The struggle to achieve sustainability


This time last year, representatives from 172 governments from around the world travelled to Rio for the Rio Earth Summit 2012.  And thousands of NGO representatives participated in the parallel Global Forum with consultative status.

One year on, we are posting this interview with Professor Georgina Mace, of Imperial College London, made at the time by the Public Library of Science.


Lisa Gross: In this edition of the PLoS Biology podcast, I’m speaking with Georgina Mace, a pioneer in the field of conservation biology and director of the Centre for Population Biology at Imperial College, London.  Twenty years ago, world leaders met in Rio de Janeiro at the first UN Earth Summit and agreed on a plan to reverse poverty and environmental destruction through sustainable development. Yet since then, the human footprint has so transfigured the planet that some scientists say we’ve entered a new epoch, the Age of Man.

This month (June 2012), world leaders will meet in Rio again and try to come up with a new plan at the Rio+20 Conference on Sustainable Development.   The journal PLoS Biology is currently exploring the struggle to achieve sustainability with three articles that revisit a long-standing debate about the limits to growth. Professor Mace provides an overview of the debate and argues that part of the reason we fail to contain our global footprint stems from how we define sustainability.

On one side of the debate, Joseph Burger and colleagues argue that sustainability won’t succeed without incorporating ecological and physical constraints to growth. In response, John Matthews and Frederick Boltz argue human resilience and innovation can save us from ourselves. I spoke with Professor Mace about the sustainability problem last month.

Professor Mace, thanks for joining us. Well, it’s been 20 years since world leaders agreed to tackle the sustainability crisis, but in many ways, we’re worse off than ever. We’ve failed to control greenhouse gas emissions, the income gap is increasing, and most biologists would agree that we’re in the sixth great extinction. So clearly, we failed miserably. But what I want to ask you is why do you think we have? Why do you think we failed so badly?

Prof Georgina MaceProfessor Georgina Mace: I think there are a range of very different reasons. So, some of them are to do with the fact that we really don’t very clearly understand the systems that we’re trying to intervene with. And in many cases, particularly the ones you’ve talked about, the climate in particular but biodiversity loss as well, we do have a pretty good understanding of the natural science going on there. We understand at macro scale what’s driving climate change, what element of human activity is driving climate change. We understand at macro scale why species are being lost.

The problem tends to come down to a much finer level of detail of what kinds of actions at a local or national scale will actually make a difference, how to intervene in that system at a scale at which people live their lives. The solutions are not only in the natural sciences. These are things to do with governance, decision making, politics, policies. So, it’s a complicated set of problems.

Gross: And it’s this notion of placing all these pressures on the environment in a world of finite resources that really lies at the center of the Burger paper. But that’s really an old argument, right? I mean, it started in the 18th century with Thomas Malthus and was revisited more recently with The Population Bomb and Limits to Growth. And these two now classic books inspired quite a bit of controversy more than 40 years ago. Now it seems, with these PLoS Biology papers with Burger and colleagues on one side and Matthews and Boltz on the other, we’re still arguing about the limits to growth.

Mace: You’re right. The Burger paper does start from a traditional Malthusian kind of perspective around the limits to the human population from environmental constraints. I think they take it to a slightly more sophisticated level in laying out exactly how those effects scale from local to global level. And the point they make very clearly is that, within any local system, and they have a very nice example of a very well-managed salmon fishery and the most sustainable city in North America. Those apparently sustainable local systems have impacts elsewhere in the earth’s system. So, they are transporting some of the physical consequences on energy and material flows somewhere else in America or overseas.

So, the observation that, although there appear to be physical limits to growth, they’re not actually confronted very frequently is usually because human activity displaces it somehow. Either it displaces it spatially, or maybe, increasingly, we’re displacing it temporarily with storing up problems for the future. We’re essentially borrowing from future resources in order to maintain the current standard of living.

