This fourth topic in the working group of Dr. Susanne Fritz links to the second one, as we study human impacts today as well as from a deep-time perspective. Many species are threatened with extinction today, and the pattern of extinction risk is complex both phylogenetically and geographically. Why are some species and clades more threatened than others? Is it just where they live, so due to spatial variation in anthropogenic threats, or is there something about their biology that makes them more susceptible? Which species traits are commonly associated with high extinction risk from habitat loss, climate change, or overexploitation? Finally, do these trait-extinction risk associations hold across different regions and clades, and can we see the same associations in fossil species that have already gone extinct?
Highlighted publications on human impacts on biodiversity
Tucker, M.A., Böhning-Gaese, K., Fagan, W.F., Fryxell, J.M., Van Moorter, B., Alberts, S.C., … , Fritz, S. A., … & T. Mueller (2018): Moving in the Anthropocene: Global reductions in terrestrial mammalian movements. – Science 359: 466-469.
A multi-author study from the movement ecology group that Susanne contributed to. The study used a unique GPS-tracking database of 803 individual mammals from 57 species and found that in areas with a high human footprint, mammals moved on average only one-half to one-third as much as in areas not impacted by human activity.
Fritz, S. A., Eronen, J. T., Schnitzler, J., Hof, C., Janis, C. M., Mulch, A. Böhning-Gaese, K. & C. H. Graham (2016): Twenty-million-year relationship between mammalian diversity and primary productivity. – Proceedings of the National Academy of Sciences of the United States of America 113: 10908-10913.
Using fossil records of mammals and plants across North America and Europe, we show that higher primary productivity, i.e. net production of plant biomass, was consistently associated with higher mammalian diversity throughout the Neogene, indicating that this relationship is a general ecological pattern in time and space. However, we also show that present-day patterns do not match the fossil diversity-productivity relationship, suggesting that human activity and Pleistocene climate variability have modified a 20-million-year ecological pattern.
Lawes, M. J., Fisher, D. O., Johnson, C. N., Blomberg, S. P., Frank, A. S. K., Fritz, S. A., McCallum, H., VanDerWal, J., Abbott, B. N., Legge, S., Letnic, M., Thomas, C. R., Thurgate, N., Fisher, A., Gordon, I. J. & A. Kutt (2015): Correlates of recent declines of rodents in northern and southern Australia: habitat structure is critical. –PLoS One 10: e0130626. See Fisher et al. below for details.
Fisher, D. O., Johnson, C. N., Lawes, M. J., Fritz, S.A., McCallum, H., Blomberg, S.P., VanDerWal, J., Abbott, B., Frank, A., Legge, S., Letnic, M., Thomas, C.R., Fisher, A., Gordon, I.J. & A. Kutt (2014): The current decline of tropical marsupials in Australia: is history repeating?. – Global Ecology and Biogeography 23: 181-190.
This study and the study by Lawes et al. above were the result of a workshop on ongoing declines of native tropical marsupials and rodents in Australia. Australia has experienced a third of the known historical mammalian extinctions, most of these concentrated in medium-sized species of the arid areas and blamed on introduced red fox. However, since the 1970s dramatic population declines are occurring in small-sized species of the fox-free northern tropics. We found that declining species in the south were medium-sized and in open dry habitats, suggesting continued threat from introduced foxes. In contrast, declining northern species were small and associated with savannah habitats, suggesting an increasing threat from feral cats.
Turvey, S. T. & S. A. Fritz (2011): The ghosts of mammals past: biological and geographical patterns of global mammalian extinction across the Holocene. – Philosophical Transactions of the Royal Society B: Biological Sciences 366: 2564-2576.
This was a collaboration with Dr. Sam Turvey from the IOZ London which investigated over 200 extinct mammalian species together with present-day extinction risk from the IUCN Red List across all living ~5000 species of mammals. We show high spatial and taxonomic selectivity in Holocene extinctions and present-day risk: during the Holocene (i.e. the last 10,000 years), large-bodied mammals have been more extinction-prone nearly everywhere, but today they are primarily threatened in the tropics. This suggests that human activities cause an extinction filter that has already affected big mammals in Europe, North America and Australia and is now striking across the tropics.
Beyond these highlighted publications, Susanne’s PhD with Prof. Andy Purvis at Imperial College London focussed on present-day, global extinction risk in mammals and how this is driven by species’ traits and anthropogenic threats (see her publication list here). Shan has also published on global extinction patterns in mammals (see her publication list here).