The frozen pollen report

OCCR researcher Sandra Brügger reconstructs past vegetation changes. As an expert on pollen found in glacier ice, she’s even been featured in The New York Times.

Picture: Manu Friedrich

Just for fun, Sandra Brügger has calculated the number of pollen grains and spores that she’s counted over the course of her dissertation: nearly 1.8 million within four years, a dizzying figure. Imagine looking for a grain of pollen on a microscope slide. Adjusting the microscope. Identifying the grain’s plant species. Hitting a button to count it. Over and over again. 1,800,000 times. Today, the climate scientist can recognize 400 different types of pollen at a glance and says, “Pollen analysis is indeed a special area. Sometimes I kept counting as I fell asleep at night.”

Sandra Brügger never thought that being a researcher — which of course involves more than counting pollen — would be so much fun. “I wasn’t that into science until my master’s thesis,” she confesses in the break room of an old brick building at the Institute of Plant Sciences, just a stone’s throw from the Botanical Garden.

Field research in the Amazon

But while looking for a topic for her master’s thesis she found the perfect project: Fieldwork at the Geographic Institute of Bolivia. This promised an adventure and new horizons. Goal: Using a sediment core from Lago Rogaguado, a large lake in the Amazon region, to figure out the region’s vegetation history. While evaluating data from this natural environmental archive, the student discovered some amazing findings that were even published in a respected journal. Thanks to the corn pollen she found in the sediment layers, she was able to prove that there had been agriculture in the Amazon region 6,500 years ago already — much earlier than previously thought.

This sparked Sandra Brügger’s interest in research. Definitely. All the more so when she encountered new challenges in the research group of paleoecologist Willy Tinner, from whom she had learned about using pollen as a marker of past environmental and climate changes. It was a large project, financed by the Swiss National Science Foundation and called “Paleo fires from high-alpine ice cores”. The interdisciplinary project wanted to use ice cores to reconstruct the history of forest fires in four regions around the world, plus get a picture of the the vegetation dynamics and early agricultural activities in these areas — the part of the project that Sandra Brügger would end up doing her dissertation on.

Now she was working with glacial ice rather than sediments from the bottom of a tropical lake. Ice cores are considered excellent environmental and climate archives, since the ice layers store elements such as charcoal particles, soot and pollen quite well, thus enabling researchers to date them very precisely. Apart from that, “The pollen grains are beautifully preserved in the ice.”


Picture: Manu Friedrich

Mickey Mouse under the microscope

So the doctoral student learned how to process the pollen left floating in melted ice. While she was at it she developed a new, nearly loss-free method and started counting everything from plantain pollen with its nubby structure, to pine pollen with air bags that make it look like the face of Mickey Mouse. At first she regularly had to consult standard works such as the “Amazon Pollen Manual and Atlas” and “Pollen et spores d’Europe”, but over time she hardly needed them to identify the fantastic microfossils under her microscope.

Meanwhile, the 31-year-old has completed her dissertation and analyzed four ice cores — one from the Altai mountain range in Mongolia, one from Illimani in the Bolivian Andes, one from central Greenland, and one from Colle Gnifetti in the Monte Rosa massif in the Alps. And she’s explained in four specialist publications what changes in the composition and type of pollen say about developments in the climate and environment over the course of time.

In retrospect, what were the most exciting findings from these four years of research? “We have a window to the future of the Russian part of the Altai,” says Sandra Brügger, “because we could prove with great accuracy how sensitively the forests in the Mongolian part of these mountains have responded to climate change in the past. And we could show what that means for the future development of the vegetation there.” Over the past 5,500 years, the forests there have always shrunk in times of drought and, to a degree, grown during more humid phases. Today, however, they have disappeared in many places and been replaced by the steppes. A change in the precipitation regime would also threaten the forests on the northern side of the Altai in Siberia. Climate scenarios assume that Central Asia will have drier weather in the future. “Our study has shown that for vegetation dynamics, especially as far as forests are concerned, the availability of water is more important than changes in temperature,” says Sandra Brügger.

Picture: Aurel Schwerzmann

Extreme weather, crop failures and plague

It’s not just through publications that the pollen counter has made an impression within the scientific community. She has also presented her work at conferences and meetings in places as diverse as Krasnoyarsk (Russia), Kyoto and New Orleans. She also spoke at Polar 2018 — an international conference in the Swiss mountain resort of Davos that attracted 2,500 participants involved in Antarctic, Arctic and high alpine mountain research. Sandra Brügger gave a lecture about her analysis of the ice core from the Colle Gnifetti, received an “Early Career Poster Award” and caught the attention of a Canadian science journalist who wrote an article titled “Europe’s Triumphs and Troubles Are Written in Swiss Ice” for the New York Times. In it she describes how Margit Schwikowski, an experienced Swiss ice core specialist and OCCR member, and her young colleague used 1,000-year-old glacial ice and the frozen pollen grains within it to show how Europe was affected by extreme weather, crop failure and the plague in the Middle Ages.

Picture: PSI

The detailed report also quotes well-known American climatologist Ray Bradley, who puts the Swiss study into an international context. Until now, only a few researchers have done detailed investigations of pollen trapped in ice cores, he explains. “Most of the ice cores come from the poles far away from diverse vegetation areas. These studies were quite boring and didn’t show much.” A total contrast to the work of Sandra Brügger and her colleagues in the interdisciplinary “Paleo fires” project.

From catwalk and construction site to climate research

The feature in the New York Times wasn’t a sensation for Sandra Brügger’s family — they’re used to seeing her in the spotlight, but as a successful model, not as a scientist. After grammar school, the young woman from Laupen near Bern spent a year in Milan — in front of the camera and on the catwalk. Later, she financed her studies by modelling, especially during winters in Cape Town. “It wasn’t that much fun,” she says, “and I couldn’t imagine sitting around all day talking about makeup now. It was just a chance to travel and earn money.” So she quit modelling when she began her doctorate.

Between her A-levels and university, the paleoecologist experienced another gap year in addition to her time in Milan. She worked as a bricklayers’ and plumbers’ helper on construction sites. As a teenager she had wanted to show that a woman can do any job.

It seems Sandra Brügger has always had the will, and sometimes a rebellious streak, too. Over lunch in the institute kitchen she shares the story of a dispute over methodology. It annoyed her so much that she was determined to prove why her method of processing pollen trapped in ice was superior to other techniques. As she explained in a scientific publication, the “Brugger Method” significantly reduces the amount of ice required for extracting a a statistically meaningful pollen sample. This is key because ice core samples are hard to come by and highly coveted among researchers. The article, which caused quite a stir, was downloaded so often that the president of the International Glaciological Society, in a personal letter, praised Brügger’s success as a young researcher.

So what’s next in the multi-faceted life of Sandra Brügger? “I could do this forever,” she says during a tour of the office and laboratories where she’s spent the last four years. “This work makes me happy.” Then it’s no wonder that the pollen specialist wants to pursue an academic career. Next target: a postdoctoral stay in the USA.

(April 2019)