Impact statement
By integrating global change, extinction debt, and long-term evidence from the Western Himalaya, this study demonstrates how species persistence can conceal hidden biodiversity erosion and provides a framework for identifying populations at risk before local extirpations occur.
Introduction
The Himalaya, especially the Indian Western Himalaya (Jammu and Kashmir, Ladakh, Himachal Pradesh and Uttarakhand), is a biodiversity hotspot for medium-large mammals (>3 kg; Cardillo et al., Reference Cardillo, Mace, Jones, Bielby, Bininda-Emonds, Sechrest, Orme and Purvis2005). This region has at least 20 native ungulates; at least 8 are Caprids, 7 Cervids, 3 Bovids, 1 Equid, and 1 Suid. Besides, at least 9 felid and 5 canid species are found here (Sharma et al., Reference Sharma, Kamalakannan and Venkataraman2015). It spans eight major mountain ecoregions, from subtropical broadleaf forests to alpine meadows and the cold deserts, contributing to one of the highest levels of ecological heterogeneity in Asia (Olson et al., Reference Olson, Dinerstein, Wikramanayake, Burgess, Powell, Underwood, D’amico, Itoua, Strand, Morrison, Loucks, Allnutt, Ricketts, Kura, Lamoreux, Wettengel, Hedao and Kassem2001). Elevation gradients here go from near sea level to >7,000 m, connecting various levels of the Himalayas into the Tibetan Plateau.
Interestingly, the same historical and biogeographic processes that generated this diversity have also produced communities characterised by small, isolated, and peripheral populations. The exceptional mammalian diversity of the Western Himalaya is the product of a complex geological and biogeographic history (Feijó et al., Reference Feijó, Ge, Wen, Cheng, Xia, Patterson and Yang2022; Saxena and Rao, Reference Saxena and Rao2024). The uplift of the Himalayan mountain chain created steep environmental gradients and promoted diversification through geographic isolation, while repeated Pleistocene climatic oscillations reshaped species distributions and left many populations confined to glacial refugia and peripheral range margins (Sharma and Hope, Reference Sharma and Hope2026). Situated at the confluence of the Palearctic and Indomalayan biogeographic realms, the region supports a melange of cold-adapted alpine specialists, temperate forest species, and subtropical taxa within a small area (Olson et al., Reference Olson, Dinerstein, Wikramanayake, Burgess, Powell, Underwood, D’amico, Itoua, Strand, Morrison, Loucks, Allnutt, Ricketts, Kura, Lamoreux, Wettengel, Hedao and Kassem2001). However, this evolutionary legacy has resulted in populations being small, fragmented, and located at the edge of their global distributions (Hampe and Petit, Reference Hampe and Petit2005). These characteristics, which once reflected historical processes of colonisation and persistence, may now increase vulnerability to contemporary global change, transforming a historical source of biodiversity into a driver of extinction risk.
Although extinctions are often perceived as abrupt events, they are typically preceded by prolonged ecological changes that may remain undetected. Concepts like extinction debt, range-edge vulnerability, biotic homogenisation and the extinction vortex highlight that populations can persist long after the processes driving their decline have begun. Extinction debt is the delayed loss of species or populations following habitat or environmental changes (Kuussaari et al., Reference Kuussaari, Bommarco, Heikkinen, Helm, Krauss, Lindborg, Öckinger, Pärtel, Pino, Rodà, Stefanescu, Teder, Zobel and Steffan-Dewenter2009). Range-edge vulnerability refers to the heightened susceptibility of populations occurring at the periphery of a species’ distribution (Hampe and Petit, Reference Hampe and Petit2005). Biotic homogenisation is when distinct biological communities become more similar to each other (Wayman et al., Reference Wayman, Sadler, Martin, Graham, White, Tobias and Matthews2024). Finally, the extinction vortex describes how declining populations can trigger mutually reinforcing demographic, genetic, behavioural, and environmental processes that accelerate their path towards extinction (Gilpin and Soulé, Reference Gilpin, Soulé and Soulé1986; Fagan and Holmes, Reference Fagan and Holmes2006).
