Climate change is melting away glaciers around the world, but in the Andes Mountains, a wild relative of the llama is helping local ecosystems adapt to these changes by dropping big piles of dung.
This finding, published Dec 30 in Scientific Reports, revealed that the activity of this animal could accelerate the time plants usually take to establish on new land by over a century, highlighting a surprising way organisms are adapting to climate change.
"It's interesting to see how a social behavior of these animals can transfer nutrients to a new ecosystem that is very nutrient poor," said Cliff Bueno de Mesquita, the paper's co-first author and a research scientist in the Cooperative Institute for Research in Environmental Sciences at CU Boulder. But the current pace of climate change still outpaces the ability of species to find new habitats, he warned.
The changemakers here are the vicuñas. They are one of two wild South American camelids, a group of animals that includes alpaca and llama, which are domesticated species. They live in the high alpine areas of the Andes.
Vicuñas may be less famous than their celebrated llama cousins, but they are no less remarkable, particularly because of where they choose to poop.
Much like how humans use bathrooms, these animals get rid of their solid waste using a designated spot shared by multiple members of a social group. Scientists refers to these communal dung piles as latrines.
Over the past two decades, Steven Schmidt, the paper's senior author and professor in the Department of Ecology and Evolutionary Biology, has studied how microbial life and plants are responding to retreating glaciers in the high-altitude Peruvian Andes.
The deglaciated soils are extremely depleted of nutrients and water—a sea of rocks and gravel that can remain plant-free for over a century.
But during expeditions over the last ten years, Schmidt and his collaborators began noticing patches of plants, all of which seemed to have emerged from vicuña poop piles.
Working with animal ecologist Kelsey Reider at James Madison University, the team trekked to sites in the Peruvian Andes, up to 18,000 feet above sea level, that were previously covered by glaciers. They sampled vicuña latrine soils in these areas and found that, compared to barren soils just a few feet away, soils with vicuña poop contained significantly more moisture and key nutrients, like organic carbon, nitrogen and phosphorus.
For example, latrine soil was made of 62% organic matter. In contrast, deglaciated soil that has been exposed for 85 years at the same location but without latrines contained only 1.5% organic matter.
At high elevations, temperatures tend to fluctuate significantly throughout the day, dropping below freezing every night even during the summer. "It's really hard for things to live, but that organic matter made it so that temperatures and moisture levels didn't fluctuate nearly as much. The latrines created a different microclimate than the surrounding area," Schmidt said.
The team also found high DNA concentrations and a wide diversity of microorganisms in latrine soil samples, suggesting that the latrines provided vital ground for microbes and plants to thrive.
The team said vicuña dung likely accelerated the timeline for plants to colonize a barren, lifeless habitat by a century. These animals deposit nutrients and plant seeds from lower elevations in their poop onto deglaciated ground, and then the seeds germinate, attracting other organisms, including animals that feed on the plants.
Camera footage showed that the patches of plants have attracted all kinds of animals, including rare species never before seen at such high elevations and large carnivores like puma. Vicuñas also eat the vegetation growing in their own latrines.
It could take hundreds of years for the deglaciated area to transition into grassland, which might help mitigate the negative impacts that many species preferring colder climates face as their habitats shrink from climate change, Reider said.
But even with the vicuña's help, the rate of species colonizing new ground is much slower than the rate at which the glaciers are retreating.
Glacier melt across the world has accelerated over the past two decades. Between 2000 and 2019, glaciers other than the Greenland and Antarctic ice sheets lost about 267 billion tons of ice each year. If warming continues, the Earth could lose 68% of its glaciers, a prior study estimated.
In parts of the Andes and other mountain ranges, including the Rocky Mountains, many people depend on mountain snow and glacier runoff for water. It is estimated that shrinking glaciers and snow cover could threaten the water supply for nearly a quarter of the world's population.
"The vicuñas are probably helping some alpine organisms, but we can't assume they'll all be okay, because in Earth's history, we've never seen climate change happen at this speed," Bueno de Mesquita said. "Current anthropogenic climate change is probably the most severe crisis our planet and all living things have faced in the past 65 million years."
