Solar irradiance and vegetation dynamics at the K/Pg boundary.

In 1980 Luis Alvarez and colleagues published their ground breaking paper which linked the death of the dinosaurs along with numerous other species at the Cretaceous Palaeogene boundary to the impact of a large meteorite on the Earth's surface. The team proposed that the most likely kill mechanism was the development of a global dust cloud that reduced the amount of sun light reaching the Earth's surface causing global cooling and a reduction in photosynthesis. This would have culminated in a reduction in net primary productivity that would have cascaded up the food chain driving extinction. However, despite being published over 35 years ago this elegant hypothesis has never been directly tested.

To test this idea we require techniques that allow us to directly infer this information from the fossil record. The pollen and spore record is one of the most complete temporal and spatial records available to palaeontologists to study. Our proposal sets outs an innovative framework that will use this record to test these ideas. Over the past decade our research programme has demonstrated that the chemical composition of the pollen and spore wall is regulated by the amount of light the parent plant receives. This allows us to use the chemical changes in spores and pollen grains to track sunshine through time. In this application we will use this technique to deliver an understanding of how post impact light environment changed. By collecting high resolution samples across a broad latitudinal range we will be able to constrain the temporal and spatial dynamics of the dust cloud, testing for the first time the major kill mechanism proposed by the Alvarez team.

In parallel will generate new records of K/Pg vegetation as represented in the pollen and spore record to generate broad predictions about how vegetation responded to this iconic global extinction event. We will use this new record to test if the level of extinction is linked to the severity of the Impact winter as measured by changes in spore chemistry. This high resolution record will also then be used to infer changes in vegetation dynamics through the extinction event and determine how this changes with latitude. Specifically we will be able to test if key plant traits such as genome size or pollination strategy (wind of insect pollinated) were associated with extinction and/ or survivorship across the K/Pg in North America.

The study of mass extinctions, particularly the end Cretaceous event which is recognised by the wider public as being synonymous with a meteor impact and the extinction of the dinosaurs, provides an excellent opportunity to engage with the public, particularly in schools. We propose activities targeted at specific audiences for whom this research will have particular resonance and interest.

Engagement with the general public will be delivered via the Yorkshire Fossil Festival, Royal Horticultural Society shows, and local engagement events which include: Science in the Park (annual science festival at Wollaton Hall, Nottingham), Big Bang Fair East Midlands (annual science event aimed at schools, Derby), Nottingham Festival of Science and Curiosity (annual event, venues across Nottingham, and British Geological Survey biennial open day.

Engagement with schools will focus on developing and producing teaching resources. This is a highly effective strategy for engaging with children and young people, and we will develop teaching ideas and resources for use in the classroom, based on this research. Producing resources which: a) target specific topics within the current UK curriculum, b) are developed with input from teachers, and c) are disseminated via sources which teachers already use and trust, will ensure their uptake. A teacher adopting a new classroom resource or teaching idea will often use it year after year, and share it with colleagues, ultimately reaching a much wider group of students than individual visits. This is a strategy that we adopted in our recently completed NERC grant ("500,000 years of solar irradiance, climate and vegetation change" NE/K005294/1).