"The world inevitably changes. Resilience, the capacity to absorb change, is the key to realize a sustainable world" Interview with Professor Walker, 2018 Blue Planet Prize

May 20, 2022

Resilience has been attracting attention around the world. The importance of this concept is evident in the frequent appearance of the word "resilience" in 169 targets of the Sustainable Development Goals or SDGs set by the United Nations. Professor Brian Walker, a winner of the 2018 Blue Planet Prize, is an ecologist who has long studied resilience. Resilience is the capacity of a system to absorb disturbances and reorganize so as to avoid an irreversible shift to alternative states. We interviewed him about his research achievements and the role that resilience will play in our shift to a sustainable world. (Date of interview: March 22, 2022)

Resilience is nature's innate capacity--learning about where and how to change in this constantly changing world

Prof. Brian Walker
Hon. Research Fellow of the Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Hon. Professor, Australian National University
Prof. Brian Walker

"I have studied resilience for a long time now. It's about learning where and how to change in order not to be changed in this constantly changing world," said Professor Brian Walker, reflecting on his research on resilience. For nearly 50 years he has conducted research in various regions with his fellow scientists and students to clarify the capacity of social-ecological systems, their resilience, to cope with disturbances. As a leading expert in resilience research, he was awarded the Blue Planet Prize in 2018.

In recent years, resilience has become a popular word also in Japan, but what it means differs slightly depending on the fields or contexts in which the word is used. Professor Walker has long been working on resilience in social-ecological systems. In order to learn about resilience, we first need to know about our society.

Professor Walker says human society and the ecosystems in which they are embedded are strongly interlinked. We live in an integrated system of humans and nature, a social-ecological system. It is a very complex system, consisting of many components that operate on different time, space, and social scales. We cannot predict just how the system will respond to disturbances, and the changes are not always continuous.

In this integrated world, resilience is a critical attribute of social-ecological systems. Professor Walker defines resilience as the capacity of a system to absorb shocks and avoid a shift to an alternate state (regime). He believes that the capacity of a system to absorb disturbances and avoid a regime shift* will be a key to achieve sustainability.

Professor Walker says that while it's possible the world could go into a disastrous state, we can use resilience as a clue to explore ways to avoid such a regime shift. But he warned, "Resilience is not about staying the same; it's not about bouncing back to exactly like the system was before. Resilience is all about change--to know where and how to change in order not to be changed in this constantly changing social-ecological system."

*A regime is a set of states that a social-ecological system tends to be in. A social-ecological system can have multiple regimes, and resilience is the capacity to remain in the current regime. When hit by external disturbances like disasters, epidemics, wars, or market fluctuations, a social-ecological system without resilience could easily shift into an unwelcome state: a regime shift.

Thresholds, critical levels beyond which changes become irrevocable: a groundbreaking concept that answers many questions

Cattle in a savanna rangeland, where Professor Walker's resilience research has started
Cattle in a savanna rangeland, where Professor Walker's resilience research has started

In 1974, Professor Walker encountered the concept of resilience while reading a scientific paper written by Professor C.S. Holling, who was also an ecologist. Professor Walker got struck by his concept.

"I still remember, it was late in the evening in my office in the university. I literally smacked my forehead and said, "why didn't I think of that?" Suppose that the amount of something in a system is increasing. If you change the cause of the increase, the system will go back to the original state. But beyond some point, even if you take the cause away, the system will not go back and will change to something different, a different state of that system. It was what I was seeing in real ecosystems. The notion of thresholds, a critical point (where a regime shift occurs) became most interesting to me."

At the time, the basic theory in ecology was ecological succession. It assumes an ecosystem will change its state in a smooth and gradual way. But this theory did not fit the reality he had been observing in savanna rangelands. Professor Walker was wondering why in some rangelands the grass grows back again even after being grazed, but in other rangelands, even after cattle are removed, the rangeland does not go back to its original grassy state and tends to stay in a shrubby state.

He began studying resilience with Professor Holling and participated in research projects on ecosystems in various parts of the world, studying Mediterranean types of ecosystems, forests, lakes and other systems, not just savannas. Through these global projects, Professor Walker became acutely aware that human land use could have significant impacts on nature. He started conducting his research based on the concept that human society and the natural world function as an integrated body. In 1999, resilience researchers established an organization called the Resilience Alliance (RA) to conduct resilience research across disciplines such as ecology, sociology, and economics, and Professor Walker served as its first Chair of the Board for ten years.

"It all started when Professor Holling asked other people working in different systems with similar problems to come together, in what he termed a "Resilience Network". There were maybe six to eight people to start with, including me. It was not an official organization, but was a very informative, stimulating working group, and it grew as more people from different disciplines joined us. We wanted to expand our activity, but had difficulties because we needed funds to continue our research. So we decided to register ourselves as an organization," said Professor Walker, recalling the early days of the Resilience Alliance. He is no longer involved in its operation, but the RA is still active, 20 years after its inception. Under its umbrella, numerous subgroups have sprung up across topics and regions, and many young scholars of the next generation are now involved in its activities.

"I think the RA has played an important role in spreading resilience research and resilience thinking to the world. Social scientists around the world came together for research, brought the resilience thinking back to their institutions, and did their own research there. The best example would be the Stockholm Resilience Centre. It has a very strong database of thresholds," said Professor Walker.

