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Study: Hot, dry regions see more negative effects from livestock grazing

Melissa Sevigny

A new paper looks at the environmental effects of grazing livestock in arid regions in 25 countries throughout the world. The results show it’s possible to improve ecosystems with grazing—but it’s more likely to cause harm in hot, dry regions like the American Southwest. KNAU’s Melissa Sevigny spoke with soil ecologist Matthew Bowker of Northern Arizona University about the findings.

Tell me what question did you want to answer when you started this research?

The core driving question here is in the drylands of the world does grazing lead to greater ecosystem services? And ecosystem services are those things that ecosystems do that support humans and human society.

Why is that something you wanted to study? I think we normally think of grazing as having a negative impact on the land.

That’s definitely true, it’s widely known there are some costs. But people do it for a reason, because it produces food, for example. What we wanted to do is take a broader look at different grazing intensities at many different settings around the world.

So what did you find out?

Overall, when looking at many ecosystem services together, it suggests that in the warmer and less diverse drylands of the world, grazing tends to have an overall negative effect on provision of ecosystem services to people. But in the opposite condition when you’ve got cooler areas that are more species rich, some of the effects of grazing lean in a more positive direction.

Can you use these results to speculate on what the future looks like? I mean, we know it’s going to get warmer and drier in many areas.

Yeah. That is kind of troubling. The main finding, as I’ll state again, is that in the warmer drylands, grazing impacts tend to be more negative, and most drylands in the world, and most places in the world, are getting warmer right now. I don’t know what the future is, but if you put those two things together, it suggests that grazing impacts are going to become more negative on average.

Are there any implications for managing ecosystems that are being grazed?

One thing we found is that dryland ecosystem that have more plant species—diversity—those tended to be associated with more neutral or positive effects of grazing as opposed to negative leaning. That suggest there’s a role for conservation of biodiversity or restoration of biodiversity whenever possible. Another intriguing finding was the diversity of the mammalian grazers—the most different types of them there were, the less negative impacts were seen… This is something we don’t see a lot in the United States, usually grazing systems in the United States focus on one kind of animal—for example, cows, Navajo Nation there’s a lot of areas with lots of sheep—but you don’t see this intermixing as much. But in parts of the world where that does occur, or can occur, it suggests that you might have some less negative effects, maybe even a few positive effects.

Do you think there’s a role for grazing in dryland ecosystems? There’s a lot of focus on diminishing water resources, and people are concerned about the impact of livestock, but do you think there’s a place for that on the landscape?

My personal opinion is in depends a lot on the culture—on the local culture and society and economy…. There are a lot of regions in thew world where people where people don’t have the luxury of doing an ecosystem services assessment to decide if they should graze or not, this is the way they make their food. But in wealthier developed nations we can have this conservation.

Matt, thank you so much for speaking with me.

All right, thank you.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.