I use paleoecological methods applied to sediment archives to assess the speed and trajectory of change in ecosystems of the past with timescales from decades to millennia. My research interest is to reconstruct long-term natural changes as background to understand and date environmental impacts of humans through time.

Since 2004, I am Senior Lecturer in Physical Geography at the School of Natural Sciences, Technology and Environmental Studies at Södertörn University. I mainly teach Earth Science in the Environment and Development program.

Selected research projects

Baltic coastal environment the last 2000 years External link.

The aim of the research project UPPBASER External link. is to investigate and date early human impact on Baltic Sea coastal waters the last ca. 2000 years to separate the natural variations in climate from changed land-use causing eutrophication and bottom water hypoxia. In 2020 Lena Norbäck Ivarsson External link. defended her PhD-thesis External link. carried out within this project.

SEASIDE - A multidisciplinary study of maritime environmental history External link.

SEASIDE External link. is a multidisciplinary project with collaboration between maritime archaeologist, marine geologist, paleoecologist and archaeologist. The aim is to disentangle the long-term role of human impact and natural driven processes (e.g. climate change and isostatic uplift). A terrestrial part includes studies of lake sediments for reconstruction of land-use changes (pollen, charcoal), shore displacement (dating of isolated lakes using diatom stratigraphy), archaeological mapping and excavations. A marine part includes mapping of the seafloor with multibeam echo sounding and sub bottom profiling and reconstructions of environmental change using mainly diatom stratigraphy and stable isotopes. Olena Vinogradova External link. perform her PhD-thesis within this project.

The paleoenvironment of the Baltic Sea External link.

I participated as diatom specialist in the International Ocean Discovery Program (IODP) Expedition 347 Baltic Sea Paleoenvironment External link.. My research was conducted within the project Late Pleistocene and Holocene forcing on the Baltic Sea External link. and focuses on the role of long-term climate-driven processes affecting the Baltic ecosystem (changes in temperature, stratification, salinity, primary production and oxygenation) and how these are recorded in the sediment archives. We have further been using the IODP material from site M0063, Landsort Deep, for a pilot study to resurrect resting spores of the diatom genus Chaetoceros from millennia old sediment samples.

Selected papers:

Sanyal, A., Larsson, J., van Wirdum, F., Andrén, T., Moros, M., Lönn, M., Andrén, E. 2022. Not dead yet: Diatom spores can survive in nature for several millennia. American Journal of Botany 109(1), 1-16. https://doi.org/10.1002/ajb2.1780 External link.

Andrén, E., van Wirdum, F., Norbäck Ivarsson, L., Lönn, M, Moros, M., Andrén, T. 2020. Medieval versus recent environmental conditions in the Baltic Proper, what was different a thousand years ago? Palaeogeography, Palaeoclimatology, Palaeoecology 555, 109878. https://doi.org/10.1016/j.palaeo.2020.109878 External link.

Warnock, J., Andrén, E., Juggins, S., Lewis, J.,Ryves,D. B., Andrén, T., Weckström, K. 2019. A high-resolution diatom-based Middle and Late Holocene environmental history of the Little Belt region, Baltic Sea. Boreas 49, 1-16. https://doi.org/10.1111/bor.12419 External link.

Norbäck Ivarsson, L., Andrén, T., Moros, M., Andersen, T.J., Lönn, M., Andrén, E. 2019. Baltic Sea coastal eutrophication in a thousand years perspective. Frontiers in Environmental Science 7:88. https://doi.org/10.3389/fenvs.2019.00088 External link.

van Wirdum, F., Andrén, E., Wienholz, D., Kotthoff, U., Moros, M., Fanget, A.-S., Seidenkrantz, M.-S., Andrén, T. 2019. Middle to Late Holocene Variations in Salinity and Primary Productivity in the Central Baltic Sea: A Multiproxy Study from the Landsort Deep. Frontiers in Marine Science 6:51. https://doi.org/10.3389/fmars.2019.00051 External link.

Andrén, E., Telford, R.J. & Jonsson, P. 2017. Reconstructing the history of eutrophication and quantifying total nitrogen reference conditions in Bothnian Sea coastal waters. Estuarine, Coastal and Shelf Science 198: 320-328. https://doi.org/10.1016/j.ecss.2016.07.015 External link.

Andrén, E., Klimaschewski, A., Self, A.E., St. Amour, N., Andreev, A.A., Bennett, K.D., Conley, D.J.., Edwards, T.W.D., Solovieva, N., Hammarlund, D. 2015. Holocene climate and environmental change in north-eastern Kamchatka (Russian Far East), inferred from a multi-proxy study of lake sediments. Global and Planetary Change 134, 41–54. https://doi.org/10.1016/j.gloplacha.2015.02.013 External link.