Fieldwork in northern Scandinavia, above the polar circle. What is the first things that come to your mind? Sunstroke? Shorts and t-shirts at midnight? Probably not.

And yet, that was what we got in the first days of this summer’s fieldwork trip to Abisko, Swedish Lapland. Temperatures easily rose all the way to 30 °C, and in the morning, the north of Scandinavia was even warmer than southern Spain.


Temporarily bathroom at our camping site – with a view

While it is rather worrying to see more and more extreme weather events plague the north, I have to admit it did make for rather convenient fieldwork conditions in the mountains. We strategically chose this hottest day on record to camp out on the mountain while surveying plant species composition along mountain trails.


Camping spot in the mountains, with mountain avens (Dryas octopetala) in the front

Two days full of sun, mountain plants and nature, with a steady flow of incoming data, it again made northern Scandinavia in a mountain researcher’s paradise.


Pedicularis hirsuta, just one examples of the beautiful mountain plants we encountered

Now a much-needed thunderstorm broke the heat spell, and brought temperatures back to close-to-normal. Much needed, as the reindeer were seemingly suffering quiet a bit from the heat, searching for every bit of refreshment they could find on the retreating snow beds at high elevations.


A reindeer in search of a cool snow patch, mouth open to cool down

More stories soon of what is turning into an amazing fieldwork stay – as usual.


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Flemish road trip

It might not be everybody’s favorite holiday destination, but we spend last week enjoying a true and original ‘Flemish road trip’.

From Bruges to Brussels, from the port of Antwerp to the outskirts of Kortrijk, we saw it all in a few days time. Our goal? Hunting down non-native plants in their ‘natural’ habitat, with a focus on city environments.


Searching non-native Asteraceae in the port of Antwerp

The peculiarities of this goal made for some interesting sightseeing opportunities, as it turns out that most of our study objects (a set of 8 non-native Asteraceae species) seem to have a preference for what one could call ‘ugly places’: cracks in pavements, depressing flower beds, busy crossroads, abandoned roadsides… Flanders seems full of them, and non-native species are thriving there.


This pavement was not going to win any beauty contest, yet it did host at least 3 interesting non-native species

The occasional relief was provided by Telekia speciosa, a species that mostly seems to escape from large, rural gardens, with a love for the shadow-light dance of the forest understory.


Telekia speciosa with a brimstone butterfly

Beautiful or not, our treasure hunt through Flanders cities has been highly successful so far. And that could have been different. We relied for a large part on freely-accessible observations of our species from the previous decade, and it was always a mix of excitement and fear when arriving at a new locality: would the mentioned species actually be growing there at the moment? Many a population had been destroyed, wrongly named or simply wrongly georeferenced, which did not facilitate our search.


Measuring Matricaria discoidea along a Flemish road

Yet in the end, the harder it was, the bigger the reward when seeing those beautiful flowers looming in the distance when turning the last corner after a long drive. Scientific treasure hunts as they should be!

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Running off the road

It is a known pattern by now, as it is confirmed over and over in virtually all mountain regions we study: roads are facilitating non-native plant species introduction into mountains. Humans introduce – on purpose or by accident – new species in the valleys and from there, they start spreading uphill. On their way up to high elevations, mountain roads serve as a great highway. Yet with increasing elevation, less and less non-natives will be found, as they progressively drop out the higher you get. The few that make it all the way to the top by road, could possibly spread from there into the natural mountain vegetation, but even less species manage that.


Mountain roads – and the cars and people on them – facilitate non-native species movement up to high elevations. Here: Davos, Switzerland

All of that we knew, indeed, yet a crucial question remains: who wins this race to the top? What traits make a non-native species good at this quest for the high elevations?

These questions we aimed to answer in our latest paper in the journal Biological Invasions, using our multiregional MIREN database ( We looked at all these species that are travelling uphill, and hunted down the global patterns.


You’re eager now to know what turns these non-native plants into winner material, right? Well, the key is: it’s a lot tougher than you might think. The magical words describing the problem these plants face: the double filter.