In mountain ecosystems, climate change and anthropogenic disturbance may not immediately eliminate species but instead alter demographic and ecological processes by reducing recruitment, limiting dispersal, compressing habitat, and facilitating the expansion of more adaptable competitors into previously distinct ecological niches (Dirnböck et al., Reference Dirnböck, Essl and Rabitsch2011). Consequently, communities may retain much of their apparent species richness while undergoing profound ecological restructuring, including loss of ecosystem functions and services, creating an illusion of stability despite increasing extinction risk. These subtle changes suggest that the earliest signals of biodiversity loss are often expressed through shifts in species interactions, demographic stagnation, and changing community composition rather than through immediate local extirpation (Valiente-Banuet et al., Reference Valiente-Banuet, Aizen, Alcántara, Arroyo, Cocucci, Galetti, García, García, Gómez, Jordano, Medel, Navarro, Obeso, Oviedo, Ramírez, Rey, Traveset, Verdú and Zamora2015). Although extinction is fundamentally an ecological process, conservation is a political endeavour, making it crucial to safeguard these populations within national boundaries, even though they may be present in sufficient numbers in other countries, to prevent irreversible local loss.
Therefore, we argue that the Western Himalaya is in a phase of deceptive diversity (Figure 1). Deceptive diversity does not replace the concept of extinction debt; rather, it describes the ecological state during which extinction debt may accumulate but remains concealed because species continue to persist. Whereas extinction debt refers to future biodiversity loss resulting from past environmental change (Kuussaari et al., Reference Kuussaari, Bommarco, Heikkinen, Helm, Krauss, Lindborg, Öckinger, Pärtel, Pino, Rodà, Stefanescu, Teder, Zobel and Steffan-Dewenter2009), deceptive diversity focuses on the present-day erosion of demographic, ecological and genetic resilience that precedes, and may or may not ultimately generate, that delayed extinction. Recognising these signals before species disappear provides an opportunity to anticipate biodiversity loss and guide conservation. Both stochastic and deterministic processes can cause eventual extinctions. This can be particularly important in small habitat remnants, where both abiotic and biotic edge effects can cause gradual deterioration of habitat quality (Harper et al., Reference Harper, Macdonald, Burton, Chen, Brosofske, Saunders, Euskirchen, Roberts, Jaiteh and Esseen2005). The deception we refer to is not a formal measure of species diversity, but the widespread use of species presence, occupancy or richness as indicators of conservation status. Many biodiversity assessments implicitly equate continued species occurrence with ecological security, whereas our examples show that species can remain present while demographic viability could progressively erode.
Global change as a driver of deceptive diversity, eventually accumulating extinction debt, in the Western Himalaya. Climate change and accelerating infrastructure development interact to compress habitats, increase fragmentation, facilitate novel species interactions, and reduce connectivity among naturally small and isolated range-edge populations. These processes diminish demographic resilience and adaptive capacity while species remain present, generating an extinction debt that may remain undetected until local extirpations occur. [Digitally illustrated by Manini Bansal originally for this manuscript].
Figure 1. Long description
A large digital illustration titled Deceptive Diversity in the Western Himalaya.
At the top, a landscape shows a mountain range transitioning from lush green forests on the left to developed slopes with roads, dams, solar panels, and wind turbines on the right.
On the far left, a Drivers column lists Climate Change (rising temperatures, altered snowfall, upward shift of treelines, extreme events) and Development Pressures (roads, tourism, livestock, energy projects).
In the center, six numbered panels describe Ecological Mechanisms Under Global Change:
1. Habitat Compression and Loss: Arrows show treelines moving up toward mountain peaks.
2. Novel Interactions Between Species: A snow leopard, a smaller cat, and a mountain goat are shown together.
3. Increased Fragmentation: A road cuts through a mountain valley.
4. Reduced Connectivity and Dispersal: A map-like graphic shows isolated habitat patches with red X marks on connecting paths.
