21 December 2015

21 December: Flora in flux

Plant life

Today’s advent calendar researcher researches plants from way out on a small branch of biology called historical ecology. Specifically, she researches how Danish flora has changed over the past couple of hundred years and investigates the causes of these changes. Today is a chance to get to know a bit about Tora Finderup Nielsen, PhD student at the Department of Biology.

Sled dogs
Photo: Carsten Egevang / Qimmeq

While indoor traditions have changed over the past 200 years, so that a silver tip fir tree can now be found in the homes of everyone celebrating Christmas, plants in nature have also experienced change during the past centuries.

If we were to take a walk through the mid 19th century Danish landscape, it would look quite different than it does today. Small plots would be divided by living fences, weeds would be growing between rows of grain and grazing animals would be busy near tall grasses being grown for winter hay. Our socks would also be quite soggy after crossing the many bogs and water holes that once characterised many parts of the Danish countryside.

Enormous changes have occurred in Denmark since the 19th Century. Cities have grown, bogs and fields have been drained, nitrogen use has increased and grazing in forests and green meadows has for the most part ceased. All of this has had an effect on Danish plant life. These transformations are the basis of Tora Finderup Nielsen’s research.

Map of the Northern part of Copenhagen from the end of the 1800sMap from the same area today

Lost natural value

Changes to the Danish countryside have caused many of the plants that were once common in Denmark 200 years ago to become very rare, while a few species have completely disappeared from the list of Danish flora. Among other things, this is due to the draining of fifty-percent of the Danish countryside. The water has been channelled away in ditches and as it has, the countryside has become more and more homogenous. Not all species have suffered. Whether intentionally or not, humans have spread and introduced entirely new plant species to Denmark. The research shows that in many areas, the number of plant species today can exceed the numbers of species found there 200 years ago. In general, the most common and rapidly growing species have expanded at the cost of those that are rare and hardy. Even though Tora Finderup Nielsen says that no single plant is worth more than another, Denmark will lose it’s natural wealth if the flora becomes the same everywhere.

 “If the plants that have disappeared from meadows in Copenhagen were rare both as species and geographically, a rare orchid for example, and if the plants that replaced the orchid are exactly the same as the plants that are already nearby, we don’t just miss something pretty to look at, we lose natural value here in Denmark. Furthermore, if among the flora, characteristic species go missing as do distinctive nature types, the rare insects, birds and other animals will go with them.”

Plant lists as time machines

To find out exactly how flora have changed, Tora Finderup Nielsen uses lists of plants from old botanical guides and excursion notes. By comparing the old plant lists with modern records from similar areas, Tora Finderup Nielsen is able to ensure knowledge of how floras have changed over the past 200 years. These lists also allow her to map how individual plants are being pressed out or else spread, by including information about how widespread draining, grass shortages, fertilizer use, construction or other factors that may have affected the countryside during this period of time.

 “I deduce the changes by comparing old records of where various plant species were once located and where these species are found today, as well as how and why the environment around them changed. We have many ideas about which plants have disappeared or become rare in Denmark, but it really exciting to study this with the help of concrete data from original sources. It is interesting to see if the things that I find accord with our ideas, or if we need to reconsider our appreciation of what controls temporal and spatial plant diversity. I also think that it is exciting to dive into old archives and see who has been researching Danish nature through the ages.”


The aim of Tora Finderup Nielsen’s research is to use historical knowledge about plants to protect the plants of the future. When, by using old botany books, she is able to find an answer for why a given plant became threatened, this knowledge can be used to protect nature in the future.

 “It can be difficult to protect something if we don’t know what it once looked like and what the potential of the countryside is. When we have found out how and why plants became rare or more common in the past, we will also be able to say something about how we should manage our nature areas in the future, so as to take care of what we have left, as well as resurrect some of what was lost.”

Tora sought to continue her research after earning a master’s degree because she thought it was fun, as well as a privilege, to “nerd about” with her things, to constantly learn new things and at the same time disseminate knowledge to both the general public and through the international research environment.