# Drylands Under Pressure: Responses of Insect Density to Land-Use Change in a Tropical Desert

## TL;DR

Insect populations in the Indian Thar Desert decline due to land-use changes like agriculture and grazing, threatening biodiversity and species like the Great Indian Bustard.

## Contribution

Quantifies insect density responses to land-use and grazing in a tropical desert, emphasizing grassland conservation for insect biodiversity.

## Key findings

- Grasslands in the Thar Desert support higher insect densities, especially Orthoptera, during the monsoon season.
- Agricultural expansion and grazing reduce insect populations and disrupt ecological networks.
- Low-intensity grazing and grassland conservation are critical for maintaining insect biodiversity and supporting higher trophic levels.

## Abstract

Responses of insects to land-use transformation and grazing in the Indian Thar Desert were examined across 641 km2 area from 2020 to 2022. Systematic belt-transect surveys showed significant variation in insect densities across habitats and seasons. Grasslands harboured significantly greater densities in monsoon, dominated by Orthoptera, compared to agriculture, barren, or scrub habitats, while livestock grazing further reduced Orthopteran populations. Coleoptera and other taxa displaying weaker habitat affinities. Insect densities exhibited sharp seasonality, surging during monsoon and collapsing in summers. Even low-intensity cultivation and unmanaged grazing were sufficient to diminish insect populations and disrupt trophic networks. Conservation of structurally diverse grasslands, supported by low-intensity grazing regimes, is essential for maintaining insect biodiversity and ensuring prey availability for higher trophic levels, particularly the critically endangered Great Indian Bustard.

Habitat alteration due to agricultural expansion and heavy livestock grazing is a major threat for open natural ecosystems (ONEs). Within the Indian Thar Desert, such land-use transformations are altering native grassland habitats, with consequential effects on insect communities that perform vital ecological functions and support higher trophic levels. Between 2020 and 2022, we surveyed a 641 km2 area, using belt transect and visual detection methods, to quantify insect densities at the order level across different seasons. Linear mixed-effect (LME) models revealed that the orthopteran insect densities, primarily grasshoppers, were significantly higher in grasslands compared to agriculture and barren lands and were lower in the presence of livestock grazing. Orthopteran densities were higher and showed strong seasonal dependencies, likely driven by rainfall-mediated vegetation growth during monsoons. Intense grazing and agricultural expansion reduced vegetation biomass and resource availability, which affected the insect populations negatively. These research findings underscore the urgent need to implement ecologically sensitive land management practices, including sustainable grazing regimes and grassland conservation, to maintain insect biodiversity and the broader ecological network. Given the role of insects in ecosystem functioning and their importance to conservation dependent species of, such as the critically endangered Great Indian Bustard (Ardeotis nigriceps), these findings underscore the ecological significance of preserving native grassland habitats in the Thar Desert landscape.