5. Lower Recruitment and Population: An adult and juvenile mountain goat stand on barren ground.
6. Demographic Stochasticity: A line graph shows a jagged downward trend in population size.
A blue horizontal bar below these panels states that deceptive diversity contributes to extinction debt where species richness appears unchanged but underlying risks increase. A box on the right notes the underlying reality includes altered species composition, silent demographic declines, increasing vulnerability, and loss of ecological resilience.
On the far right, an Outcomes Over Time column lists local extinctions, biotic homogenisation, loss of ecosystem functions, and reduced adaptive capacity.
At the bottom, a final section titled How We Respond Matters emphasizes proactive conservation and sustainable development.
Small, fragmented, peripheral populations
The conservation importance of peripheral populations has become increasingly debated. Classical theory suggested that populations at the edge of a species’ distribution are vulnerable because they are often small, isolated and subject to reduced gene flow, making them susceptible to demographic and genetic stochasticity (Hampe and Petit, Reference Hampe and Petit2005; Eckert et al., Reference Eckert, Samis and Lougheed2008). However, more recent syntheses demonstrate that this pattern is not universal. Many range-edge populations harbour unique genetic diversity, exhibit strong local adaptation, and can contribute disproportionately to a species’ evolutionary potential under environmental change (Rehm et al., Reference Rehm, Olivas, Stroud and Feeley2015; Pironon et al., Reference Pironon, Papuga, Villellas, Angert, García and Thompson2017). Thus, geographic position alone is a poor predictor of extinction risk. Instead, vulnerability arises where peripheral populations are simultaneously small, fragmented and demographically isolated. This distinction is particularly relevant in the Western Himalaya, where many mammals represent the sole populations occurring within India. Hangul (Cervus hanglu hanglu), Ladakh urial (Ovis vignei vignei), Markhor (Capra falconeri) and Woolly flying squirrel (Eupetaurus cinereus), all occur as geographically restricted peripheral populations that are isolated from the core of their global distributions (Figure 2). Species like Tibetan gazelle (Procapra picticaudata), Wild Yak (Bos mutus) and Tibetan antelope (Pantholops hodgsonii) occupy only a small portion of their broader range within India, with widespread distribution in neighbouring China; loss of these populations would constitute irreversible local extirpations from India.
Map showing select species exhibiting fragmented populations in the Western Indian Himalaya.
Figure 2. Long description
A topographical map with a coordinate grid from 31.000 degrees North to 35.000 degrees North and 74.000 degrees East to 79.000 degrees East. The terrain is color-coded by elevation, with dark green representing lowlands, brown representing mid-elevations, and white representing high-altitude snow-covered peaks.
Four species ranges are marked with colored outlines:
* Wooly Flying Squirrel: Two small, isolated blue-outlined areas. One is in the Northwest near 34.5 degrees North, and the other is in the Southeast near 31.5 degrees North.
* Markhor: Several light blue-outlined fragments concentrated in the West and Southwest, primarily along the transition from green to brown terrain.
* Hangul: A small cluster of green-outlined circles located in the West-Central region near 34.0 degrees North.
* Ladakh Urial: A series of pink-outlined polygons concentrated in the North-Central and Northeast regions, situated within the high-elevation white and brown zones.
A legend in the bottom right identifies the species and elevation scale. A scale bar at the bottom left indicates 0 to 200 k m. A North arrow is located in the top right corner.
Furthermore, population stagnation may be an early indicator of extinction debt. Although populations remain extant and may appear numerically stable, prolonged absence of population growth often reflects underlying demographic constraints, including reduced recruitment, limited dispersal, low genetic diversity, and diminished resilience to environmental change. Stable abundance should not necessarily be interpreted as favourable conservation status, but rather as a potential lag phase during which extinction debt accumulates before eventual population decline becomes evident (Tilman et al., Reference Tilman, May, Lehman and Nowak1995; Kuussaari et al., Reference Kuussaari, Bommarco, Heikkinen, Helm, Krauss, Lindborg, Öckinger, Pärtel, Pino, Rodà, Stefanescu, Teder, Zobel and Steffan-Dewenter2009; Falaschi et al., Reference Falaschi, Lo Parrino, Manenti and Ficetola2025).
