FOSSIL ATMOSPHERES: PALEOBOTANICAL RESEARCH AND CLIMATE EDUCATION ON THE ZOONIVERSE

Paleontology increasingly uses large datasets to address broad-scale questions about evolution and ecology on geological timescales. One such question is whether information from fossil organisms can be used as a robust proxy for atmospheric carbon dioxide through time. Here we present the citizen science branch of ‘Fossil Atmospheres’, a scientific experiment designed to refine the Ginkgo paleo-CO₂ barometer based upon stomatal index (percent of epidermal cells that are stomatal pores). The research side of the project is designed to utilize the response of modern Ginkgo biloba trees growing under elevated CO₂ conditions to calibrate the stomatal index record of fossil Ginkgo. A large number of counts of stomata and epidermal cells of a large number of Ginkgosamples are required in order to make this calibration. This was made possible by involving citizen scientists in data collection, through the online platform ‘Zooniverse’, which also provided an opportunity to educate the public on climate research and changing climate in the geological past.

Data collection for this research project proceeded slowly because cell counts are time consuming. Involving citizen scientists greatly increased the rate of data collection, but brought concerns about data quality. A beta testing phase with Zooniverse volunteers provided an opportunity to improve instructions to ensure high-fidelity data, as well as to assess volunteer engagement with the background scientific information we presented on the project page. Analysis of citizen scientists’ estimates shows that modal values of stomatal counts across many volunteers are accurate with respect to counts made by the project’s lead scientist. However, counts of epidermal cells have a wide range, and mean values tend to underestimate expert counts. We demonstrate a variety of approaches to reducing the inaccuracy this causes in the calculated stomatal index, which could be applied for other datasets.

Zooniverse serves as an ideal tool for collection of paleontological data, where the distribution of fossils would be impossible, but where images of many specimens can be made. Such an approach facilitates the collection of a large dataset, as well as providing an opportunity for volunteers to engage with climate research from an unusual, and non-challenging, perspective.