics of precipitation in tropical urban areas.

Many studies on sustainable urbanization, climate change, and urban resource management in tropical cities have focused on characterizing the effects of the UHI phenomenon. These studies suggest that addressing UHI needs a multidisciplinary effort that must consider both climate and urban planning factors. However, there are gaps in understanding this phenomenon, such as the dynamics of UHI and heatwaves in urban tropical regions. Understanding the complex interactions between the built environment, vegetation, and climate is crucial for effective UHI mitigation and adaptation strategies.

Various strategies have been employed in tropical cities to mitigate the effects of climate change on the UHI phenomenon, such as cool pavements, cool roofs, green walls, and passive cooling design strategies. However, challenges remain in implementing these strategies effectively. Firstly, limited availability of information regarding the environmental benefits of proposed greening options and insufficient data on current climate interventions hinder progress. Secondly, the nonlinear interactions between local climate, vegetation characteristics, and the built environment further complicate the effectiveness of these strategies. Hence, innovative solutions specifically tailored to the tropical context are necessary, i.e. global and multi-scale understanding, linking physical-chemical processes, transport and thermodynamics approaches with optimization, like deep learning and numerical simulation.

The implementation of cooling solutions in tropical cities requires careful consideration of local climate and vegetation characteristics. Simply applying solutions from temperate cities may not yield the desired results. Due to the complexity and diversity of tropical cities, strategies must be tailored to each specific location. To ensure the success of these solutions, research must be conducted across a range of different tropical cities. However, unfortunately, there is a lack of guidelines or standards to assist these cities that are particularly vulnerable to the effects of climate change. Another challenge lies in the absence of quantifiable implementation frameworks or audit processes. The lack of standards that can guide tropical cities in adapting to climate change exacerbates this issue.

Nature-based solutions, such as urban trees and green infrastructure, hold promise for mitigating climate impacts in tropical cities. Their implementation in tropical cities aligns with the United Nations' Sustainable Development Goal 11 to create inclusive, safe, resilient, and sustainable cities (United Nations General Assembly, 2015). However, a knowledge gap remains concerning the phenology of individual trees or specific tree species in tropical cities, which is crucial for effective urban tree management. For example, policies for the implementation and conservation of urban trees should consider environmental factors, the species' ability to adapt to the local environment, their ability to combat climate change, and their impact on local biodiversity. It's important to note that the conservation efforts should be well-performed and substantiated to avoid the introduction of exotic species into tropical cities and potential ecological impacts. Furthermore, understanding the ecosystem services and economic values associated with urban forests is essential for the implementation of effective urban forest management policies. Comprehensive multidisciplinary studies addressing these aspects are crucial for effective implementation of Nature-based solutions.

Moreover, the studies on the sustainable urbanization subtopic explore the relationship between urbanization and UHI, the influence of factors like vegetation, building design, and geographical orientation on outdoor temperature and thermal comfort, and the potential of green infrastructure such as green roofs and bioretention systems to mitigate climate impacts. Furthermore, the studies discuss the importance of considering carbon offset and reduction strategies, such as public trees and green roofs, and highlights the benefits of sustainable drainage systems and the preservation of forests for flood regulation and carbon sequestration. It also touches upon the significance of incorporating nature-based solutions into urban development.

In addition, studies have revealed the effectiveness of mitigation strategies such as utilizing vertical green systems and considering road orientation in addressing climate change and urban resource management in tropical cities. However, it is important to note that these strategies must be carefully planned and implemented to avoid the misuse of resources and ensure their success. In addition, these strategies need to consider social and economic aspects to ensure that such measures are beneficial to the entire population. Some findings suggest that incorporating plant requirements into the design of urban spaces can improve the synergy between human and flora.

Regarding the subtopic protecting biodiversity, these studies explore the impact of urbanization on biodiversity in tropical cities, focusing on various animal groups and aspects. Studies demonstrate how the expansion of cities and associated human activities affect various species and ecosystems within urban environments. In general, urbanization can lead to habitat loss, fragmentation, and degradation, resulting in declines in species richness and abundance. Other negative impacts include noise pollution, changes in land use patterns, loss of green spaces, and alteration of natural habitats.