Hangul are found only in a small population of <200 individuals restricted to 808 km2, with intense concentration in the 141 km2 Dachigam National Park (Ahmad et al., Reference Ahmad, Mirelli, Charoo, Nigam, Qureshi, Naqash and Focardi2023), a drop from nearly 3,000 individuals in the 1900s (Srivastava and Vasudevan, Reference Srivastava and Vasudevan2022). Over 20 years of monitoring revealed that despite strict protection and available habitat in and around Dachigam, the hangul population fails to increase in size. In fact, population viability analysis found that further population decrease is likely (Ahmad et al., Reference Ahmad, Mirelli, Charoo, Nigam, Qureshi, Naqash and Focardi2023). Similarly, Markhor in the Western Himalaya, the sole population in India, remains at less than 400 individuals. Their distribution has shrunk from c.300 km2 in the late 1940s to less than 120 km2, with near extirpation from the Hirpora region recently (Bhatnagar et al., Reference Bhatnagar, Ahmad, Kyarong, Ranjitsinh, Seth, Lone, Easa, Kaul and Raghunath2009; Hussain et al., Reference Hussain, Lone, Tak and Bhat2026). This is in contrast to the Markhor population in Pakistan’s Karakorum and Hindu-Kush mountains and Tajikistan’s Pamir range, where the population has shown recoveries from historic lows to now, harbouring over 7,000 individuals each (Ahmad et al., Reference Ahmad, Rehman, Ali, Din, Haider, Din and Nawaz2022; Akramov et al., Reference Akramov, Najmiddinov, Ghoddousi, Khanyari, Moheb, Sepahvand, Bhatnagar and Herrero2022). Ladakh urial, which are restricted to Ladakh in India, were found to use only 32% (CI: 16–53%) of their presumed range (Khara et al., Reference Khara, Khanyari, Ghoshal, Rathore, Pawar, Bhatnagar and Suryawanshi2021). Additionally, two population estimation exercises in Western Ladakh, an area consisting majority of the remaining urial population across Ladakh, showed no discernible increase in population despite seven years gap – 686 (CI: 686–767) urial in 2018 and 740 (CI: 609–1,246) urial in 2025 (z-score = 0.125; p = 0.9) (Khara et al., Reference Khara, Khanyari, Ghoshal, Rathore, Pawar, Bhatnagar and Suryawanshi2021; NCF Urial Report, 2026). While this result does not show population increase, they are insufficient on its own to infer demographic stagnation or extinction debt, highlighting the need for long-term monitoring of recruitment, survival, and age structure to determine whether the population is stable, cyclic, or experiencing underlying demographic constraints. Tibetan Gazelle range has contracted from c.20,000 km2 in the early 1900s to <50 km2 on the Kalak-Tartar (KTT) plateau in Ladakh (although they also inhabit a small region in Tso Lhamo in Eastern Himalaya, Sikkim). Community monitoring of the KTT by two villagers from Hanle (nearest village to KTT) consistently recorded <60 individuals from KTT between 2008–2014, a trend that has persisted till now (Ghoshal, Reference Ghoshal2019). This is in sharp contrast to neighbouring China’s high plateau regions, which harbour a near-contiguous distribution of Tibetan gazelle population consisting of >100,000 individuals (Jiang et al., Reference Jiang, Li, Qin, Zhang, Lin, Cai, Gao and Zhang2019). Similarly, wild yak and Tibetan antelope persist as small, fragmented, and largely transboundary populations restricted to eastern Ladakh at the southwestern edge of their global distributions, with only ~200–225 wild yaks and a seasonal, male-dominated Tibetan antelope population of ~700 individuals recorded in the Chang Chenmo