Predicting damage in disturbed ecosystems

What happens when the balance in an ecological network is disturbed? Anna Eklöf combines mathematics and ecology to predict the consequences for the complete ecosystem when one species becomes extinct in the ecosystem or when the climate changes.

Anna Eklöf in natureAnna Eklöf became interested in ecology at an early age. Photo credit: Anna Nilsen
“We are facing enormous challenges in many ecological systems, and we have to do something. I am driven by the opportunity to get involved in this, and solve a small part of the puzzle,” says Anna Eklöf, senior lecturer in the Division for Theoretical Biology at the Department of Physics, Chemistry and Biology.

Biological diversity is rapidly reduced when animal and plant species cannot continue to exist in their original regions for some reason. Climate change, for example, causes some species to move northwards and become established in regions outside of their original habitat. If the species has a harmful effect on the ecosystem, usually by eating existing species or by competing with them, the new arrival can be seen as an invasive species. The Spanish slug, popularly known in Sweden as the “killer slug”, is one example of a particularly unpopular invasive species. Climate change can affect other species by making it more difficult for them to survive, such that the population falls, or the species becomes extinct in the ecosystem.

“We want to reveal the consequences of disturbing various ecosystems. Our research is based on ecological networks, which describe how species interact with each other, by eating each other or competing for resources. And it doesn’t have to be negative – species can also influence each other in a positive way. Knowledge about how these ecological networks are built and why they have the structure they have enables us to make predictions and understand what will happen when various disturbances occur in an ecosystem.” 

An animal or plant species may be, of course, an unwilling item on the menu for other animals. But species can perform many other functions in the complicated network of an ecosystem, such as pollinating plants, purifying water, or protecting a coastline from storms. The various functions that a species contributes are known as “ecosystem services”. One of the areas that Anna Eklöf and her research group are studying is the ecological network of the Baltic Sea. They are particularly interested in how various threats to the Baltic Sea will influence the ecosystems. She hopes that the research will be useful in practice by making it possible to predict the consequences of a disturbance, before any damage is done.

“What is most obvious in the Baltic Sea is that we are overfishing the large predatory fish, such as cod. This will, of course, lead to them disappearing as a source of food for humans and other animals. It will, however, have further consequences. It is not necessarily the species that interact directly with cod that are influenced most strongly: consequences can arise at other geographical locations in the Baltic Sea or at other places in the ecological network, at both higher and lower levels in the food chains. We want to be able to predict these effects,” says Anna Eklöf.


Mathematics + ecology

Anna Eklöf was drawn to the research area of theoretical ecology by the attraction of being able to make predictions using relatively simple methods. She became interested in ecology around the age of 10, when a brochure entitled “Det naturliga steget” (“The Natural Way”) came through the letterbox at home. It described some climate threats, such as the depletion of the ozone layer (which was a major issue in the 1980s), and included information about ecology.Anna Eklöf at her desk.Anna Eklöf combines mathematics and ecology to unravel how ecological networks are structured. Photo credit: Anna Nilsen

Anna Eklöf’s interest in animals and the environment stood the test of time. After upper secondary school she planned to become a vet, and started to study biology while waiting to be admitted to the veterinary sciences programme. One of the courses dealt with the theory behind ecological models.

“This course really awakened a feeling of ‘This is what I want to do’ in me. I like maths and I like ecology, and here I could get both in one package. I found it exciting to be able to use mathematical models to understand why species influence each other in they way that they do, and to be able to predict what will happen after ten or a hundred years.”
The fishing industry is one example: fishing quotas are calculated from mathematical predictions of how fish stocks will increase or decrease. And similar predictions can be made for many other species than fish, as long as data are available on which to base the calculations.

The advanced simulations that Anna Eklöf’s research group carry out in supercomputers are based on actual data, collected by other researchers. Information about the size of individuals in a species, their habitat, stomach contents and many other parameters are collected into a large database. Scientists conducting research into the Baltic Sea have access to an extremely detailed dataset, with information from around 6,000 species.

The researchers are also looking for general patterns of how the properties of a species are correlated with the ecosystem services they contribute. Is it possible in a freely chosen ecosystem to say that species with certain properties – such as body size, level in the food chain and mobility pattern – have specific functions in the ecological network? In order to approach an answer to this question, the researchers are carrying out analyses in several ecosystems that extend from the Weddell Sea in the Antarctic, over the tropics and up to the Arctic.

 

“Finding correlations that others miss”

Anna Eklöf has deliberately built a research group that has people with expertise within different fields. When she returned to LiU after a postdoc at the University of Chicago to start her own group, she set herself the goal of bringing together people with ecological expertise and people with mathematical expertise and programming skills.Anna Eklöf in nature“It is our duty as researchers to ensure that our results are disseminated,” says Anna Eklöf Photo credit: Anna Nilsen

“The mixture brings a new way of approaching questions. Not only do we have extremely interesting discussions, we also find it easier than ‘pure’ ecologists to adopt techniques from other research fields. The analysis methods and tools that we want to use are often available in other fields, but it’s necessary to master the correct terminology if you want to find them. At the same time, you need extensive knowledge in ecology to be able to pose the relevant questions and see ecological correlations,” says Anna Eklöf.

She finds the most interesting aspect of research to be the opportunity to take up a completely new question, and being able to think completely freely with her colleagues during the initial phases. Finding new pathways is also one of the properties that she believes to be characteristic of successful researchers.

“Innovative thought processes are important for researchers. Furthermore, it is our duty as researchers to ensure that our results are disseminated. We must be able to package the new knowledge in such a manner that it is interesting both for others within the academic world and for society around us. And then, I’m convinced that successful researchers must be able to determine what is interesting. The information is generally freely available around us, but what’s required is to see important correlations that others don’t see.”

Illustration ecological network

Graphic representation of how species (nodes) interact (links) in an ecological network, in this case the Weddell Sea in Antarctica. Killer whale, sea urchins and plankton represent species at different trophic levels in the food chain. Images by: Anna Eklöf. Robert Pittman, NSF/USAP/Steve Clabuesch and Prof. Gordon T. Taylor (via Wikimedia Commons). Images by: Anna Eklöf. Robert Pittman, NSF/USAP/Steve Clabuesch and Prof. Gordon T. Taylor (via Wikimedia Commons).

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