Now that’s controversial, and it always has been for reasons that have to do with, well, we don’t live in a completely stationary world. We don’t go on using resources in the same way as we did in the past. So, the people who are uncomfortable with the limits to growth as in the Matthews and Boltz paper, gives lots of examples of ways in which those apparent barriers have been overcome by new ways of using resources, by new behaviors, and by the fact that both social systems that use the resources and ecological environmental systems are dynamic. And so, the limits to growth can look like a very static view of the world, that we never progress, we never do things better or more economically or more efficiently and that we always expect everything to be the same in the future as it was in the past.

There are many of these obstacles to growth that can be overcome. But the main point of the Burger article is that there has to be ultimately physical limits, because the earth is a finite system and every living thing and all the living resources on it are ultimately constrained by the resources in that contained system.

Gross: Right. And so, one way people are recognizing these limits is through the idea of green economies. And of course, green economies is going to be a major focus at Rio+20. But as I understand it, there’s not even a consensus about what a green economy would look like, right?

Mace: I think there’s a variety of different meanings to green economies, and it’s not entirely clear to me when you look at the agenda for Rio what is the concept of green economies that’s actually being discussed there. So, Matthews and Boltz actually present a rather sophisticated interpretation of what green economies is, which is economies that are based in the knowledge that sustainable development is dependent on the environment and that people and everything they do has to recognize to fit within natural environmental systems and be limited by them.

Gross: So, to be a truly green economy, it would have to recognize the finite nature of the earth’s resources, find ways to reduce resource consumption, and reduce income equality. But one thing that still comes up in these debates is the assumption that humans aren’t part of the ecology. So I’m wondering if you think this idea that we’re somehow not part of nature may be part of what lets people think unlimited growth is possible.

Mace: Many people, not just economists and so on, but many people believe that ecology is something that happens in wild unconverted landscapes. And that we’ve essentially escaped from constraints in those areas through, you know, building great cities and transport systems and energy plants and so on. And the point that Burger et al. makes is that the fundamental laws of physics and biology apply at multiple scales. And although we’ve learnt and understand more about some of those systems from complex natural unconverted bits of the landscape, it doesn’t mean that those laws don’t operate in areas of high human density nor indeed that they don’t operate when you scale up to whole continents and to the earth as a whole. So, I think ecology’s kind of misunderstood as a science, that it’s quite often viewed as just something that happens in nature where nature is just the unconverted bit of the landscape.

Gross: Then if you accept that we can’t escape from the constraints of physics and biology, then the critical question becomes – and this is what the Burger paper argues – the critical question becomes can the earth support even current levels of human consumption and waste production let alone provide for projected population and economic growth. Do you think that kind of a perspective even has a chance at being heard at Rio+20?

Mace: Well, I think the issues that will be discussed at Rio are very unlikely to get into the level of analysis that’s in these papers. They’re political discussions, and the political discussions tend to revolve around sustainable development as reflected in economic growth and development. So that all the countries at Rio will agree on is the need to reduce absolute poverty, so the billion or so people on the earth who are living in extreme poverty, that is, below a level where their material needs are actually met. And then there’s a lot of people also in the world who live well above that level of their material needs being met. And necessarily, from the kind of arguments that’re in the Burger paper, in a growing population with growing levels of consumption, the only way we’re going to be able to reduce the absolute poverty level is by doing something about consumption at that top level, because we live in a finite world, you can’t go on growing indefinitely in a finite world. So, Matthews and Boltz would say, well, there are many ways of doing this. We can continue to develop and grow but in a more resource sufficient way or we can change our social systems or technologies in order to make that possible.

Unfortunately, I don’t think either of those discussions, either about whether we really do live in a finite world or about how to limit resources used by the developed world in order to make the world’s poorest people to develop. I don’t think either of those will be discussed in any of these more physical settings.

Gross: I wanted to get back to something you raised before, and that’s about the political nature of meetings like Rio+20. So that even if these issues were discussed, the political nature of these meetings raises the prospect that it’s just not even possible to adopt the type of drastic measures needed for change. So, what do you think these global agreements can really accomplish if major world players won’t accept the terms? And here I’m thinking, for instance, the U.S. failed to ratify the Kyoto Protocol on Climate Change. So, what does that say about the prospects of for real change coming from these kind of agreements?

