Photo of Uno Wennergren

Uno Wennergren

To understand and improve – using mathematics

I have two driving forces in my work. One is to understand why a phenomenon is occurring and the second is a wish to improve a situation or phenomenon. It is probably a motivation in everyone’s life – to understand why someone does something in a certain way or how something is constructed and how to improve a relationship or a construction. I get very excited when the subject revolves around different life forms, the natural world, animals, and people – to understand different phenomena in nature is, for me, a great feeling. But larger still is to see a path to improvement for animals and people alike.

Models and mathematics

Natural phenomena are often very complex with a lot of species depending on each other and depending on environmental factors like climate and pollution. That is why it is often difficult to understand why some species are considered pest species and why others are risking extinction. I use models to try and untangle how a system is set up. This is something we all do when we try to understand something complex, creating a model that is often formulated in our thoughts, but sometimes also described with words. Sometimes we make the model to simplistic and that makes it unable to deal with the complexities of the phenomenon, leading to our solutions not holding up to reality.
To make it more scientific and possible to test these models I use mathematics. I formulate models from ideas that are then made into mathematical equations that I use to search for answers and solutions. I either analyse the mathematical model via mathematical analytical tools – it often shows clear results and solutions without many limitations – or the model is so complex in its mathematics it is not possible to analyse it. To solve that problem, I run simulations and calculations in a computer. I then have a better understanding for the system and possibly find improvements, for example lessen the risk of a species going extinct, keep a pest population down or lessen the risk of a disease outbreak. I have also studied more direct problems such as improving animal welfare using mathematical models to shorten the distance for animal transports, and a project to drastically reduce hunger and starvation on earth by improved recycling of fertilizer and nutrients food system.

Mathematical models

The problems and phenomena that I try to analyse are rather different from each other, but all are connected to the natural world, -plants, -animals and humans. A big question is why are there so many species? What mechanisms enable so many species and life forms to co-habit the same places – why are there not any dominant species that control the habitat? Mathematical models derived from how we perceive the ecological system primarily support the second solution, meaning that a system with a few dominant species is more stable and probable than a system with a large number of species. In my research I have successfully shown a number of characteristics a system can have to improve the likelihood of high biodiversity. We use mathematic analysis the same way as in theoretical physics to study smaller units that create a larger units – this is a way of studying infinitely large systems (for example periodic boundary conditions and KAM theory). This knowledge and methodology makes it easier for us to study how likely it is for a system of species to adapt to changes as a result of climate change and how we change the environment by forestation, farming and urbanization. We do this type of analysis together with researchers who use climate models. A very important tool for us is to use large amounts of data on climate, agriculture and forestry.

Improving existence and wellbeing

Large databases and collaboration also give us an opportunity to study other phenomena and find new possibilities for improvement. In agriculture there are large data sets on livestock, agriculture and transportation. We now know that we can use these big data sets to improve our possibilities to reduce the risk of large outbreaks of diseases, like foot- and mouth disease. We now have developed models that describe how the spread of diseases can occur and what methods that can be effective in combating the spread – models are already implemented in Sweden, USA and Europe. We have also studied how animals are transported today and shown that there are big opportunities to reduce transportation through effective planning. Planning that results in both improved animal wellbeing and a reduction of cost.

Agriculture is the sector of society that eight billion people are completely dependent on. Today, unfortunately, one in eight people still suffer from severe malnutrition due to starvation. This occurs mostly in rural parts of the world where the crops are not sufficient to feed everyone and is a result of using to little fertilizer in the fields. (The self-reinforcing feedback between low soil fertility and chronic poverty. Barrett, C. B., & Bevis, L. E. (2015) Nature Geoscience, 8(12), 907-912). Simultaneously, our water, lakes and oceans are under severe stress, due to eutrophication. The fact that these phenomena occurs simultaneously and is an effect of the same process – how we deal with fertilizer from our stock and societies – is ethically indefensible and unworthy a modern society. In our latest project we combine the data of what crops are grown where, where animals are kept and where people live. From that data we can calculate how to take advantage of fertilizer by transporting it back to the fields. We are doing these type of calculations, not only for countries in EU, like Sweden, but also for Pakistan to make the point that this is a chance to give the billion malnourished people of today a road out of an unacceptable situation. Through that lens, one can also recognize the decrease of eutrophication as a bonus.

Science and society

I primarily publish and present my research in scientific literature. Journals and forums vary a lot as a consequence of the different subjects of the projects, for example Nature, Proceedings of Royal Society, Animal Welfare, Physical Review E, Boundary Value Problems, Theoretical Ecology, 2nd International Conference on Global Food Security and so on. Another very important part of my work and the way the results of my research are put to use is through contact with industry and external organizations. Today I have projects with, among others, HKScan, Skogforsk, LRF, logistic companies, Biogascompanies, Organic farming and so on.


To be able to do my research in this extent and width I, of course, collaborate with others, mainly with the research group in the division for theoretical biology at Linköpings University. It is a group with high aspirations and a lot of competence, consisting of PhDs, postdocs and younger senior researchers. Also, we collaborate with our colleagues at other departments at Linköping University, as mathematics, economics, Tema, and of course other universitys in Sweden and abroad.



Thadei Sagamiko, Vladimir Kozlov, Uno Wennergren (2021) Predator survival analysis of a Prey-Predator system with prey species pool Scientific African, Vol. 14, Article e00982 Continue to DOI
Vladimir Kozlov, Sonja Radosavljevic, Vladimir Tkachev, Uno Wennergren (2021) Global stability of an age-structured population model on several temporally variable patches Journal of Mathematical Biology, Vol. 83, Article 68 Continue to DOI
Jonathan Andersson, Samia Ghersheen, Vladimir Kozlov, Vladimir Tkachev, Uno Wennergren (2021) Effect of density dependence on coinfection dynamics: part 2 Analysis and Mathematical Physics, Vol. 11, Article 169 Continue to DOI
Jonathan Andersson, Samia Ghersheen, Vladimir Kozlov, Vladimir Tkachev, Uno Wennergren (2021) Effect of density dependence on coinfection dynamics Analysis and Mathematical Physics, Vol. 11, Article 166 Continue to DOI
Tim Möhlmann, Matt J. Keeling, Uno Wennergren, Guido Favia, Inge Santman-Berends, Willem Takken, Constantianus J. M. Koenraadt, Samuel P. C. Brand (2021) Biting midge dynamics and bluetongue transmission: a multiscale model linking catch data with climate and disease outbreaks Scientific Reports, Vol. 11, Article 1892 Continue to DOI