Nature is behaving strangely and scientists don't know why

Ecological theory and experience tell us that plants in meadows and pastures across Denmark should disperse heavier seeds. But they do exactly the opposite.

Nature begins to change slowly if meadows and pastures are allowed to grow wild without human intervention or animal grazing.

Weeds do well to disturb cows and sheep grazing and trampling the soil, for example. However, weeds have a harder time if there is no disturbance, and then other plants begin to take their place. Competition for sunlight and good soil increases.

In theory, when competition between plants increases, plants that disperse heavy seeds and produce large, thin leaves usually have the advantage. But reality does not follow theory. At least not in the Danish sense of nature – which is puzzling to Christian Frölund Damgaard, a professor in the Department of Environmental Sciences, who is behind the new findings.

“Heavy seeds give a competitive advantage in environments where plants struggle for resources. Heavy seeds are loaded into a large 'lunch box' and can stay in the shade for a while. Light seeds, on the other hand, will die more quickly.”

Thin leaves will have a competitive advantage because plants can replace old leaves with new ones without consuming a large amount of energy. The new leaves will be in a better position to absorb the sun's rays.

However, when Christian Frölund Damgaard looks at data from nature, they tell a different story.

“As competition increases in these areas, the seed size should also increase and the leaves should become thinner. But the opposite is happening – and I simply cannot understand why.”

236 Danish natural areas were studied

Although Christian Frölund Damgaard is a biologist, he mostly works on statistics and large data sets. This is exactly what he did when he discovered that nature did not behave as the textbooks predicted.

After collecting data from 8,859 samples collected from 236 different meadows and pastures in Denmark, he began to see some clear trends: there were fewer weeds, but also fewer plants with large seeds and thin leaves.

Hashish Classify is declining. This may be due to the lack of grazing in the areas. But this also means that plants that disperse heavy seeds must be abundant. But they are not. The same goes for plants with thin leaves, although this must be a natural progression.

“It's a mystery. There's something going on here that we don't understand.”

Learn more by sticking a stick in the ground

The large amount of data used in the study stems from NOVANA reports. NOVANA is an abbreviation of its Danish title Det Nationale Program for Overvågning af VAndmiljøet og NAturenthe Nation (National Program for Monitoring the Water Environment and Nature). Every year the Danish Environmental Protection Agency publishes the NOVANA report on the state of nature in Denmark.

The report is based on more than 250,000 datasets at more than 35,000 stations across Denmark. Some sites are sampled 24 times a year, while other sites are visited only once every five years.

The data used by Christian Frölund Damgaard from the reports is coverage data collected using the exact method. The precise method involves the researcher pushing a stick into vegetation and recording the number of times the stick touches different plants. This is repeated at a number of points within the area to obtain a representative sample of the plants growing there.

Ecosystems are very difficult to understand

It may seem strange that a researcher finds it difficult to explain what is going on. But it underscores how complex nature really is, as Christian Frölund Damgaard explains.

“There are many things we don't understand about ecosystems. They are incredibly complex. Nature seems to change very slowly, and there can be many reasons for that.

Christian Frölund Damgaard does not believe that there is only one explanation for why nature changes and behaves in exactly the opposite way as predicted by theory.

“There can be many different reasons. The climate is changing. We are getting more rainfall. The number of ecological niches is increasing. Areas may see less grazing and receive less nitrogen than before. All of this contributes to changing species composition.”

But we may be able to find an explanation for why plants behave this way. He concludes that it will only take a few manipulated experiments to test different possible explanations for nature's behavior.

References: “The decline of large-seeded species in Danish grasslands over an eight-year period” by Christian Damgaard, 26 December 2023, Vegetarianism.
doi: 10.1016/j.flora.2023.152446

“Choosing against atrocities in the Danish grasslands over eight years” by Christian Damgaard, 13 October 2022, Environmental informatics.
doi: 10.1016/j.ecoinf.2022.101864

“Signal decline in soft-leaved plant cover in Danish grasslands over an eight-year period” by Christian Damgaard, 04 January 2021, Journal of Vegetation Sciences.
doi: 10.1111/jvs.12982