Livestock grazing is changing soil, plants, and insect populations

In many parts of the world, traditional landscapes once dominated by wild herbivores are undergoing dramatic changes. Livestock grazing has replaced native grazers, leading to shifts in soil composition, plant diversity, and the delicate balance of predator-prey interactions.

These transformations are often subtle, unfolding over years, but their consequences can be far-reaching.

A long-term study in the Spiti valley of the Himalayas sheds light on how this shift is affecting ground-dwelling arthropods, including spiders, ticks, and mites.

The findings reveal a concerning trend – spider populations are dwindling while disease-carrying organisms such as ticks and mites are thriving.

These changes have direct implications for biodiversity, ecological stability, and even human health.

Global livestock grazing – the basics

The expansion of livestock grazing areas has been reshaping landscapes around the world for decades. As global demand for meat and dairy products grows, ranchers and agribusinesses clear more land for cattle, sheep, and other grazing animals.

In places like the Amazon rainforest, vast stretches of trees are cut down to create pastures, contributing to deforestation and habitat loss.

Grasslands, savannas, and even arid regions are also being converted into grazing land, often at the cost of native ecosystems.

Some regions are turning to regenerative grazing techniques, which involve rotating animals across different pastures to mimic natural grazing patterns and allow the land to recover.

Others are exploring plant-based alternatives and lab-grown meat to reduce pressure on the planet.

The challenge is balancing food production with environmental sustainability, and as global appetites grow, finding solutions becomes even more urgent.

While livestock farming plays a major role in feeding the world, its rapid expansion raises a multitude of concerns, many of which we will discuss in this article.

Spiders in livestock-grazed areas

The researchers found that livestock-grazed areas had fewer spiders but more grasshoppers, ticks, and mites. Spiders play a crucial role in maintaining ecological balance by controlling insect populations.

Study co-author Sumanta Bagchi is an associate professor at the Centre for Ecological Sciences (CES), Indian Institute of Science (IISc).

“Spiders are predators; their ecological roles are similar to wolves, lions, and tigers. A low abundance of spiders can release grasshoppers from predator control, and lead to many downstream changes in an ecosystem. Together, these effects alter material and energy flow,” explained Bagchi.

Replacing wild herbivores with livestock

Bagchi and his team have studied livestock’s impact on Spiti valley ecosystems for over 15 years. They note that wild herbivores like yak and ibex once thrived globally but are now confined to protected areas. Elsewhere, domesticated animals dominate.

For the study, the researchers tracked over 25,000 arthropods from 88 taxa, including spiders, ticks, mites, bees, wasps, and grasshoppers.

They monitored fenced plots with either wild or domestic grazers and analyzed soil moisture, pH, and vegetation biomass.

Disrupting arthropod habitats

Shamik Roy, former PhD student at CES and co-first author, pointed out that arthropods have long-established ties with native grazers.

“Vegetation and soil biotic and abiotic variables are intertwined in complex ways that we are still unravelling. Arthropods heavily depend on them for food and home, an association developed over centuries with native grazers in the ecosystem,” noted Roy.

Replacing these grazers disrupts arthropod populations. The study found that spiders declined in livestock-grazed areas, while ticks and mites flourished.

The reasons behind spider declines are unclear, but reduced prey availability and vegetation changes may contribute.

Increasing disease-carrying arthropods

Pronoy Baidya, former PhD student at CES and co-first author, highlights a concerning trend.

“One of the most surprising observations was the massive difference in tick and mite abundance between native grazers and livestock,” Baidya said.

Eighty percent of cattle worldwide carry ticks, which poses risks to both animals and humans. “This is a major concern for zoonotic diseases and One Health,” said Baidya.

Livestock grazing and vegetation

Livestock grazing affects vegetation structure and soil health in complex ways. The study revealed that areas with domestic grazers had different plant compositions compared to those with native herbivores.

Changes in plant types influence arthropod diversity and alter food availability for different species.

Soil conditions, including moisture and pH levels, also shift under livestock grazing. These changes impact microbial communities, further influencing the ecosystem.

Healthy soil supports diverse vegetation, which in turn sustains a balanced arthropod population.

Conservation and land management

To mitigate these effects, the researchers suggest reintroducing native herbivores and monitoring vector-borne diseases. Conservation policies should focus on balancing livestock grazing and preserving ecosystems.

“Currently, most of the commons are rather mismanaged, allowing people from villages to unsustainably utilise these commons for their livelihoods, and in the process denying the local herbivores their grazing areas,” said Baidya.

“Our study will hopefully be an example which may nudge governments to take serious steps for freeing up the commons first and then starting proper ecological restoration of these lands.”

Restoring wild herbivores and managing grazing lands could help rebuild ecosystems and reduce disease risks.

These changes require action to protect biodiversity and maintain ecological balance. Sustainable land-use practices and better management of grazing areas can prevent further ecological disruption.

The study is published in the journal Ecological Applications.

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