Moreover, studies suggest that conservation efforts can be successful despite the fragmentation of green areas. Strategies such as urban woodlands and preserving ponds are found to protect bird biodiversity in tropical cities. Urban green spaces in tropical cities can support diverse pollinator species, and conservation efforts need to consider the relationship between pollinators and plants. The presence of exotic species in urban green spaces highlights the need for proper management to protect native species. The location and design of green spaces influence their attractiveness to wildlife.

These findings emphasize the importance of understanding these impacts to develop effective strategies for biodiversity conservation and sustainable urban development in tropical cities, where unique contexts for studying the interactions between urban environments and biodiversity are found, due to the specific challenges and opportunities presented by tropical climates, landscapes, and urbanization patterns. Given the increasing rate of urbanization in tropical cities, it is essential to conduct further research to ensure the preservation of biodiversity.

The research on tropical cities in relation to urban resource management highlight the lack of urban resource planning, which has led to various negative impacts such as air quality degradation, temperature changes, and UHI effects. To address these issues, multidisciplinary planning is necessary, such as including technical guidance for building features and increasing green areas. Proper management of urban resources can enhance ecosystem functions, biodiversity, and control illness-vector mosquitoes. Green areas also play a role in storm water interception and pollutant removal. Economic implications of green infrastructure are noted, but challenges in implementing such initiatives in some tropical cities are acknowledged. Water resource management strategies should be evidence-based and consider spatial and temporal assessments. Studies on atmospheric composition and air quality are also important. In summary, effective urban resource planning requires a multidisciplinary approach that considers socio-economic factors and ensures equitable access for all.

However, these studies analyzed in our study also acknowledge some limitations, including the lack of research beyond the microscale and the need for more comprehensive studies on the practical application of knowledge generation. It emphasizes the importance of effective governance systems and collaboration between decision-makers, scientists, and planners to achieve sustainable strategies in tropical urban environments. These studies provide valuable insights into the challenges of climate change in tropical cities and offer various strategies and case studies for sustainable urbanization, protecting biodiversity and management urban resources. It underscores the need for multidisciplinary approaches and emphasizes the role of governance and collaboration in implementing effective solutions.

Despite its strengths, the bibliometric review methodology employed in this study does have certain limitations that should be acknowledged. Firstly, our analysis focused exclusively on articles published in English within the international review literature in the Web of Science and Scopus databases, using a specific set of keywords. This approach inherently excludes articles in other languages, as well as those in different document formats such as books and technical reports. Additionally, articles pertaining to tropical cities that do not contain any of the keywords examined in this study were not considered. This selection bias may have restricted the inclusivity of our analysis.

Another limitation arises from the qualitative analysis involved in the systematic review. The subjective aspects in determining the alignment of the analyzed documents with the study objectives, as well as the presentation of results, introduce a level of subjectivity. Furthermore, given the evolving nature of the topic of tropical cities, the temporal scope of this analysis may become outdated as new research emerges.

It is also important to note that only a limited number of the selected articles addressed the institutional and cultural challenges associated with the implementation of new techniques or practices in tropical cities. Although the work by Emmanuel (2018) highlighted some institutional and cultural challenges in implementing passive climate-sensitive design strategies in tropical regions, further research is needed to comprehensively address these aspects.

Other aspects relevant to the topic of tropical cities, including energy management, technologies for renewable energy sources, and agricultural prospects, were not discussed in this study. This omission is primarily due to the absence of these topics in our database or their limited prominence in the analyzed studies.

Additionally, while certain mitigation practices such as nature-based solutions were discussed across the four analyzed subtopics, the interdisciplinary and innovative exploration of these solutions requires additional studies using alternative frameworks.

Furthermore, our research provides a broad overview of trends across tropical cities in subtopics of climate change, sustainable urbanization, protecting biodiversity, and urban resource management. However, to determine the practical applicability of these trends in specific city contexts, more specific studies are necessary.

Notwithstanding these limitations, it is important to highlight that the proposed methodology recognizes and accounts for these limitations, taking proactive steps to mitigate potential biases as discussed in the assessment of risk of bias topic.