Valley (Ahmad et al., Reference Ahmad, Nigam and Suhail2026). In contrast, these species remain widespread across the Tibetan Plateau in China, where c.22,000 wild yaks and >300,000 Tibetan antelope occupy extensive, connected landscapes, underscoring the demographic vulnerability of their peripheral Indian populations (Du et al., Reference Du, Zou, Xu, Guo, Li, Zhang, Su, Ma and Guo2016; Shi et al., Reference Shi, Guo, Engelhardt, Weladji, Zhou, Long and Meng2016). The Woolly flying squirrel has a highly restricted and fragmented distribution, with records limited to a few scattered locations in the Western Himalaya (Pal et al., Reference Pal, Thakur, Bhattacharya and Sathyakumar2019; Mueen et al., Reference Mueen, Thuktan, Khanyari and Khaleel2024). Eurasian Lynx (Lynx lynx) and Pallas’ Cat (Otocolobus manul) exhibit similar distribution from small patches across the Western Himalayas (Pal et al., Reference Pal, Thakur, Arya, Bhattacharya and Sathyakumar2021; Sharma et al., Reference Sharma, Thuktan, Tobge, Angrup, Chhering, Sherab, Chhering, Bajaj, Khanyari and Suryawanshi2024).
The demographic vulnerability of many western Himalayan mammals is increasingly reflected in their genetic structure. For example, the endemic Hangul exhibits markedly low genetic diversity compared to other red deer of the world (Mukesh et al., Reference Mukesh, Kumar, Sharma, Shukla and Sathyakumar2015). Kashmir musk deer (Moschus cupreus) exhibit population subdivision, restricted gene flow, and reduced genetic diversity associated with long-term isolation and habitat fragmentation (Sharief et al., Reference Sharief, Singh, Kumar, Singh, Ghosh, Joshi, Ramesh, Thakur and Sharma2025). Snow leopards, a key predator, are similarly constrained. Ladakh alone holds about 50% of India’s snow leopards (Raina et al., Reference Raina, Mungi, Kumar, Rathi, Khan, Patel, Bhasin, Bisht, Hiby, Pandav, Sultan, Takpa and Jhala2025). Solari et al. (Reference Solari, Morgan, Poyarkov, Weckworth, Samelius, Sharma, Ostrowski, Ramakrishnan, Kubanychbekov, Kachel, Johansson, Lkhagvajav, Hemmingmoore, Alexandrov, Bayaraa, Grachev, Korablev, Hernandez-Blanco, Munkhtsog, Rosenbaum, Rozhnov, Madad Rajabi, Noori, Suryawanshi, Armstrong and Petrov2025) show that snow leopards suffer from historically low genetic variation. This, along with a modest population size, leaves limited capacity to buffer against future anthropogenic pressures, suggesting that their persistence may be more tenuous than numbers imply.
These examples suggest that the Western Himalaya may be illustrating deceptive diversity. Many of the region’s mammals occur as naturally small, fragmented, and isolated peripheral populations, rendering them disproportionately vulnerable to climate change, habitat fragmentation, and stochastic events (Hampe and Petit, Reference Hampe and Petit2005). As a consequence, stable occupancy or persistence should not be equated with population security, particularly where abundance has stagnated, and genetic diversity is declining. These patterns are characteristic of an emerging extinction debt (Collen et al., Reference Collen, Bykova, Ling, Milner-Gulland and Purvis2006).
Global change: Accelerating the erosion of peripheral, small, and fragmented populations?
The concept of global change emphasises the interactions between climate-driven redistribution of biodiversity and development-driven restriction of movement, highlighting how adaptation to one driver is increasingly constrained by another (Oliver and Morecroft, Reference Oliver and Morecroft2014).
