Role of herpetofauna in human well-being and farmlands

The herpetofauna are pivotal in maintaining environmental stability and resilience as they provide indicators of ecosystem health and contribute to nutrient cycling and therefore support human well-being (Valencia-Aguilar et al. Reference Valencia-Aguilar, Cortés-Gómez and Ruiz-Agudelo2013). The herpetofauna are even important in the medical field (Brozio et al. Reference Brozio, O’Shaughnessy, Woods, Hall-Barrientos, Martin and Kennedy2021). Newts, salamanders and tadpoles of frogs regulate vectors of several disease-carrying microbes (Perrin et al. Reference Perrin, Pellet, Bergonzoli, Christe and Glaizot2023). Of all the services herpetofauna deliver regarding human well-being, they have long been identified as ‘farmers’ friends’ because they improve soil quality and aeration, reduce biogas emissions, help in dispersal of seeds, improve crop health and enhance pollination (Olesen & Valido Reference Olesen and Valido2003, Fang et al. Reference Fang, Yi, Dai, Gao and Cao2019). Amphibians and reptiles are effective bioregulators of crop pests (Monagan et al. Reference Monagan, Morris, Rabosky, Perfecto and Vandermeer2017, Ghosh & Basu Reference Ghosh and Basu2023). Amphibians are major regulators of ground-dwelling pests, while reptiles feed on both ground-dwelling insects and arthropods in flight or at the crop surface (Ghosh & Borzée Reference Ghosh and Borzée2024). Furthermore, snakes also reduce the populations of rodents and other small mammals, thereby benefitting agriculture (Majumder Reference Majumder2022). Additionally, herpetofauna display diverse foraging modes (i.e., active and ambush foraging modes), which have differential impacts on crop pest regulation (Ghosh & Borzée Reference Ghosh and Borzée2024). However, in India, there is very limited information regarding ecosystem service provisioning by farmland herpetofauna (Deuti et al. Reference Deuti, Ganesh, Chandra, Kaur, Batish, Singh and Kohli2022). Thus, considering their important roles in ecosystems (Cogălniceanu et al. Reference Cogălniceanu, Stănescu, Székely, Topliceanu, Losif and Szekely2021), the loss of herpetofauna could have a cascading effect on whole agroecological systems.

Racing towards extinction

India is among the top 15% of regions in the world that could experience a phylogenetic diversity loss of reptiles owing mainly to habitat destruction from agricultural expansion (Cox et al. Reference Cox, Young, Bowles, Fernandez, Marin and Rapacciuolo2022). In India, of 426 amphibian species that have been assessed to date, 310 are endemic (Re:wild et al. 2023). In the Western Ghats of India there is a concentration of 139 threatened amphibian species, with 16 species being Critically Endangered, 72 being Endangered and 51 being Vulnerable (Gohain Reference Gohain2023).

Amphibians and reptiles share common threats, including agriculture, urbanization, tourism, small-holder grazing ranching, mining and quarrying, transportation, fire, invasive species and diseases, of which agriculture is the most severe (Fig. 1a,b; IUCN 2024). Being cold-blooded, herpetofauna have unique physiological demands and therefore narrow tolerances and specific needs for microclimates, rendering them the most vulnerable of the vertebrates (Ghosh & Basu Reference Ghosh and Basu2020). Air humidity, temperature, light intensity and nature of habitat impact the diversity and abundance of herpetofauna, as well as their breeding, spatial activity, foraging, movement, choice of retreat and thermoregulation (Wisler et al. Reference Wisler, Hofer and Arlettaz2009). Moreover, herpetofauna species have small home ranges and low dispersal rates, to the extent that many amphibians are philopatric and only travel a distance of 400 m to a few kilometres in their lifetime (Fonte et al. Reference Fonte, Mayer and Lötters2019, Guiller et al. Reference Guiller, Legentilhomme, Boissinot, Blouin-Demers, Barbraud and Lourdais2022), making them even more sensitive to land-use changes associated with agriculture.

Figure 1.

Illustration of the diverse impacts of agricultural intensification on herpetofauna diversity and their ecosystem services facing similar threats following the International Union for Conservation of Nature (IUCN) categorization system (IUCN 2024): (a) the difference in diversity between low and high agricultural intensification; (b) the trends in pesticide application; (c) the threats listed by IUCN for loss of amphibians; (d) the threats listed by IUCN for loss of reptiles; and (e) photographs showing the change in landscape from low to high agricultural intensification and ecosystem services such as bioregulation of crop pests provided by farmland herpetofauna. All photographs by DG. The threats mentioned here follow the IUCN categorisation system: 1.1 Housing & urban areas; 1.3 Tourism & recreation areas; 2 Agriculture & aquaculture, 2.1.1 Shifting agriculture, 2.1.2 Small-holder farming; 2.1.3 Agro-industry farming; 2.3.2 Small-holder grazing, ranching or farming; 3.2 Mining & quarrying; 4 Transportation & service corridors, 5.1.1 Intentional use (species being assessed is the target), 5.3.3 Unintentional effects: subsistence/small scale (species being assessed is not the target) [harvest], 5.3.4 Unintentional effects: large scale (species being assessed is not the target) [harvest], 5.3.5 Motivation unknown/unrecorded, 7.1.1 Increase in fire frequency/intensity, 8.1 Invasive non-native/alien species/diseases. References in the figure are: ¹Ghosh (Reference Ghosh2021); ²Statista (2024); ³IUCN (2024); ⁴Srivathsa et al. (Reference Srivathsa, Vasudev, Nair, Chakraborti, Chanchanu and Defries2023); ⁵Monagan et al. (Reference Monagan, Morris, Rabosky, Perfecto and Vandermeer2017); ⁶Ghosh and Basu (Reference Ghosh and Basu2023).