First of all, the colonizing non-native species need to be able to handle roadside conditions: highly disturbed environments, with open vegetation and a peculiar microclimate. Moreover, they should be able to handle these conditions along the whole elevational gradient, from warm all the way to cold conditions. That is the first filter, which slashes out a lot of species. Annual species are progressively filtered out like this, for example, as it gets increasingly hard to perform your life cycle within one growing season. Warm-adapted species slowly disappear as well (yet not as fast as we assumed).


Some non-native plant species are better at reaching the top of a mountain road than others. Especially those that are good at handling the open, disturbed conditions of mountain roadsides and the cold of high elevations. Here: happy tourist on a mountain top in Yellowstone National Park, USA. 

Then there is a second filter, one that decides if you can run off the road, into the natural vegetation. This filter selects for totally different traits than the first one: moist- and shade-adapted species do better in this case, for example, as they’ll need to colonize an environment that’s already covered with plants.


Colonizing the native mountain vegetation is easier if you can handle the shade underneath their leaves. Here: meadow vegetation in Dischma, Switzerland.

It is unlikely that many species have traits that help them pass both those filters at the same time. And then we haven’t mentioned the specificities of the receiving habitat yet: conditions there should also promote non-native species colonization, for example through the availability of bare ground. These results thus show that a lot of things need to be ‘just right’ for a non-native species to succeed in high elevation natural environments, which explains why so few non-native species are currently present there: passing the double filter test is just really hard.


Achillea millefolium (common yarrow, here in Montana, USA) seems to be a species with the potential to pass the double filter, as it is successful in mountain regions worldwide. Further studies will have to figure out what exactly makes it stand out. 

So we do not have to worry about non-native species invasions in mountains? Well, not quiet. There is another common pathway of introduction that helps non-native species to get around this double filter issue. Indeed, if humans introduce mountain plants directly at high elevations, for example in ski resort gardens, invasion becomes much more likely.


Want to know more?

McDougall, K. L., Lembrechts, J., Rew, L. J., Haider, S., Cavieres, L. A., Kueffer, C., … & Seipel, T. Running off the road: roadside non-native plants invading mountain vegetation. Biological Invasions, 1-13. Check it here or contact me for the full paper

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The future is starting now! Today, I got the news that my application for a 3 years postdoc from the Research Foundation Flanders (FWO) has been granted.


Preparing for a future filled with mountains

That means that from October onwards, I can spend my time diving deeper into the effects of microclimate and disturbances on species distributions in mountains, with the help of the greatest network of scientists I know (MIREN).


3 years to study – among others – the interesting and drastic effects of human disturbances (like here in roadsides) on mountain vegetation

I am truly grateful for this opportunity to hunt for the answers on all these questions that popped up throughout my PhD, and tackle all the challenges I found on our way to accurately predict where plants grow, and where they will go to in the future.


This postdoc should expand my current focus from the northern Scandes in Scandinavia, and bring me among others to the beating heart of the European mainlands: the Alps. (Here: Davos, Switzerland).

So please stay tuned! This blog is going to be around for a while, as I’m thrilled to share all these amazing scientific discoveries with you.


I will also use this opportunity to truly include mountain trails in my focus, and compare patterns along them with what we know from mountain roads

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Trail adventures

Interested to join our MIREN Trail Survey? Find all the details here. The story below gives you a feel of how it works.

The 20th of June, Davos, Swiss Alps. The day before the longest day of the year, and amazing weather is predicted. Also the day on which I decided to kill several birds with one stone.

I had to be in Davos for the Polar2018-conference, which brought together scientists studying the Arctic, Antarctic and high mountains. And this visit to Davos provided the perfect opportunity to collect data for our MIREN Trail Survey (all details on it here). With this global survey, we study some globally distributed plant species along mountain trails; and everybody can help. This summer, we are launching the project in full, with athe help of a great app – Survey123 – that makes joining very easy. By now, we already collected up to 3000 data points, and have engaged scientists in 13 different countries; and summer only just started!

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A hiking trail in the Swiss Alps with Alpine’s bird foot’s trifoil (Lotus alpinus)

So I added a nice Swiss trail to the growing list of sites. A local mountain trail ecologist suggested me the ideal one: hiking up in the Flüelapass from Tschuggen to the top of the Pischahorn. A nice hike with some ideal features for the survey: it started above treeline, which increased the chance that I would pass the upper limit of our study species’ distribution rather quickly. It also crossed 1000 meters in elevation, which promised a nice climate gradient, and it was rather touristic. The latter fact is interesting, as we are focussing on species that are following humans up in the mountains. This trail would allow us to check if they do that in Switzerland as well.

