Facing controversy: Journal Club with Professor Jonathan Leake

In the latest Journal Club blog, Grantham Scholar Emanga Alobwede reflects on the session led by one of her Grantham Supervisors, Professor Jonathan Leake. The paper chosen was highly controversial when it was published in 2009, and so discussing it gave the Grantham Scholars the opportunity to think critically about the challenges that all researchers can face when they come under scrutiny.

This week’s paper

A safe operating space for humanity‘ by J. Rockstrom et al.


When Journal Club was led by Professor Jonathan Leake from the University’s Department of Animal and Plant Sciences, the chosen paper was ‘A safe operating space for humanity’ by Johan Rockström. The paper, published in the journal Nature in 2009, introduced a number of concepts around the consequences of human impacts on the Earth for human wellbeing, and sought to establish a framework for defining limits to environmental changes, beyond which the global consequences for humans are unacceptable. It has been highly cited and hugely influential, but is also very controversial. It came out prior to the Copenhagen Summit on Climate Change and sought to provide a steer to policymakers and politicians in the negotiations.

This is an interesting paper to discuss because it presents appealing ideas that will chime with most people interested in food security, climate change and environmental sustainability. But it is also a paper which, according to its critics, shows the risks of scientists making assumptions that are not fully supported by evidence, or are based more on opinion than established facts and quantitative evidence.

The paper argues that the Holocene (ie, the most recent recognised geological epoch) has been a period of environmental stability that has allowed humans to thrive. However, since the Industrial Revolution, humans have driven the world into a new unstable era called the Anthropocene in which global environmental changes resulting from our activities are having consequences which are likely to damage the provision of safe space for humans to thrive on Earth in the future.

Through the concept of ‘planetary boundaries’, the paper introduces a way of assessing environmental changes, consequent on human actions, which ultimately may threaten human survival. This concept is based on the idea that Earth’s subsystems (such as the Monsoon system) react in a nonlinear way and have certain threshold levels which, if exceeded, would shift these systems into a new, possibly harmful or damaging state, with a negative impact on humans. The paper then identifies nine Earth system processes (which the authors believed were vital in explaining these planetary boundaries) and their respective thresholds. These were climate change; rate of biodiversity loss (terrestrial and marine); interference with the nitrogen and phosphorus cycles; stratospheric ozone depletion; ocean acidification; global freshwater use; change in land use; chemical pollution; and atmospheric aerosol loading.

However, how good is the science underpinning the concepts in the paper?

Our group discussion entailed a fairly detailed critical analysis of the paper with a wide range of issues discussed. We began by attempting to answer the question of whether there is really a “safe operating space for humanity”? It was generally agreed that a safe space is difficult to define – and a ‘safe space’ in one region of the world may not necessarily be the same in another – which is perhaps one reason why this paper is not without its critics.

The paper also mentioned the idea that the Earth system has “tipping points”, and that crossing these tipping points could cause detrimental changes to the earth’s environment. For example, if the earth’s climate warmed up by 2oC, the climate could change suddenly and drastically, resulting in disaster. But some have doubts about this claim too – for many in our discussion, it seemed more likely that tipping points would occur over a wider range of values with their effects seen gradually over a longer time period.

The article also states that we had already crossed the critical thresholds of safety for atmospheric CO2, nitrogen pollution and biodiversity loss – but to us, it seemed there was a challenge in defining these critical thresholds for the nine planetary boundaries. We also questioned the evidence base of author’s claim that biodiversity loss would threaten human development and wellbeing, and felt in general that the paper focused too heavily on biodiversity at the expense of other possibly more important issues such as the soil ecosystem – in particular the loss of topsoil, a critical but often overlooked.

By offering a way of identifying what issues need to be addressed in order for humans to avoid the risk of catastrophic environmental change makes the idea of ‘planetary boundaries’ appealing. The problem with this paper, we felt, was that it did not provide enough supporting evidence on how these boundaries were chosen or even why. There was a general consensus in our discussion that assumptions may have been made in setting these boundaries. Moreover, several of the Scholars argued that the boundaries were more focused on global threshold numbers whereas such issues are better addressed in a regional or local context. For example, reducing nitrogen fertiliser use in some developed countries may be beneficial as it could help in decreasing groundwater pollution, but setting a global nitrogen limit in regions such as Africa would most likely have negative effects as nitrogen is needed in these regions to improve crop yields. This is particularly important, especially in the context of policy and ensuring that policymakers have the full picture when making their decisions. In fact, some of the Scholars questioned how useful this paper would be to policymakers due to their concerns about the author’s approach.

For its critics, a further key component missing from this paper is an objective, quantitative assessment of the risk to humans of environmental change, which the paper claims are “not yet quantified”, though there is data on, for example, air pollution. However, the authors do argue that rates of species extinction are passing the human safety threshold at a higher rate than other processes – though what is perhaps missing here is an example where the extinction of an organism has had adverse effects on human safety. After all, the world might be safer for humans without lions and tigers.

Overall, the paper provoked an interesting discussion about good research practices, and the challenges that researchers can face when their claims are called into question.

Further reading

We must set planetary boundaries wisely‘ by S. Lewis
‘Planetary boundaries are valuable for policy’ by V. Galaz