Mountain ecosystems are among the most climate-sensitive regions on Earth, with warming occurring more rapidly than the global average in many high-elevation systems (Pepin et al., Reference Pepin, Bradley, Diaz, Baraer, Caceres and Forsythe2015). Jammu and Kashmir has warmed by up to nearly 1 °C in the last two decades (Gopikrishnan et al., Reference Gopikrishnan, Kuttippurath and Chandran2026). Recent glacier mass-balance estimates from western Ladakh demonstrate that glacier retreat in the trans-Himalaya is occurring at rates comparable to some of the world’s best-known climate-change hotspots such as the European Alps and Alaska (Mandal et al., Reference Mandal, Vishwakarma, Angchuk, Azam, Garg and Soheb2024). Simultaneously, the Western Himalaya, like many mountain regions, is experiencing unprecedented expansion of roads, hydropower, tourism, mining, military infrastructure, and urbanisation, exposing previously remote landscapes to increasing anthropogenic pressures Chakraborty, Reference Chakraborty2021). Jammu-Kashmir and Himachal Pradesh have over 15 M-dams under construction (Central Electricity Authority [CEA], 2025). Alongside, Government of India plans propose approximately 10 GW of utility-scale solar capacity (13 GW including wind), requiring nearly 500 km2 of land in Changthang together with extensive transmission infrastructure, roads, and substations, potentially transforming one of India’s most intact high-altitude ecosystems (Rathore, Reference Rathore and Zargar2024). The pace of infrastructure expansion in the Western Himalaya has been further accelerated by recent policy changes, including the exemption of highway projects within 100 km of India’s international borders from prior environmental clearance under the Environmental Impact Assessment Notification (MoEFCC, 2022).
These facets of global change result in habitat compression of species. Climate warming is facilitating the upward advance of treelines and shrub encroachment across the Western Himalaya, progressively replacing alpine grasslands with woody vegetation and reducing the extent of open habitats that support many high-altitude endemic mammals (Schickhoff et al., Reference Schickhoff, Bobrowski, Böhner, Bürzle, Chaudhary, Gerlitz, Lange, Muller, Scholten, Schwab, Singh, Schickhoff and Mal2016; Hamid et al., Reference Hamid, Khuroo, Malik, Ahmad, Singh, Dolezal and Haq2020). As temperatures increase, many cold-adapted species are expected to shift their distributions upslope in pursuit of suitable climatic conditions. However, mountains provide finite elevational space. For species already occupying alpine environments or the highest elevations, opportunities for further upward expansion become increasingly limited, creating the well-recognised “escalator to extinction” phenomenon (Urban, Reference Urban2018).
Simultaneously, warming facilitates the upward expansion of lower-elevation species, increasing the likelihood of novel ecological interactions, competition, and predation in ecosystems that have historically remained relatively isolated. Global change is thus creating novel ecological interactions. Evidence for these is increasingly apparent in the Western Himalaya, particularly seen between two state-wide population estimation exercises for snow leopards in Himachal Pradesh (the first was between 2017–2019 and the second between 2023–2024) (Suryawanshi et al., Reference Suryawanshi, Reddy, Sharma, Khanyari, Bijoor, Rathore, Jaggi, Khara, Malgaonkar, Ghoshal, Patel and Mishra2021; Anon, 2025). In the first round of camera trapping, 31 camera traps were placed in the Upper Kinnaur region covering 484 km2 in March–May 2018. No common leopards (Panthera pardus), a low-elevation-adapted species, were recorded during this survey. However, in the second round of camera trapping (March–May 2024), the same 31 locations were covered and recorded common leopards in at least 3 camera traps. Similarly, the Lahaul region had no previous records of common leopard, including in our camera trapping survey there in May–August 2018 using 97 cameras and covering c. 2,000 km2. However, in 2024 (October–December), using fewer cameras (n = 62), we covered a larger area and recorded common leopards for the first time in Lahaul (from Beeling, which was also surveyed in 2018). While the timing of the two surveys differed, discussions with villagers and Forest Department officials confirmed the photographs from 2024 to be the first evidence of common leopards in the region. While more data and analysis is needed to understand if truly common leopards are moving into snow leopard habitat and what the consequences of this are for both, there is certainly mounting evidence for it. As common leopards have broader dietary niches, higher reproductive rates, and are larger, their expansion into alpine landscapes may intensify competition for shared prey, alter predator guild structure and increase spatial displacement of snow leopards.
