Background

Rising global temperatures, a characteristic of recent decades, are leading to an exponential increase in vapor pressure deficit (VPD) and soil droughts worldwide [3]. This warming trend is considered one of the most significant threats to human health in the 21st century [14]. Climate change can also have profound consequences for animal movements and interactions between animals and humans [6].

In India, urbanization combined with regional climate change-induced warming contributes to a phenomenon known as the Urban Heat Island (UHI) effect [2]. This effect causes urban areas to experience temperatures that are 1–4 °C higher than their surrounding rural counterparts [2]. Such temperature differences pose considerable risks to biodiversity, human health, and regional climate systems [2].

Human activities, including population growth and industrialization, intensify the demand for food and supplies, leading to the occupation of forest areas and increased contact with wildlife [7]. These actions, alongside climate change, can disrupt ecosystems and affect the planet's climatic and ecological balance [7].

Key findings

  • Urbanization and climate change contribute to the Urban Heat Island (UHI) effect in Indian cities, where urban areas are 1–4 °C warmer than rural areas [2]. This phenomenon was investigated across 141 Indian cities over two decades, from 2001 to 2022, using MODIS satellite-derived Land Surface Temperature (LST) data [2].
  • The Urban Heat Island effect poses significant risks to biodiversity, human health, and regional climate systems [2].
  • Strong evidence shows that rising global temperature anomalies increase mortality risk in vulnerable nations [1].
  • Several studies report that climate change can have drastic consequences for animal movements and animal-human interactions [6]. It can also affect arthropod vectors associated with animals [6].
  • When animal patterns and human interactions change, the exposure of humans to zoonotic pathogens potentially carried by wildlife also changes [6]. Approximately 60% of emerging human pathogens and 75% of all emerging infectious diseases are categorized as zoonotic [6].
  • Anthropogenic actions, such as population growth and industrialization, drive the occupation of forest areas and increase contact with wildlife and their associated parasites and vectors [7]. These actions, including deforestation, disrupt the planet's climatic and ecological balance [7].
  • High temperatures, alongside wildfires, floods, and storms, have been observed to amplify human suffering [12].
  • An experimental study on zebrafish (Danio rerio) assessed the interactive effects of water temperature and endocrine-disrupting chemical (EDC) exposure on sexual development and population viability [17]. Water temperatures of 28 °C (current ambient mean spawning temperature) and 33 °C (projected for the year 2100) were used, along with clotrimazole at 2 μg/L and 10 μg/L [17]. This study, however, focused on fish and not reptiles [17].
  • Climate change is identified as a major threat to human health and influences infectious diseases, with significant regional changes in vector and pathogen distribution reported in various regions over recent decades [14].

Methods

The information presented draws from various types of scientific investigations. A theoretical framework was developed to analyze the demographic and economic impacts of rising global temperatures [1]. An observational study investigated the diurnal and seasonal dynamics of Surface Urban Heat Island intensity (SUHII) for 141 Indian cities over two decades (2001-2022) using MODIS satellite-derived Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI), evapotranspiration (ET), and Land Use Land Cover (LULC) data [2].

Several sources are literature reviews or overviews, summarizing existing studies on topics such as the impact of human activities on zoonotic infection transmissions [6], anthropogenic drivers for emerging zoonotic diseases [7], and the impact of climate change on vector-borne diseases [14]. One study involved an experimental approach to disentangle atmospheric and soil drivers of plant functions across scales [3].

Additionally, an experimental study assessed the interactive effects of water temperature and endocrine-disrupting chemical exposure on sexual development and population viability in zebrafish [17].

Interpretation

The supplied sources indicate that urban areas in India are experiencing a notable Urban Heat Island effect, with temperatures 1–4 °C higher than surrounding rural areas, a trend observed over two decades (2001-2022) [2]. This phenomenon, driven by urbanization and regional climate change, is reported to pose significant risks to biodiversity, human health, and regional climate systems [2]. Globally, rising temperatures are associated with increased mortality risk in vulnerable populations [1].

While strong evidence points to the existence of the Urban Heat Island effect in Indian cities and its general risks to biodiversity [2], the specific impact of these rising temperatures on reptiles within urban areas of India is not clearly established in the supplied sources. However, several studies report that climate change can lead to drastic consequences for animal movements, alter animal-human interactions, and affect arthropod vectors [6]. Changes in these interactions can increase human exposure to zoonotic pathogens carried by wildlife [6]. General anthropogenic actions, including population growth, industrialization, and deforestation, are also recognized as drivers impacting wildlife and ecological balance [7].

An experimental study on zebrafish demonstrated that elevated water temperatures, projected for the year 2100, combined with chemical exposure, can affect the sexual development and population viability of this aquatic species [17]. While this highlights a potential mechanism by which temperature can affect some animal populations, its direct applicability to reptiles in urban Indian environments is not discussed in the provided texts [17].

Limitations

A significant limitation is the absence of direct studies specifically investigating the impact of rising temperatures on reptiles in urban areas of India within the provided sources. While the Urban Heat Island effect in Indian cities and its general risks to biodiversity are documented [2], the specific effects on reptile populations or species are not detailed.

Many of the cited sources are preprints [4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18], which means they have not yet undergone full peer review and may be subject to revision. The study on the Urban Heat Island effect in India is an observational analysis based on satellite data [2]. While it provides valuable insights into temperature gradients, it does not detail direct biological impacts on specific animal groups.

General statements about "biodiversity" [2, 9, 16] or "wildlife" [6, 7, 11, 12] cannot be definitively applied to "reptiles" without explicit evidence. The experimental study on zebrafish explores the effects of temperature on an aquatic species [17], but these findings cannot be directly generalized to terrestrial or semi-aquatic reptiles in urban Indian ecosystems without further specific research.

What's next

The identified Urban Heat Island effect in Indian cities necessitates an in-depth understanding of its spatiotemporal patterns and characterization to inform effective adaptation strategies [2]. Given that climate change affects animal movements and human-animal interactions [6], further research could explore how these changes specifically manifest in urban reptile populations in India.

The broader context of anthropogenic actions driving contact with wildlife and affecting ecological balance [7] suggests a need for integrated approaches to manage urban development and conservation. The concept of a "One Health" approach, which addresses social and economic development, climate change, and biodiversity together, has been proposed as a comprehensive response to environmental and health challenges [12]. Such an approach could be valuable in understanding and mitigating the impacts of rising urban temperatures on diverse animal groups, including reptiles, in India.