Photo: The common swift (Veronica chamaedrys) is a westward migrant.
What is the reason behind this research? Have you seen more and more plants coming from the East appearing or do you want to learn about all the styles?
“The title of our post says ‘unexpected.’ We actually wanted to look at how the range of plants was changing due to climate change. We thought plants were moving — northward or higher — to pursue their temperature optimum. But that’s not what we saw in the data. We saw mainly westward shifts, with 39% of all 266 species we examined moving west, 23% east, and northward migration was actually a minority, at only 15%.
“Actually, this isn’t illogical at all, because climate change has only been happening for about the last 30 years, and most of the extremes have been in the last 10 years. Whereas nitrogen pollution has been going on for a much longer period, and has therefore had an impact on how species move For a longer period, but how these environmental changes affect shifts in the range of plant species has not been investigated much because the focus is on these climate hypotheses.
Therefore, this shift between east and west has to do with nitrogen. Is there more nitrogen in the West?
“The climate has a nice north-south pattern, but the nitrogen is very patchy… Belgium and the Netherlands are real hotspots, as is southern England. The Po Valley in Italy is also a red dot on the nitrogen map. Important agricultural areas. So this spatial pattern Much less pronounced, but overall there is greater nitrogen deposition in the west of our study area than in the east and we see species responding to this.
“Generalist species in particular do particularly well in the West due to the large amount of nitrogen, and these are often more generalist plant species with a large distribution area. Westward migrants include the dogrose, the rough smelt, or the common swift. We also see Many common maple seedlings. When food is added, these species can reproduce very well and grow vigorously, meaning they can outcompete more specialized plants in the long run.
“The east-west trends were most pronounced in areas where rainfall had little nitrogen initially, but where nitrogen increased significantly over the years. This is where we see the greatest change in biodiversity.” In the long run, the same plants will appear everywhere, and plants unique to a particular area will come under greater pressure and be outcompeted.. This therefore means that in the future we must protect those areas that remain relatively undisturbed from further nitrogen pollution.
Are you also seeing a shift in the habitat of other species to places with less nitrogen?
“Those more specialized species are much slower, they are very resilient. The trend is also less clear, which is difficult to link to the effect of nitrogen alone. So their habitat is changing too, but less clearly and less quickly, and probably mainly because of the places where they have become locally extinct.” .
How far back in time did you go, and how did you obtain the data?
via a European and North American network, ForestREplot, coordinated by Ghent University. The first vegetation records were made from 1933 onwards and have been digitized in the ForestREplot database. Then those same places were recorded again. All species are described along with their abundance at each site. Our dataset consists of approximately three thousand forest sites, spread across Europe.
How were these analyses?
We first calculated the centroid of each species’ habitat for each record. This is the center of the habitat, corrected for abundance (Incidence of a given species, ed.). These centers of gravity have moved across all species at an average speed of 3.56 km per year, initially westward, but often also eastward. But there is very large variation between species.
“There are many climate change studies that look at how species’ ranges change based on the northern or southern boundaries of their range. But there is often a large margin of uncertainty, because these boundaries are often subject to fluctuations depending on the year, or are distorted by chance observation.” By looking at the focal points of each species’ habitat, you give much less weight to the organisms Outliers. “This makes it a more powerful measure.”
Then did you look at the nitrogen values?
“Yes, there are nitrogen maps available that allow you to calculate the amount of nitrogen precipitation in the past. From this we were able to calculate the average annual nitrogen precipitation for each of the three thousand forest sites in Europe. Each type has a different distribution area across the sites.” 3,000 forest sites, so you can also calculate the average nitrogen precipitation value for each species and then we relate this average value to the displacement of each species’ center of gravity.
Back to the climate connection. Are plants slower to respond or do they simply not respond?
“If we just look at places where specialist plants have gone extinct, we clearly see the impact of climate change: they go extinct locally faster at the southern limit of their habitat, and there it happens faster if the forest is more disturbed.
“So it’s not at all that we don’t see any effects of climate change. Climate change affects how plant species adapt to their environment. The climate effects are less pronounced so far than the effects of nitrogen. In the 1960s and 1970s, there were also peaks in acid rain, That caused nitrogen – but certainly also sulfur pollution, which has a much stronger acidification effect on the environment. In the past, atmospheric pollution has been an important driver of shifts in the habitat of plant species in European forests and we expect nitrogen emissions to decline even further in the future The relative importance of climate change is increasing.
