Land-use change and rising elevation are reshaping spider communities in the north-western Indian Himalayas, with consequences that could ripple across fragile mountain ecosystems, according to new research published in Insect Conservation and Diversity.
Scientists from the Wildlife Institute of India examined spider assemblages across forests, agricultural lands and human-dominated areas along an elevational gradient from 1,500 to 4,500 metres in Himachal Pradesh. Their findings suggest that biodiversity in the Himalayas may be shifting toward functional regimes with lower resilience.
Unlike simple species counts, the study focused on functional diversity the range of ecological roles species perform. Spiders are both predators and prey, consuming vast numbers of insects and helping regulate pest populations and disease vectors. When functional diversity declines, ecosystems lose redundancy: fewer species are available to compensate if others disappear.
The researchers recorded 126 spider species across 26 families. However, species richness and functional diversity generally declined with altitude, with the transition zone between 3,000 and 3,500 metres near the Himalayan treeline emerging as a critical ecological threshold. At higher elevations, reduced functional redundancy means communities may be more vulnerable to environmental stress and climate shifts.
Agricultural landscapes revealed another pattern. Functional diversity remained relatively uniform across elevations, signalling trait homogenisation often linked to agricultural intensification. Ground-dwelling spiders, particularly from the Lycosidae family, were disproportionately abundant a possible indicator of simplified and heavily managed ecosystems.
Forested areas showed stronger elevational shifts in traits, while human-dominated landscapes supported certain resilient, synanthropic species, especially at lower elevations. But researchers warn that continued land-use change could erode the ecological complexity that underpins resilience in mountain systems already under climatic pressure.
In high-altitude environments, where species pools are naturally limited, the loss of functionally distinct species can have outsized impacts. As agriculture expands and climate stress intensifies, the Himalayas may face not just a loss of species but a weakening of the ecological roles that keep these landscapes balanced.