Agricultural intensification is manifested through several factors such as excessive use of pesticides and fertilizers, agricultural land conversion, types of cropping systems, cropping intensity, intensity of grazing and the proportion of natural habitat remaining around farmlands at a landscape level, and therefore the pathways through which it affects species are difficult to discern (Concepción et al. Reference Concepción, Moretti, Altermatt, Nobis and Obrist2015, Ghosh & Basu Reference Ghosh and Basu2020). These agricultural factors operate at several spatial and temporal scales, affecting both amphibians and reptiles across their various life-history stages, including their dispersal and range distribution (Arntzen et al. Reference Arntzen, Abrahams, Meilink, Losif and Zuiderwik2017, Guiller et al. Reference Guiller, Legentilhomme, Boissinot, Blouin-Demers, Barbraud and Lourdais2022), and causing a loss of genetic diversity due to reduced gene flow (Gauffre et al. Reference Gauffre, Boissinot, Quiquempois, Leblois, Grillet and Morin2022). Of all these factors, pesticides have been recognized as representing one of the major threats to herpetofauna, causing deformities in amphibians, altering movement patterns in snakes and reducing offspring numbers (Fig. 2a,b; Hopkins et al. Reference Hopkins, Winne and DuRant2005, Guerra & Aráoz Reference Guerra and Aráoz2016, Simbula et al. Reference Simbula, Macale, Gomes, Vignoli and Carretero2021). Despite their detrimental impacts, the use of pesticides is still increasing, with their use projected to increase from 4.30 to 4.41 million tonnes between 2023 and 2027 (Statista 2024). In India, intensive agriculture hosts only half the herpetofaunal diversity of traditional rain-fed agriculture with less pesticide input and more forest cover (Ghosh & Basu Reference Ghosh2021).

Figure 2.

Impacts of pesticide application (e.g., carbofuran and cypermethrin), showing dead (a) a checkered keelback snake and (b) Dicroglossidae and Microhylidae amphibians from rice paddies in India. All photographs by DG.

Can redesigning agricultural landscapes reverse biodiversity loss?

Habitats within farmland such as ponds, drainage ditches, flooded fields and woodlots are regularly used by amphibians and reptiles at various life-history stages and are considered critical for the persistence of local herpetofaunal populations (Boissinot et al. Reference Boissinot, Besnard and Lourdais2019). Conventional agricultural intensification relies on synthetic fertilizers and pesticides (Kremen Reference Kremen2020), which have negative effects on biodiversity and the ecosystem. Ecological intensification, on the other hand, provides greater environmental stability by minimizing these detrimental consequences, supporting natural processes that promote, replenish and regenerate the ecosystem services on which farmers can rely and bringing societal benefits including good water quality and biodiversity conservation (Kremen Reference Kremen2020, Mondal & Palit Reference Mondal, Palit, Jhariya, Meena and Banerjee2021). Pollinators and natural crop pest predators positively respond to ecological intensification (Garibaldi et al. Reference Garibaldi, Steffan-Dewenter, Kremen, Morales, Bommarc and Cunningham2011). In California, ecological intensification increased the species richness and functional diversity of specialized and rare species of native bees and birds (M’Gonigle et al. Reference M’Gonigle, Ponisio, Cutler and Kremen2015), including several threatened ones (Kross et al. Reference Kross, Martinico, Bourbour, Townsend, McColl and Kelsey2020). In India, ecological intensification has also been shown to improve rice quality and yields (Kumar et al. Reference Kumar, Singh, Kumar, Ray and Dash2023).

Ecological intensification can be achieved by either improving heterogeneity in agricultural landscapes through diversifying crop types (higher compositional heterogeneity) or through improving the spatial heterogeneity of the cropped areas by increasing the diversity and spatial pattern complexity of arable land-cover types (configurational heterogeneity; Fahrig et al. Reference Fahrig, Baudry, Brotons, Burel, Crist, Fuller and Sirami2011). Higher crop diversity provides greater resources for different species, thus increasing biodiversity (Novotný et al. Reference Novotný, Zapletal, Kepka, Benes and Konvicka2015), as has been seen for birds, plants and different arthropod groups (Fahrig et al. Reference Fahrig, Girard, Duro, Pasher, Smith and Javorek2015).