Similar upward range expansions have been documented for numerous mountain taxa worldwide driven by global change (Lenoir and Svenning, Reference Lenoir and Svenning2015; Chen et al., Reference Chen, Lenoir and Chen2025). While such range shifts may initially increase local species richness, they may simultaneously intensify competition, alter predator–prey dynamics, facilitate pathogen transmission, and reduce the ecological distinctiveness of high-altitude communities. Consequently, apparent increases in biodiversity may obscure the gradual replacement of cold-adapted specialists by more generalist species.
Climate-driven changes are occurring alongside rapid socioeconomic transformation throughout the Western Himalaya. The expansion of roads, coupled with rapid tourism growth and rising waste accumulation, is a pervasive driver of habitat fragmentation, disrupting landscape connectivity, increasing wildlife mortality, and facilitating the spread of invasive species (Forman and Alexander, Reference Forman and Alexander1998). One of the consequences of this has been the rapid expansion of free-ranging dogs in these landscapes. Admixture between Himalayan wolves and domestic dogs has been detected using molecular markers (Shrotriya et al., Reference Shrotriya, Lyngdoh and Habib2012; Werhahn et al., Reference Werhahn, Liu, Meng, Cheng, Lu, Atzeni, Deng, Kun, Shao, Lu, Joshi, Man Sherchan, Karmacharya, Kumari Chaudhary, Kusi, Weckworth, Kachel, Rosen, Kubanychbekov, Karimov, Kaden, Ghazali, Macdonald, Sillero-Zubiri and Senn2020), and there are several confirmed dog-wolf hybrids across the western Himalayas, particularly in Ladakh (Popescu, Reference Popescu2026). This is worrying, as evidence shows that the Himalayan wolf merits taxonomic recognition as an evolutionarily significant unit (Werhahn et al., Reference Werhahn, Liu, Meng, Cheng, Lu, Atzeni, Deng, Kun, Shao, Lu, Joshi, Man Sherchan, Karmacharya, Kumari Chaudhary, Kusi, Weckworth, Kachel, Rosen, Kubanychbekov, Karimov, Kaden, Ghazali, Macdonald, Sillero-Zubiri and Senn2020). Genetic introgression of this kind is a demonstration of deceptive diversity. The wolf would remain present and detected in surveys, while the genomic distinctiveness that makes it a unique conservation unit is lost. No richness- or presence-based assessment would notice this loss. Besides, dogs harbour the potential to transmit fatal diseases like rabies and Canine Distemper Virus to rare and vulnerable wildlife like snow leopards (Home et al., Reference Home, Bijoor, Bhatnagar and Vanak2022).
Importantly, climate change and development rarely operate in isolation. As species attempt to track suitable climates, dispersal pathways increasingly intersect with human land use (Chen et al., Reference Chen, Hill, Ohlemüller, Roy and Thomas2011). The result is not simply habitat loss, but a reduction in the capacity of populations to respond adaptively to environmental change (Heller and Zavaleta, Reference Heller and Zavaleta2009). This interaction may be severe for the Western Himalaya because many endemic or peripheral populations are already confined to isolated regions with limited opportunities for natural recolonisation.
