Clare College Cambridge

Dr Andrew Friend

Director of Studies for Geography

What is your subject and specific area of study?

I study environmental science and am based within the Department of Geography. My research interests primarily concern the functioning of terrestrial ecosystems (vegetation and soils) and how they interact with the atmosphere. Understanding environmental controls on vegetation is important because all food and fibre on which humanity depends has its origin in photosynthesis and terrestrial ecosystems play a major role in the dynamics of atmospheric CO2, the most important anthropogenic greenhouse gas. Therefore, there is tremendous interest in forecasting potential impacts of environmental change on terrestrial ecosystems and feedbacks on climate through the global carbon cycle.

The world's vegetation (including marine phytoplankton) and soils have been providing humanity with a little appreciated yet critical service – the sequestering of over 50% of anthropogenic CO2 emissions (mainly resulting from the burning of fossil fuels and deforestation) since the beginning of the industrial revolution. Without this service the concentration of CO2 in the atmosphere would have risen twice as fast as observed, with consequentially greater changes in the Earth's climate than the already 1 °C rise since pre-industrial times. Despite the obvious importance of this net uptake, it has proved difficult to attribute it to particular processes and, perhaps more importantly, predict its future behaviour. We now believe that about half of this net uptake has occurred in the oceans, and therefore the rest of this "sink" must be on land. However there is no consensus as to the process or processes that might be responsible.

Without this knowledge it is not possible to predict future atmospheric CO concentrations, and hence climate, even if we knew future anthropogenic emissions.

Understanding the potential impacts of future climate change and atmospheric CO2 concentrations on terrestrial ecosystems is also important for many other reasons, including the services ecosystems provide humans and their intrinsic value. We would like to know not only responses of processes that will determine the future status of the terrestrial CO2 sink such as photosynthesis, respiration, and growth, but also changes in attributes such as distribution, biodiversity, and resilience. While we have a relatively good understanding of fundamental ecosystem processes for specific sites and species, major challenges remain in scaling this knowledge up in time and space to answer questions of future responses at regional and global scales.

Within my research group we are trying to address these issues by building, testing, and applying mechanistic numerical models of terrestrial ecosystem dynamics that aim to predict the distribution and attributes of global vegetation and soils from the underlying processes. These models can be used "off-line", with inputs from observations of past, and scenarios of future, climate and atmospheric CO2 to predict ecosystem responses, and they can be coupled to global climate/biogeochemistry models to explore feedbacks through changes in land surface-atmosphere water and energy exchange and the global carbon cycle. One striking finding is that uncertainty concerning how terrestrial ecosystem physiology responds to climate change is similar to the uncertainty with respect to future economic growth and technological development for anticipating levels of atmospheric CO2, and hence climate change, to the end of this century! Key processes are the responses of photosynthesis to CO2 and respiration to temperature, as well as the ability of ecosystems to adapt to unfavourable climatic regimes caused by changing rainfall patterns and increasing temperatures. We also use fully coupled models of the global climate system to better understand the major feedbacks that have operated over different periods of Earth’s history, and may be important for our future.

By continuing to develop and test models across a wide range of scales I hope to reduce these uncertainties and produce improved predictions of the properties of future ecosystems and their interaction with atmospheric processes.

What makes Clare College such a good place to study your subject?

Clare College has 2-3 geography students in each year and one fellow, as well as varying numbers of PhD students and post-docs, ensuring a supportive environment for the study of this diverse and exciting subject. The College and Department work closely together to plan supervision teaching and dissertation work, and give general advice on course selection and study skills. Clare is committed to providing a stimulating academic environment with students and fellows working in subjects across the full range of arts and sciences.


Main Publications:

Friend AD, 22 others. 2014. Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2PNAS 111, 3280-3285.

Warszawski L, Friend A, 21 others. 2013. A multi-model analysis of risk of ecosystem shifts under climate change. Environmental Research Letters 8, 044018.

Eriksson A, Betti L, Friend AD, 6 others. 2012. Late Pleistocene climate change and the global expansion of anatomically modern humans. PNAS 109, 16089-16094.  

Zaehle S, Ciais P, Friend AD, Prieur V. 2011. Carbon benefits of anthropogenic reactive nitrogen offset by nitrous oxide emissions. Nature Geoscience 4, 601-605.

Friend AD. 2010. Terrestrial plant production and climate change. J. Exp. Bot. 61, 1293-1309.

Friend AD, White A. 2000. Evaluation and analysis of a dynamic terrestrial ecosystem model under preindustrial conditions at the global scale. GBC 14, 1173-1190.