Another strategy for increasing landscape heterogeneity is through promoting and maintaining hedgerow landscapes. Hedgerow networks are amalgamations of natural and anthropized habitats that connect diverse habitats to a greater extent than purely agricultural landscapes and are thus favourable to natural biodiversity (Boissinot et al. Reference Boissinot, Besnard and Lourdais2019). Hedgerows improve ecosystem services through pest control and pollination (Kremen Reference Kremen2020). Microhabitat quality is also dependent on the hedgerow structure and presence of herbaceous borders, which positively affect biodiversity (Graham et al. Reference Graham, Gaulton, Gerard and Staley2018). The hedgerow landscape is important for the biodiversity of several groups (Fig. 3a; insects, Chamberlain et al. Reference Chamberlain, Fuller, Bunce, Duckworth and Shrubb2000; rodents, de la Peña et al. Reference de la Peña, Butet, Delettre, Paillat, Morant, Du and Burel2003; birds, Cornulier et al. Reference Cornulier, Robinson, Elston, Lambin, Sutherland and Benton2011; amphibians, Arntzen et al. Reference Arntzen, Abrahams, Meilink, Losif and Zuiderwik2017). Reptiles also occupy hedgerows, forest edges and other anthropic habitats such as stone walls (Martinez-Freiria et al. Reference Martinez-Freiria, Lorenzo and Lizana2019). Such linear habitats offer multiple benefits, including microhabitats for thermoregulation and hydroregulation and the provision of shelter and food (Guillon et al. Reference Guillon, Guiller, DeNardo and Lourdais2014). These linear habitats also facilitate dispersion and thus connectivity between populations and offer breeding sites (Arntzen et al. Reference Arntzen, Abrahams, Meilink, Losif and Zuiderwik2017).

Figure 3.

Examples of (a) hedgerows positively influencing crop yields while improving ecosystem services and biodiversity in farmlands (adapted from Kremen Reference Kremen2020) and (b) a landscape in India that shows connectivity with diverse landscapes such as forests and water bodies and the presence of linear strips of native plants in rice paddies as an indication of how farmlands can be redesigned (image created using Google Earth Pro, version 7.3.6.9796). ¹Kremen (Reference Kremen2020).

Different vegetation types enhance diversity at a regional level (Michael et al. Reference Michael, Cunningham, Donnelly and Lindenmayer2012). Plants impact amphibians by affecting abiotic factors such as resource quality and the nature and strength of interspecific interactions between amphibians and other species such as predators and their abundance (Burrow & Maerz Reference Burrow and Maerz2022). Reptile diversity increases with greater native plant species in farmlands. Thus, hedgerow landscapes consisting of complex mosaics of pastures, ponds and hedges connected to forest patches could effectively reverse the loss of farmland herpetofauna in India (Fig. 3b).

The importance of hedgerows in India was tested between 1994 and 2001. North-east India is an excellent case that demonstrates the importance of hedgerows (Sundriyal Reference Sundriyal2003). Developing hedgerows incurred initial costs due to the procuring of the seeds of hedgerow species and the establishment and maintenance of hedgerows but provided consistent profits in the following years and increased major crop yields by 1.5–3.0% (Sundriyal Reference Sundriyal2003). The impact on crops has been seen to be more significant for vegetable and root crops. Hedgerows of Jum cultivation have also been reported to contribute significantly to reductions in nutrient runoff and soil erosion (Sundriyal Reference Sundriyal2003). Therefore, establishing hedgerows would require selecting species that are fast-growing, that require minimal inputs while producing high biomass and that contribute to ecosystem services including nitrogen fixation and preventing soil erosion. Low costs would be incurred to create and maintain hedgerow landscapes while also increasing profits.

The uptake of ecological intensification from science to practice is still rather limited. It is estimated that 29% of all farms worldwide have integrated some form of ecological intensification (Pretty Reference Pretty2018). Of the total land area in India, only 46% is available as cultivable land, with more than 250 cropping systems and cereal cultivation accounting for c. 75% of the cultivatable land (Hobbs & Gupta Reference Hobbs, Gupta, Kijne, Barker and Molden2003). As per the Government of India (2015) report, the small and marginal landholding farmers, dominated by Scheduled Castes and Scheduled Tribes and accounting for c. 85% of the total agricultural landholders, cultivate over 72 million hectares of land and contribute 50–60% of India’s total food requirement (Nath et al. Reference Nath, Lal, Sileshi and Das2018). Therefore, alongside improving food security and preventing natural resource depletion, in India ecological intensification needs to consider farmers’ socio-economic status as well. Adoption of this approach would require awareness to be generated within the farming community and convincing of local non-governmental organizations to implement these technologies, which could prove to be an effective strategy (Sundriyal Reference Sundriyal2003).