From optimization to diversity and redundancy--resilience challenges our perception of the world

low in nutrients -clear water(top)
above a threshold of nutrients -dense algal blooms (phytoplankton)(bottom)
low in nutrients -clear water(top) above a threshold of nutrients -dense algal blooms (phytoplankton)(bottom)

For about 50 years, Professor Walker has been studying mechanisms of resilience, such as how a resilient social-ecological system is formed. His research provides insights into environmental problems the world is facing, such as climate change and global warming.

"One important idea was thresholds. I, along with other social scientists, did a lot of work focusing on critical levels or amounts of a component beyond which the system will change and start working in a different way and not be able to get back to what it was," said Professor Walker. He cited the case of eutrophication of lakes. When fertilizers flow into a lake from nearby land, productivity of algae becomes higher, turning the lake green like a pea soup. Sometimes small organisms such as zooplankton respond by increasing their numbers, consume algae, and restore the lake to its original state. But once the nutrient influx exceeds a certain level, it cannot return to a clear lake. Resilience, or the capacity to recover, can be understood as a distance to a threshold - how much can the system change before it reaches the threshold. The closer it is, the more it becomes susceptible to slight changes; eventually a small push is all it takes to move from one state to another.

"The first question should always be, 'is there a threshold in the system?' We should then go on to determine the threshold to manage the system."

Another point Professor Walker made was the importance of building resilience in general, in all parts of a system to all kinds of disturbances. Research is identifying attributes such as diversity, and connectivity, that confer resilience in general. He emphasized response diversity, in particular. Response diversity is a key factor in realizing a resilient society. For example, legume species play an important role of fixing nitrogen in the soil. If there are ten different legume species in a land, even when a disaster such as fire or frost hits the ecosystem, at least one or two of them are likely to survive depending on their habitats, cold tolerance, or other factors. In other words, with species diversity, even when a disaster hits, surviving legume species keep functioning to fix nitrogen. But in an ecosystem with only one legume species, the function can be lost because of a particular disturbance, leading the system to a different state.

"One of the problems the world faces now, is that if you have ten different kinds of things all performing the same function, in different ways, people in business (for example) will say, 'That's inefficient. Why do you need ten? Just pick the best one and get rid of the others'" said Professor Walker.

For years, he has been arguing that to create a sustainable world, people should depart from the over-riding goal of optimization and adopt policies and measures that focus on resilience. Human society and natural surroundings are mutually dependent. We cannot separate the two to resolve problems. But humans tend to look at just one of the two, and just a limited part of it, when selecting an optimal approach.

Professor Walker says that policies based on optimization could worsen problems rather than solve them. In reality, such cases abound throughout the world.

He says that humans have been trying to maximize the production of what they want by understanding and managing certain components of a system. But in recent years, people are beginning to realize that this approach seldom works and continuing to optimize is not a sustainable way. Resilience thinking, in which diversity and redundancy are valued, is a new way to perceive the world, replacing the conventional view in which optimization and efficiency are prioritized.

Anyone can practice resilience thinking. Apply its principles to your work and life.

With RA members in Corsica, France. Professor Walker is in the front row third from left. (2007)
With RA members in Corsica, France. Professor Walker is in the front row third from left. (2007)

Professor Walker has retired from research and is now taking on a new challenge. He is currently involved in multiple working groups as an advisor to develop frameworks and methodologies for applying resilience to problem solving.

"We need to ask the right questions. One might ask, 'what is the optimal amount of forest harvesting?' But from a resilience perspective, the question should start with 'is there a threshold to the amount of timber that can be harvested, beyond which the system will change?' The same applies to fisheries. Instead of asking what is the optimum number of fish we can take out of a fishery, we should ask 'is there a particular threshold?' If it seems like there is, or could be, we should then conduct research and analyse the system to establish if there is one, and if so, where it is." said Professor Walker. He is now trying to establish such ways to determine, based on thresholds, what state a system is in and if it is in a transition state or not.

The many threats facing the world - climate change, new pandemics, economic crises, wars and mass refugee migrations, do not act individually. They interact with each other, as one integrated system, with each of them influencing, and usually exacerbating, the effects of the others. We have to establish ways to understand the integrated state the world is in, and make appropriate interventions through resilience thinking.

Professor Walker is one of the Blue Planet Prize laureates who are preparing a joint statement on environmental issues to be published in August, 2022, the 30th anniversary of the establishment of the Prize. What are his hopes and wishes for the future? We asked him to give a message for Japanese people, in particular the youth.

"One thing is clear: the cost of not dealing with environmental issues will be many times greater than the cost of dealing with them. I know young people are very worried about the future, looking for solutions that will work and are doable. Create groups, share ideas, and support each other to deal with issues," said Professor Walker. He assures that resilience thinking is for everyone. He encourages us to learn resilience and apply resilience thinking.


Professor Brian Walker
Hon. Research Fellow of the Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Hon. Professor, Australian National University

He has had a most significant influence on the development of the concept of resilience in social-ecological systems and has highlighted the need to increase it to maintain human society under changing circumstances. His ideas have exerted a significant influence as resilience has been introduced as a fundamental concept and developed in many fields, including environmental conservation, economics, protection, sustainable development and disaster prevention policy. Inspired by his research, studies on sustainability and resilience have expanded tremendously. He was awarded the 2018 Blue Planet Prize.

Mini-biography video of Prof.Walker

An introduction video of Prof. Walker shown at the 2018 Blue Planet Prize Award Ceremony.

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