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Red clover – one of our study species – in grassy trailside vegetation in the Swiss alps

I decided to focus on all 4 of our study species: white clover (Trifolium repens), red clover (Trifolium pratense), common yarrow (Achillea millefolium) and narrowleaf plantain (Plantago lanceolata). A brave plan, as searching all of them would slow me down a bit, especially in their native range, where they can be common. The Survey123-app allows you to mark the first and last occurrence when a species occurs continuously, but even then you have to keep a close eye on the trailside to make sure the species is still there. If you are new to the project, or have limited time, I thus recommend focussing on one species only. In that case, it’s even easier, as you can save your answers as favourites in the app, and copy-paste them for each observation.

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White clover along my study trail

As predicted, the first meters of the survey went rather slow. The two clover species and common yarrow were very common in the grassy trailside vegetation, and I had to walk slowly to find them all. Especially common yarrow turns out rather hard to find this early in the summer, before the flowering period. Luckily, the plantain was nowhere to be found; one species less to keep an eye out for!

Soon, however, things started to change. The vegetation became more alpine, and the grassy patches slowly dissappeared at around 2000 meter. With them, our three species vanished. That was no reason to stop hiking, though. The higher elevations might hold some surprises, and the absence of occurrences is highly valuable as well. We are planning to use these detailed observations to model the distribution of the species along mountain trails with high accuracy, and knowing the ‘true absences’, i.e. where the plants do not occur, is in that regard very important. So I kept hiking up, and enjoyed the fact that it just went a lot faster!

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At high elevations, the alpine vegetation gets sparser, and our study species disappear

And indeed, the high elevations did hold a surprise: at around 2500 meter, so 500 meter higher than their last occurrence, the species suddenly reappeared! The reason: a ski lift and a restaurant. Such introductory points are crucial for the distribution of our species, so the app allows you to mark their location as well.

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The ski lift, a quick way to the top for seeds of our study species

After that, it was over. Vegetation cover decreased rapidly, and only rocks remained. No chance for our species. Yet again, hiking up provides us the ‘truly observed zeros’ that are so crucial, so I added another 400 meters to the top. A relaxed climb that felt like a holiday, as did the beautiful views on the leisurely way back.

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The trail at the top of the Pischahorn

So after less than 6 hours of hiking, I made it back to the car, having realised a hike of over 10 kilometers that delivered me tons of beautiful views, a bunch of unforgetable memories and 300 interesting datapoints. Who knows a better way to spend his time?

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Trailside vegetation with alpine daisy flower, and the ski lift in the background

Interested, and tempted to try as well? You should! We welcome data from any mountain anywhere in the world. Just one more hint: I noticed the gps of my phone needs some time to become accurate after it fell asleep. This is important to keep an eye on, as the power of our approach lies in the high accuracy of the observations. We need an accuracy of around 5 meters, as we will use the data as presence/absence in pieces of trail of 5 meter.

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The chapel of Tschuggen in the early morning: the start of my hike

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The Alps

How can one be a mountain ecologist without ever visiting the European Alps?

Making up for this now with a visit to Davos, Switzerland, with a visit to Polar 2018, where I will be presenting our work on the ‘third pole’, i.e. the mountains.

More stories and pictures soon, when I hunt down better internet.

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Hunting down plants

I introduced him already in an earlier post: our hero of this spring is the easy-to-overlook flower called Matricaria discoidea, the pineappleweed.


Pineappleweed along a trail in Zemst, Belgium

We are hunting down populations from all over Belgium to explore differences caused by humans: are the plants growing differently in an urban environment than in a rural one? What about a park in the city, or a little village in a field of green? We know a lot about how animals react to the city: bigger butterflies, smaller spiders, birds singing higher, lizards with longer legs… We hope that our little friend will be generous in providing answers on such questions for the plant world as well.


Zemst in early summer, an oase of greenness in a sea of concrete

This time I went to the greenness of Zemst, between Antwerp and Brussels. There, we can still find some nice rural areas amidst all the concrete of the heavily populated center of Flanders.

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