Rich is an organic geochemist, biogeochemist and palaeoclimatologist.  From 2013 to 2018, he was Director of the interdisciplinary University of Bristol Cabot Institute which explores how we depend on and shape our planet. From 2018 to 2022, he was Head of the School of Earth Sciences, and he currently holds a joint Professorial appointment between the School of Earth Sciences and the School of Chemistry.

Organic Geochemistry Unit (OGU) website

I obtained a BSc in Geology from Case Western Reserve University (Cleveland, USA) in 1992, and a PhD in Geosciences from Penn State University in 1998.  During my PhD, working with Kate Freeman, I conducted research on how organisms adapt to environmental conditions at the molecular level and how this generates biomarker and isotope signatures that can be preserved in rocks for hundreds of millions of years. In particular, I used recent analytical advances, that allowed the determination of algal lipids’ carbon isotopic compositions, to develop tools for the reconstruction of ancient carbon dioxide concentrations. 

Upon completion of my PhD, I accepted a post-doctoral fellowship with Professor J. S. Sinninghe Damsté at the Netherlands Institute for Sea Research.  This fostered a deeper training in analytical and organic geochemistry, which allowed a diversification of the challenges I would ultimately investigate.  Particularly exciting was using carbon isotopes as tracers of microbial processes, such as the anaerobic oxidation of methane by Archaea and sulphate-reducing bacteria in marine sediments. Although these were fundamentally geological and/or environmental research questions, they illustrated the profound importance of analytical chemistry as a probe into the co-evolution of life and the environment of our planet.

In 2000 I became a Lecturer in Biogeochemistry in the Organic Geochemistry Unit of the School of Chemistry, University of Bristol, and I was promoted to Professor in 2010.  While at Bristol, I have investigated a wide variety of biogeochemical processes in ancient and modern environments, with research topics ranging from the controls on arsenic release in contaminated aquifers to reconstruction of ancient greenhouse climates.  My approach continues to be based on the application of isotopic and organic mass spectrometry to the most challenging and critical questions in these arenas.

This research is inherently interdisciplinary, and I have worked with over 200 Bristol, UK and international collaborators.  In particular, I work with those employing alternative geochemical approaches, microbiologists and earth system modellers.  Such collaborations have created a fruitful environment in which to test ideas, challenge paradigms and generate new hypotheses.  We have developed new biomarker proxies for past marine biotic change, including during mass extinctions; evaluated Earth system sensitivity using new carbon dioxide and temperature records; and examined how methane cycling responds to changes in monsoon systems or rapid global warming.  Some of our key findings include new records for past carbon dioxide that indicate Earth has not experienced concentrations as high as those of today (~400 ppm) for about three million years; observations of pronounced hydrological change during periods of rapid global warming; and evidence for complex biogeochemical feedbacks on global warming via carbon burial, chemical weathering and methane emissions.

From 2013 to 2018, I was Director of the Cabot Institute which engages interdisciplinary approaches to address the major environmental challenges of the 21^st century.  We explore the complex biogeochemical (and wider environmental, ecological and even social) changes occurring in the Earth system but also the new technologies and social relationships required to build resilient infrastructure, low-carbon energy systems, and sustainable food and water security.  Consequently, our research and engagement is broad, exemplified by a focus on understanding, mitigating and living with environmental uncertainty as well as the co-production of new forms of resiliency based on connection, cohesion and creativity. A particular focus of my Directorship was the intersection of environmental and social justice and challenging the lack of inclusion in both the environmental movement and the Earth and environmental research communities.

I completed my tenure as Cabot Director in 2018 and became Head of the School of Earth Sciences; during that time, we have navigated multiple elections, industrial actions, a pandemic and a reckoning with the historical inequities of our discipline - sometimes successfully and sometimes not.

Currently, my focus is on the Organic Geochemistry Unit and supporting recent appointees, pioneering innovations in high temperature GC-IRMS methods, and applying these techniques to the investigation of peatland geomicrobiology.

Summary of key research areas

Proxies for Paleoclimate Reconstruction

Organic matter preserved in ancient marine, lacustrine, and peat deposits are vast repositories of information on Earth’s climate through time. Biomarkers provide insight into the organisms living in the past, and the environmental conditions necessary for such organisms to thrive can then be elucidated. Further information is provided by the isotopic compositions of such biomarkers. Because δ¹³C and δD values of biomass are governed by environmental conditions, compound-specific isotope proxies can be used to reconstruct ancient pCO₂ levels, rainfall, temperature, food web structure, and methane cycling. Our research focuses on the development and refinement of such proxies by using cultures and field samples to identify diagnostic compounds and the controls on their isotopic compositions. We are also engaged in research that applies those techniques to specific problems in Earth history, including mass extinctions, the transition into and out of greenhouse climates, and the evolution of life.

Geomicrobiology
Bacteria and Archaea comprise two of the three Domains of life and are essentially ubiquitous on the Earth’s surface. Recent developments in genetic techniques have reinvigorated the field of geomicrobiology by prompting new discoveries and reaffirming the importance of microbes in biogeochemical processes. At the same time, new analytical chemistry techniques now allow direct contributions to microbiology from molecular biogeochemists, particularly when novel biomarkers are integrated with isotopic determinations. Our work in this area includes studies of the microbiology of CO₂ and methane cycling in peat deposits and the role of archaea in anaerobic methane oxidation. We also study the archaea and bacteria present in extreme environments, such as hydrothermal vents and deep-sea brine lakes. Interest in extreme settings arises from the potential that extremophiles could generate medicinal compounds and the prevailing impression that such settings represent good models for life on the early Earth.

Preservation of Organic Matter
The preservation of organic matter is a topic of much interest to a range of scientists: it is critical to the formation of fossil fuel deposits, has important implications for the global carbon cycle and is an essential process in the preservation of organic materials in the fossil record. Our research focuses on both the types of environmental conditions in the past that would have favoured extensive organic matter burial and preservation (e.g. oceanic anoxic events) as well as the chemical transformation of biological organic matter into kerogen. This latter process is of much interest as it is still unclear from where the aliphatic signature of most sedimentary organic matter derives. However, recent work in our group suggests that organic materials previously thought to be relatively labile, including lipids, could be bound into resistant ‘geomacromolecules’, playing an important role in organic matter preservation and governing its chemical structure.