Glacier Retreat Unveils Truth of ‘Predator First Paradox’

A recent paper published in Molecular Ecology studies ecological evolution in areas exposed by glacial retreat, shedding light on the “predator first paradox,” a phrase used by ecologists to describe the predator-dominated primary succession in glacier forelands. The authors found that predator anthropods such as spiders and beetles can show up as pioneering dwellers on newly exposed land, even before plants colonize the area. The predator first phenomenon shakes up the traditional understanding of a bottom-up ecological pyramid in which plants serve as the basis of the food chain that feeds the predators. Less was known about the prey that sustains these predators in the early stages of succession. By examining the stomachs of insect predators, the researchers determined that spiders and beetles can survive without vegetation on the prey species of local food webs as well as some flying insects.

View from the separating ridge of two of the valleys investigated by the researchers. Gaisbergtal lies to the left and Rotmoostal to the right (Source: Daniela Sint).

Daniela Sint, the paper’s lead author from the University of Innsbruck in Austria, told GlacierHub, “We could show that the amount of local production and the importance to sustain the arthropod predators on those sites was underestimated over many years.” This conclusion is at odds with previous studies that found that flies from other areas, instead of local mites, are the primary food source of the spiders and beetles.

To understand how ecological evolution starts on bare land, the authors selected several glacial forelands in three valleys in the Tyrol region of Austria, namely Gaisbergtal, Rotmoostal and Langtal, which have recently undergone glacial retreat. All three areas have a glacier above them and lie close to each other, with similar climatic conditions. The researchers found that the three glacier toes had retreated 1.5 to 2 kilometers each since 1850, placing these forelands in the early stages of the ecological progress.

Sint and her colleagues pictured as they approach the study sites located close to the edge of the glaciers (Source: Daniela Sint).

Using self-made pitfall traps, the authors collected samples of spiders and beetles from exposed areas to study how the anthropods feed themselves. The paper notes that the authors went so far as to turn over the stones to catch spider and beetle species missed by traps.

“It’s the first time that so many different prey types were molecularly checked for,” Sint explained to GlacierHub. Sint and her team examined the gut of nearly 2,000 spiders and beetles and conducted a DNA analysis on a total of twenty species.

Through the “autopsy” of these captured spiders and beetles, and a DNA detection of prey within their guts, the researchers found only 30 percent of gut content was made up of flies from other places. The rest of the anthropods’ diet comprises mites and other prey found locally.

The researcher’s data shows that the spiders and beetles have dietary preferences toward mites (not flies), regardless of the differences between the sites. Meanwhile, as time passes, the prey options for spiders and beetles increases, providing more food for the predators. Gradually, this positive interaction empowers the substantial development of the food chain and ecological community.

Some dry ground beetles trapped by the pitfall set by the researchers (Source: Daniela Sint).

Although the researchers identified different food sources for the spiders and beetles, resolving important questions about the prey of predators, Sint also discussed with GlacierHub her team’s plans for future research. “We still were not able to cover the whole food web on the study sites. For example, we found out that springtails are very important food for the predators, but we still don’t know what the food for the springtails themselves is,” she said. “There are several options as they might feed on locally produced algae or fungi, but it could also be that ancient carbon and nitrogen released from the melting ice might play a role.” A follow-up study at the University of Innsbruck is currently focused on this question.

Sint says she will continue to research glacier areas, as “glacier retreat is the factor initiating the whole process of primary succession.” When the glacier melts, land that has been covered by ice for thousands of years is “released” and colonization by microorganisms, plants and animals starts immediately.

Sint further described her concerns about global warming-driven glacial retreat worldwide, saying, “This does not only have the local effect of additional land becoming ice-free and being thus available as new habitat exposed to primary succession, but it also has strong influences on numerous other aspects. Many of them will only become obvious once a specific glacier is gone.”

Roundup: The Godfather of Modern Ecology and China

A Hundred Years of Data

From National Geographic: “It’s not often an ecologist gets to play sleuth in so adventurous a fashion— picking through musty papers in the Midwest for 100-year-old hand-drawn maps that lead through dense Alaskan underbrush populated by wolves and brown bears. But that’s how scientist Brian Buma tracked down the work of a legend— a godfather of modern ecology so prominent in his field that the Ecological Society of America has an award named after him.”

Read more about Buma’s trekking and his findings here.

When William Cooper visited in 1916, this bay was filled with glacier ice (Source: Brian Buma).


All Not Quiet on the Western Front

From the BBC: “China has accused India of incursion into its territory between Sikkim and Tibet, in a dispute which has raised tensions between the countries. Officials said Indian border guards had obstructed “normal activities” on the Chinese side, and called on India to immediately withdraw them. India also recently accused Chinese troops of incursion on its side.”

Read more about this geopolitical hotspot here.

The entrance to the Nathu La pass, between India and China (source: Abhishek Kumar/Creative Commons).

On the Tibetan Plateau…

From the Chinese Academy of Sciences: “China on Saturday began its second scientific expedition to the Qinghai-Tibet Plateau to study changes in climate, biodiversity and environment over the past decades. The expedition will last five to 10 years and the first stop will be Serling Tso, a 2,391-square-kilometer lake that was confirmed to have replaced the Buddhist holy lake Namtso as Tibet’s largest in 2014.”

Read more about the Chinese Academy of Sciences’ upcoming research project here.

Satellite image of the Serling Tso lake (source: NASA/Creative Commons).

Roundup: Glacier Lakes, Crevasses and Laws

Each week, we highlight three stories from the forefront of glacier news.

Decreasing Diversity in Glacier Lakes

Glacier lake
Glacier lake (Photo: Flickr)

From Universität Innsbruck:

“Professor Ruben Sommaruga from the Institute of Ecology, and Hannes Peter from the research group Lake and Glacier Ecology have studied shifts in diversity during the transition from turbid glacial to clear mountain lakes and now report on their surprising findings. Their research work has been published in the Nature Publishing Group’s journal ISME Journal.”


Learn more about the research here.

Glacier Crevasses: Observations, Models, and Mass Balance Implications

huge crevesse on the fitzsimmons glacier
huge crevasses on the fitzsimmons glacier (Photo: Flickr)

From AGU publications:

“We review the findings of approximately 60 years of in situ and remote sensing studies of glacier crevasses, as well as the three broad classes of numerical models now employed to simulate crevasse fracture. The relatively new insight that mixed-mode fracture in local stress equilibrium, rather than downstream advection alone, can introduce nontrivial curvature to crevasse geometry may merit the reinterpretation of some key historical observation studies. In the past three decades, there have been tremendous advances in the spatial resolution of satellite imagery, as well as fully automated algorithms capable of tracking crevasse displacements between repeat images.”

Read more about Glacier Crevasses here.

Defending Glaciers in Argentina

Glaciers in Argentina
Glaciers in Argentina

From Taylor & Francis Online:

“Constitutional law has been utilized in many countries to promote the protection of environmental rights, with varying degrees of success. This essay offers gold mining in Argentina as a case study for examination of the tensions that exist between economic interests and the need to protect the environment, notwithstanding the provisions made for environmental rights within the National Constitution. Due to the significance of the country’s glacier region, the Argentine public has resisted mining developments that threaten this natural resource by taking a multipronged approach.”

Read more about Argentina’s law to protect glaciers here.