PhD Thesis abstract, final version after revisions, February 2014

Tree cover in the early Holocene in temperate Europe and implications for the practice of re-wilding in nature conservation

This thesis addresses the methodological challenges of determining the variability of large herbivore populations through time and their impact on European vegetation.

Large herbivores are at the heart of conservation policy however, opinions widely diverge on whether we should aim for fewer herbivores and managed populations or, on the contrary (as advocated by the rewilding movement) more herbivores and self-regulating populations acting as ecosystem engineers. This controversy has roots in a debate regarding the nature of ecosystems before the prevalence of human activities. Baseline ecosystems are either described as continuous forest cover with passive large herbivores, or, in contrast, as mosaics with patchy forest cover driven inter alia by bison, aurochs and horses, now rare or extinct in Europe. The main obstacle in moving this debate forward is a poor understanding of large-herbivore densities in the past.

I analysed modern pollen and spore assemblages from known environmental settings to improve palaeoecological interpretation of fossil assemblages dating from the pre-human (baseline) period. The sites investigated are the rewilded grasslands of the Oostvaardersplassen (The Netherlands), the mosaic habitats of The New Forest (UK) and the old-growth closed-canopy forest of Białowieża (Poland).

I demonstrate that the common practice of interpreting pollen percentages fails to estimate past forest cover in situations with natural grazing. As an explanation, I suggest that pollen productivity fluctuates with biotic factors such as herbivory and canopy shading. As a result, new insights into the baseline debate require additional lines of evidence. In this thesis, I develop an existing methodology to reconstruct past herbivore presence using fossil dung fungal spores. I synthesise current knowledge of this method with an emphasis on spore identification and, finally, I demonstrate that dung fungal spore abundance in lake sediments can be translated into large herbivore numbers.

The evidence presented in this thesis contributes to the debate on re-wilding and addresses a fundamental challenge of nature conservation in the human-dominated landscapes of Europe.

December 2013: PhD Viva

December 2013: PhD Viva

Following a challenging, intense and very constructive discussion with the examiners, I passed my PhD Viva with minor corrections, University of Oxford. My examiners were Prof Richard Bradshaw, University of Liverpool and Prof Amy Bogaard, University of Oxford. Many thanks to them and to my supervisors, Prof Kathy Willis and Dr Shonil Bhagwat.

New paper: Do dung fungal spores make a good proxy for past distribution of large herbivores?

Baker, A.G., Bhagwat, S.A., Willis, K.J. (2013) Do dung fungal spores make a good proxy for past distribution of large herbivores? Quaternary Science Reviews 62, 21–31. http:/www.dx.doi.org/10.1016/j.quascirev.2012.11.018

Available online: 27 December 2012

Abstract: The importance of herbivory as a long-term driver of ecosystem change is a topic that has been hotly debated over the past few years. An understanding of the interaction between herbivores and ecosystems is particularly important for conservation policies aimed at re-wilding.

Dung fungal spores have been highlighted as an important potential proxy to reconstruct large herbivore densities across past landscapes. However, this proxy appears to have been used and interpreted in a variety of ways in addition to highly variable taxonomic identification of dung fungal spores.

Here we review studies that have utilised fungal spore assemblages to assess past herbivore presence and test the validity of this method. We aim to determine whether there is a set of identifiable dung fungal spores that can unequivocally track variation of large herbivore activity through time and across regions.

Our meta analysis identifies: (1) spore types that are commonly found to be indicative of large herbivores and their geographical ranges, (2) linkages between these spores and their biological origin, and (3) the most appropriate quantitative method to express their abundance for comparisons through time and across sites.