Ways forward
The interaction of global change acting on fragmented, peripheral and stagnant populations is likely to reinforce the phenomenon of deceptive diversity, leading to unaccounted extinction debt. Populations may persist while recruitment declines, habitat shrinks, connectivity erodes, and ecological interactions are reorganised, especially as the Western Himalaya lacks long-term datasets to investigate such nuances (Rai et al., Reference Rai, Devy, Ganesh, Ganesan, Setty, Hiremath, Khaling and Rajan2021). Recognising deceptive diversity and extinction debt requires a fundamental shift in how biodiversity is monitored and assessed in mountain ecosystems. Species inventories, occupancy estimates, and distribution maps remain essential, but provide an incomplete picture of conservation status when populations can persist despite declining demographic resilience. Detecting hidden biodiversity erosion will require sustained investment in long-term ecological monitoring capable of distinguishing transient fluctuations from directional change. Alongside, studies that quantify the demographic processes underpinning population persistence, including age and sex structure, recruitment, survival, population growth, and the environmental drivers influencing these rates, are needed. Equally important is expanding the use of population genomics and landscape genetics to identify the imprints of global change, like declining connectivity, reduced gene flow, and erosion of adaptive variation before this results in species loss. Together, these approaches will enable conservation to move beyond simply documenting how many species occur in a landscape towards understanding whether populations remain viable, connected, and capable of adapting to a rapidly changing world. By shifting attention from species persistence to population resilience, we can identify the earliest warning signs of biodiversity erosion and intervene before deceptive diversity gives way to irreversible local extirpation.
Open peer review
To view the open peer review materials for this article, please visit http://doi.org/10.1017/ext.2026.10027.
Acknowledgements
Special thanks to the Wildlife Department of Himachal Pradesh, Jammu and Kashmir, Ladakh and Uttarakhand.
Author contributions
Munib and Kulbhushansingh led the conceptualization of the paper with critical inputs from Deepti. Munib led the writing of the draft with major inputs on structure and content by Deepti. Manjot, Shahid and Herman led the gathering of information and gave critical comments on the draft.
Data availability statement
There is no data associated with this manuscript.
Funding statement
This work would not have been possible without the support of Snow Leopard Trust, National Geographic Society, Royal Enfield Social Mission – RESM, ICICI Foundation and Cholamandalam Investment and Finance Company. Munib Khanyari is also funded by the European Union (ERC, CONDJUST, 101054259). Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. This work contributes to ICTA-UAB “María de Maeztu” Programme for Units of Excellence of the Spanish Ministry of Science and Innovation (CEX2024-001506-M/funded by MICIU/AEI/ 10.13039/501100011033).
Open access
Comments
Dear Editors,
Please find attached our manuscript entitled “Deceptive diversity: Mammals in the Indian Western Himalaya face extinction debt due to global change ” for consideration as a Perspective Article in Cambridge Prisms: Extinction.
The Western Himalaya supports one of the world’s most distinctive mountain mammal assemblages, yet many species persist as small, fragmented, and isolated populations that appear stable despite increasing ecological pressures. In this manuscript, we synthesise evidence from long-term population monitoring, distributional studies, genetics, and recent observations of climate and development driven ecological change to argue that biodiversity assessments based solely on species presence or richness may overlook early warning signs of decline. We introduce the concept of deceptive diversity as a framework for describing the period during which populations remain present while the demographic, ecological, and genetic processes necessary for long-term persistence progressively erode, potentially leading to the accumulation of extinction debt.
Rather than documenting extinctions after they occur, our review advocates for detecting the hidden processes that precede biodiversity loss. We discuss how interacting climate and development pressures, i.e. global change, limits the ability of mountain species to respond to environmental change and illustrate these ideas using examples from the Western Himalaya. Although centered on this region, we argue that the framework has broader relevance for mountain ecosystems worldwide where species persistence may mask declining population resilience.
We believe this manuscript is well suited to Prisms: Extinction because it combines empirical evidence with conceptual synthesis to address a central challenge in extinction science, recognizing biodiversity loss before local extirpations occur. We hope the paper will stimulate discussion on how extinction risk is assessed and encourage greater emphasis on long-term demographic, genetic, and ecological monitoring in conservation.
This manuscript is original, has not been published previously, and is not under consideration elsewhere. All authors have approved the manuscript and have no conflicts of interest to declare.
Thank you for your consideration. We look forward to hearing from you.
Sincerely,
Munib Khanyari
On behalf of all co-authors