Within three years, the soil grew richer and supported more plants
When glaciers melt, they leave behind barren landscapes that can take decades to support plants and animals. But a new study found that within just three years, such exposed land was revitalized by llamas, whose activity nourished the soil and fostered plant growth.
By the foot of Peru’s shrinking Uruashraju glacier, researchers partnered with local farmers to capture and herd llamas on four designated plots. For three days a month from 2019 to 2022, the llamas (Llama glama) grazed the plots, fertilizing them with dung and dispersing viable seeds from droppings and fur.
By the end of that time, the otherwise arid and easily eroded soil stabilized, grew richer in nutrients and supported 57 percent more plant cover than before, geographer Anaїs Zimmer and colleagues report September 24 in Scientific Reports.
Such a revival of the ancestral Andean practice of camelid herding could potentially cushion the crops, animals and livelihoods of local communities from the impacts of climate change, says Zimmer, of the University of Texas at Austin.
As is the case worldwide, glaciers are disappearing in Peru’s Cordillera Blanca mountains at an unprecedented rate. And as the ice shrinks, nearby ecosystems wither: They lose access to summertime supplies of freshwater and sometimes encounter harmful acidic minerals in rocks once covered by the glaciers.
Llamas may help counter some of these effects. Their transformation of the land, as seen in the new study, could reduce rock weathering and help the soil hold onto more moisture, thus limiting the acidic runoff that can poison farmers’ crops. Such contamination is one reason local farmers partnered with the researchers. The animals’ behavior could one day even generate new pasturelands as soil quality improves.
The idea that herbivore grazing may positively impact a landscape is not new. Nor is rewilding, the push to reintroduce key species to their native ecosystems, unique to the Cordillera Blanca mountains. In Finland, for example, the Indigenous Sami are working to reinstall reindeer in deforested taiga land, potentially restoring it. And a group in Spain hopes one day to lift the wild bovine known as the auroch out of extinction, putting it to use in grazing.
But the size and speed of the changes the llamas helped bring about surprised the researchers. From 2021 to 2022, the average amount of plant cover in the llama plots grew from about 9 percent to nearly 14 percent — faster than it did in four control plots. Four new types of plant species also moved into the experimental plots over the course of the study.
The research underscores the valuable roles animals play in shaping landscapes, says ecologist Kelsey Reider of James Madison University in Harrisonburg, Va., who was not involved with the new research. Sprinkling nutrients such as phosphorus over the soil can produce similar effects on plant growth, she says, but “the animals themselves are doing a lot.”
For one, animal poo is special: It holds onto both moisture and microbes. For another, in grazing and trampling on plants, the llamas weed out dominant plants, making space for new species.
For the new study, Zimmer and colleagues primarily chose to work with llamas rather than another native camelid, the vicuña, because llamas are easier to herd and make gentler tramplers. And the farmers that the researchers collaborated with were also particularly invested in restoring llama communities, features of Incan religious rituals. Centuries of Spanish conquest replaced llamas and other wild camelids with foreign livestock that uprooted native plants. Bringing llamas back, the farmers think, might slow or reverse the physical and cultural loss.
Zimmer would like to continue the study for at least a decade to track the full effects of the intervention. While the llamas might help a bevy of plants survive in the region, she says, it remains unclear which will stick around, and whether those will ultimately help or harm the ecosystem.
She also notes that the icy mountaintops also hold religious significance for some communities, meaning that as the ice melts away, some feel as though they are “losing their cultural identities.” By 2100, scientists project that the Cordillera Blanca will lose the last of its glaciers as the Earth warms. If further research with llamas bears positive results, Zimmer hopes local government actors might invest in llama herding as a potential adaptation strategy. It can’t bring back the glaciers. But, she says, it may return a sense of agency to local communities.