Understanding the biggest collapse of terrestrial vegetation in Earth’s history


The Permian-Triassic Mass Extinction (PTME) was the most catastrophic loss of life in the geological record, driven by an intense burst of global warming (Wignall, 2015). A unique feature of this event, when compared to other ‘hyperthermals’ is a near total collapse of global tropical vegetation (Xu et al., 2022), which may then have led to knock-on effects which amplified global warming and poisoned the oceans (Dal Corso et al., 2020). Tropical vegetation collapse is again a concern under present day global warming (Armstrong Mckay et al., 2022), and the likelihood of this happening can be evaluated through a better understanding of ancient tropical forest collapse.

Figure 1. Permian-Triassic plant collapse timeline. Adapted from Mays et al. (2021).

To better understand the events of the past, and their relevance for the future, this project will build on previous work by the supervisory team – using the latest ‘deep time’ vegetation model (Gurung et al., 2022) to explore what is required for total tropical forest collapse and what the long-term global impacts of this event might have been. By linking the vegetation model to a wider Earth-system model (SCION: Mills et al., 2021) the student will be able to test climate perturbation scenarios for their ability to cause plant extinctions, and will be able to test the impact of Earth’s climate and chemical cycles by comparing model results to geological data. We expect the results to be of great interest to the paleoenvironment and paleoecology community, potentially explaining why some past warming events led to forest collapse and some did not. This information will also be relevant for our understanding of future anthropogenic climate change.

Figure 2. SCION Earth Evolution model. The model consists of a single-box ocean, 2D land surface scheme and steady state 2D atmosphere generated from a 3D atmosphere-ocean general circulation model.

Impact of the research

The question of the regulation of global climate is a top priority in the Earth sciences, and papers on this subject appear regularly in top geoscience journals, as well as leading interdisciplinary publications. The combined field of paleoclimate-biogeochemistry is only just emerging, and many topics remain unaddressed. This project will directly address some of the key questions in the field that are also of interest to the general public, and to climate change policymakers. We therefore expect the impact of this project to be highly significant within the scientific community and beyond. The project supervision team encompasses biogeochemical, paleoenvironmental, plant physiological and paleobotanical expertise from leaders in these fields, who have published in the top journals (Nature, Science, PNAS etc.), as have many of their previous students.


There is scope within this project to develop a wide skill set in vegetation, Earth system and biogeochemical modelling techniques. The researcher will work with key figures in thesae fields and the combined model to be developed here will be very powerful and should lead to many opportunities to expand the work, e.g. for different time periods, or to explore other chemical cycles in more detail. The researcher will also be trained in the scientific method, concise writing and presentation, along with a broad range of additional courses offered by Faculty Graduate School.

Working environment

The research will be based in the Earth Surface Science Institute (ESSI), within the School of Earth and Environment at the University of Leeds, with trips to visit Professor Field in Sheffield and Professor Hilton in Birmingham. ESSI is a medium sized and friendly research institute that includes analytical geochemists, biogeochemists, sedimentologists, palaeontologists and modellers of climate and biogeochemistry. The group holds an annual science day, a BBQ, a pub quiz and weekly informal get-togethers, as well as monthly science meetings for each of the ‘paleo’ and ‘geochemistry’ subdivisions. Project supervisor Mills has received multiple ESSI ‘Star Supervisor’ awards.

Entry requirements

A good degree in one of the natural sciences, mathematics or computing is required, and the candidate should have a strong interest in climate-biosphere-geosphere links and in Earth history. Formal training in numerical techniques is not essential, but some experience in (or at least, enthusiasm for) computing is advisable. All necessary training will be provided as part of the project.

References and further reading

Armstrong McKay, D. I., Staal, A., Abrams, J. F., Winkelmann, R., Sakschewski, B., Loriani, S., Fetzer, I., Cornell, S. E., Rockstrom, J. & Lenton, T. M. Exceeding 1.5 degrees C global warming could trigger multiple climate tipping points. Science 377, eabn7950 (2022).

Dal Corso, J., Mills, B. J. W., Chu, D., Newton, R. J., Mather, T. A., Shu, W., Wu, Y., Tong, J. & Wignall, P. B. Permo-Triassic boundary carbon and mercury cycling linked to terrestrial ecosystem collapse. Nature communications 11, 2962 (2020).

Gurung, K., Field, K. J., Batterman, S. A., Godderis, Y., Donnadieu, Y., Porada, P., Taylor, L. L. & Mills, B. J. W. Climate windows of opportunity for plant expansion during the Phanerozoic. Nature communications 13, 4530 (2022).

Mays, C., McLoughlin, S., Frank, T. D., Fielding, C. R., Slater, S. M. & Vajda, V. Lethal microbial blooms delayed freshwater ecosystem recovery following the end-Permian extinction. Nature communications 12, 5511 (2021).

Mills, B. J. W., Donnadieu, Y. & Goddéris, Y. Spatial continuous integration of Phanerozoic global biogeochemistry and climate. Gondwana Research 100, 73-86  (2021).

Wignall PB. The Worst of Times: How Life on Earth Survived Eighty Million Years of Extinctions. Princeton University Press (2015)

Xu, Z., Hilton, J., Yu, J., Wignall, P. B., Yin, H., Xue, Q., Ran, W., Li, H., Shen, J. & Meng, F. End Permian to Middle Triassic plant species richness and abundance patterns in South China: Coevolution of plants and the environment through the Permian–Triassic transition. Earth-Sci. Rev. 232, 104136 (2022).