March 10, 2020

expert reaction to research on collapse of large ecosystems

Research, published in Nature Communications, reports that large ecosystems, such as the Amazon rainforest, could collapse and disappear quickly once a crucial tipping point is reached.

Professor Alexandre Antonelli, Director of Science at the Royal Botanic Gardens, Kew comments:

“The authors used 12 modelling exercises to arrive at their conclusions, which is a sensible thing to do as every model makes its own set of assumptions. They then compared their results with 42 known cases of regime shifts. These are relatively few – only four terrestrial shifts were included, of which a single one (the Sahel) went from a forested landscape into desert and could be somewhat comparable to the Amazon – but all reality checks largely support the study’s predictions.

“The implications of this study for the Amazon are terrifying. If the models are correct, current deforestation could lead the whole ecosystem to pass a point of no return as soon as next year, and shift the entire rainforest into a huge savanna or desert in less than 50 years. Unless urgent action is taken now, we may be on the brink of losing the world’s largest and most biodiverse rainforest, which has evolved for at least 58 million years and sustains the lives of tens of millions of people.”

“Nature is fragile. Just because an area is big or a species is common, it doesn’t mean they’ll last forever. The Sahel – an area south of the Sahara that is six times the size of Spain – went from being vegetated and bountiful to just a desert in a few hundred years. The American chestnut – one of the most important trees of eastern North America – almost faced extinction after a fungal disease caused some three to four billion trees to die in the early 1900s.”

“Natural ecosystems are usually resilient to change when kept intact, but after decades of disruption, exploitation and climatic stress, it should come as no surprise that they are breaking down. In other words, you can’t simply remove huge chunks of a rainforest and hope everything will be fine – it won’t.”

“Based on these results, 2020 is our very last opportunity to stop Amazonian deforestation. The United Nations should declare Amazonian deforestation a global ecocide, and work with the South American sovereignties to ensure proper compensation and recognition for preserving the Amazon – for the benefit of people and our planet.”

Prof Georgina Mace, Professor of Biodiversity and Ecosystems at University College London, said:

“There is much discussion about tipping points in the Earth’s major ecosystems; these lead to regime shifts or relatively rapid changes in structure and function. They are of particular importance in ecosystems that play a role in regulating critical earth systems (such as the climate), or that underpin substantial natural resources and local livelihoods, such as coral reefs. While previous studies have modelled individual ecosystems, and there is a large body of general theory about tipping points, this paper is the first to build on a wider evidence base that uses observations as well as theory and modelling. It has quite general implications.

“The main, rather alarming, finding is that large ecosystems, such as those at the scale of the Amazon rainforest, may shift in structure and function quite rapidly, even over a period of decades. While large ecosystems are generally found to ‘tip’ over longer periods, the shift is relatively rapid in larger, more mature systems for reasons that become apparent from network modelling and seem to be borne out by observations. Unfortunately, it is also clear that a history of relative stability in these large systems is not an indicator of their future stability or resilience. Once damaging pressures start to have effect they propagate rapidly through these large ecosystems.

“I think the combination of theory, modelling and observations is especially persuasive in this paper, and should alert us to risks from human activities that perturb the large and apparently stable ecosystems upon which we depend. The findings of this paper come in the same week as a study using field data documenting the declining carbon store in tropical rainforests, most markedly the Amazon¹. This is a further reminder that this ecosystem, providing a globally significant carbon store, as well as being a hotspot for global biodiversity and supporting the livelihoods of millions of people, is at risk over a time scale of no more than a few decades. There are effective actions that we can take now, such as protecting the existing forest, managing it to maintain diversity, and reducing the direct pressures from logging, burning, clearance and climate change.”

¹ Hubau, W. et al. Nature 579, 80–87 (2020)

Dr Erika Berenguer, Senior Research Associate at University of Oxford and Lancaster University, said:

“Although the publication presents an interesting intellectual and computational exercise, its conclusions are not supported by the data analysed. The authors use data from only four terrestrial systems, none of which is a tropical rainforest, but still claim that the Amazon, the largest rainforest on the planet, will experience a dieback in just 50 years. In the press release the authors claim that the Amazon will become a ‘savannah-type ecosystem with a mix of trees and grass’ when that simply wasn’t tested in the paper.

“It is very unlikely, if not dystopian, to expect that an area half the size of Europe will experience a complete shift in vegetation in just 50 years. This would require dispersion rates of savannah trees and grasses at a speed never seen before. While there is no doubt that the Amazon is at great risk and that a tipping point is likely, such inflated claims do not help either science or policy making.”

Prof James Crabbe, Professor of Biochemistry, University of Bedfordshire, said:

“This is a thorough and well researched paper, bringing together observations with five computational models which show that even large ecosystems could collapse within decades after abrupt changes in their composition.  The authors point out clearly the potential ranges in their modelling, so those decades could be lengthened to centuries if humans react quickly.

“This work should motivate us to enhance conservation efforts and management of local and global threats, to improve the long-term prospects of rainforests and coral reefs. Success in such conservation ultimately depends on governments and scientists meeting the science-based targets agreed in the 2015 Paris agreement.”

Some additional comments from international researchers, supplied by the British Ecological Society:

Professor Tom Crowther, Climate Change Ecologist, ETH Zürich, Switzerland:

“The rapid shifts from one ecosystem state to another can have considerable impacts on biodiversity and can drive ecological feedbacks that can alter the climate system. This research highlights how rapidly these shifts can take place, even for large ecosystems. Understanding the rate of these regime shifts will be valuable as we aim to forecast changes in biodiversity and climate change into the future.”

Dr Ruben Helano, Ecologist, University of Coimbra, Portugal:

“This study provides compelling evidence that entire ecosystems can collapse within a few years to decades and highlights structural attributes that can help us to predict such collapse. This works represents an important call for considering entire community structure and integrity when planning conservation efforts.”

Ima Vieira, Ecologist Museu Emilio Goeldi at Belém, Pará, Brazil:

“This is a very important paper. For Brazil to avoid the ecosystem collapse modelled in this study, we need to strengthen governance associated to imposing heavy fines on companies with dirty supply chains, divestment strategies targeting key violators and enforcement of existing laws related to environmental crimes. And we have to be quick! Brazil previously had a positive record having reduced deforestation by 80% from 2005 to 2012 but now it is scaling up again and the consequences of it are terrifying.”

‘Regime shifts occur disproportionately faster in larger ecosystems’ by Gregory S. Cooper et al. was published in Nature Communications at 4pm UK time on Tuesday 10 March.

DOI: 10.1038/s41467-020-15029-x

Declared interests

Dr Berenguer: no conflict of interest to declare.

No others received.