Ecological theory and experience tell us that plants in meadows and pastures across Denmark should disperse heavier seeds. But they do the exact opposite. If meadows and meadows are allowed to grow wild without human intervention or grazing of animals, nature will slowly begin to change.

For example, weeds do a good job of disturbing cows and sheep as they graze and trample the soil. But weeds are harder to keep undisturbed and then other plants begin to take their place. Competition for sunlight and good soil is increasing. Theoretically, when competition between plants increases, plants that disperse heavy seeds and produce large, thin leaves generally have an advantage. But reality does not follow theory. At least not in Danish nature, and that surprised Christian Frolund Damgaard, the economics professor behind the new findings.

“Heavy seeds provide a competitive advantage in environments where plants compete for resources. The heavy seeds fill a large “lunchbox” and can survive in the shade for some time. Bright seeds, on the contrary, die faster.

Thin leaves will have a competitive advantage because plants can replace old leaves with new ones without expending too much energy. And the new leaves will absorb sunlight better.” But when Christian Freylund Damgaard looks at nature’s data, they tell a different story.

“With increasing competition in these areas, seed size must also increase and leaves must become thinner. But the opposite is happening and I don’t understand why,” he says.

236 natural areas of Denmark examined

Although Christian Frolund Damgaard is a biologist, he works mostly with statistics and large data sets. That’s exactly what he did when he discovered that nature did not behave as the textbooks predicted. After combining 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.

The number of weed species is decreasing. This may be due to less grazing in these areas. But this also means that plants that disperse heavy seeds must increase in size. But they are not. And neither do thin-leaved plants, although this is a natural development.

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

Learn more by sticking a stick in the ground

Most of the data used in the study comes from NOVANA reports. NOVANA is the abbreviation of the Danish name Det Nationale Program for Overvågning af VAndmiljøet og NAturenthe Nation (National Program for Monitoring Aquatic 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 data points collected at more than 35,000 stations across Denmark. Some sites are checked 24 times a year, while others are visited only once every five years.

The data that Christian Frolund Damgaard uses from the reports is coverage data collected using the point detection method. The dot method involves the researcher pushing a stick into vegetation and recording how many times the stick touches different plants. This process is repeated at various points in the field to obtain a representative sample of the plants growing there.

Ecosystems are very difficult to understand

It may seem surprising that the researcher has difficulty explaining what is happening. But this confirms how complex nature really is, explains Christian Frolund Damgaard.

“There are a lot of things we don’t understand about ecosystems. They’re incredibly complex. “Nature seems to change quite slowly, and there may be many reasons for this.”

Kristian Frolund Damgaard does not believe that there is a single explanation for why nature changes and behaves in the exact opposite way as predicted by theory.

“There may be many different reasons. The climate is changing. We are getting more precipitation. The number of ecological niches is increasing. These areas can be grazed less and receive less nitrogen than before. All this helps to change the species composition.

But we may find an explanation for why plants behave this way. “Some manipulation experiments will need to be carried out to test different possible explanations for the behavior of nature,” he concludes.