Mace: You’re right. The recent history on these kinds of discussions is not very positive. So, the climate discussions have generally been less successful in recent years than they were a while ago. But I think there are a couple of more positive things about Rio. One is that one of the things that will definitely happen there will be the start of a new process for what are being called sustainable development goals which will take over after the current set of United Nations millennium development goals. So, these are the universally agreed goals to eliminate hunger and poverty, disease and so on, in the developing world.

And the sustainable development goals, these will be more strongly based in the social and natural sciences so that they will be achievable. And they won’t conflict with each other, which has been the problem with some of these goals in the past. So, I think that discussion around the sustainable development goals should be very positive and should be more science-based.

The other thing is, I know I’ve been a bit negative about how the green economy debate will go, but whatever happens in Rio, discussions about green economies inevitably lead people to understand that economic growth is firmly rooted in environmental resources.

Gross: In all of this talk about physical and ecological limits, one thing we haven’t even touched on is where evolution comes in. What do we know about how all this overconsumption, overexploitation of resources, what do we know about how this affects species’ abilities to adapt?

Mace: One of the concerns that Matthews and Boltz has is our view that the world is a static place, that people live their lives in the same way, and that ecosystems are essentially constant in the way they benefit people. And that’s, of course, not true. You only need to look at the history of life on earth to see that major changes to ecosystems have taken place and people and species have adapted to them. So evolution is a process by which fundamental changes take place, genetic material becomes adapted to the new environment. It’s not just a matter of learning to live with it. It’s fundamental changes in the way that organisms operate and interact with each other in a new environment. And evolution and ecology together give us lots of options for the future. It means we don’t have to be constrained by a static world.

The problem with evolution is it takes quite a long time and it can also be quite costly. Strong evolutionary pressures can lead to loss of populations and sometimes to extinctions. But evolution and ecology both feed into this in different ways.

Gross: Well, the fact that species must cope with both ecological and evolutionary constraints does make the prospect of stemming the loss of biodiversity seem even more daunting. I’m wondering what you would tell biologists. What do you think they should do to try to make sure these factors are incorporated into sustainability plans?

Mace: I think what’s needed is a lot more interaction between the sustainable development community who are mostly social and economic scientists and the ecological and biological community, mostly natural scientists. And I think those two together can address some problems that have been very difficult to address otherwise. In particular, the issues that Matthews and Boltz raise about how adaptable are systems. They are optimistic about those adaptability, technological and other kinds of innovation. And we simply don’t know how true that is.

I think we need this new kind of environmental science links to development and the growth of all sorts of ways of the human population. Compared to the benefits of understanding this better, the costs of doing that are really quite small. To quote John Lawton on this, if you think good environmental science is expensive, then try the cost of ignorance.

Gross: And on that note, other papers have been published recently, they weren’t published in PLoS Biology, but other papers recently argued that biodiversity loss is a far bigger problem than even climate change, that it will threaten the well-being of the planet even more than climate change will. So, I have to ask you, are we not taking biodiversity loss serious enough?

Mace: So, a variety of analyses have recently looked at the effect of biodiversity loss on, from a resource availability on the planet, and compared it with the big drivers, such as climate change and so on. And I think that is part of the problem, that biodiversity loss has a much more subtle impact on people than climate does. We’re starting to see the effects of climate change. They’re easier to understand, because they affect things that are very obvious to people, the sea level rise, the frequency of extreme weather events and so on.

But biodiversity loss, we are still at the cusp of the curve where much more loss will be felt. And as that rolls forward, there are many irreversible changes to ecosystems that will certainly affect resource availability. It’s very hard, still, to estimate what the impact of both those kinds of drivers to change will be. Both of them we still have lots of uncertainty about, and that’s partly uncertainly about what the processes are but also how severe the changes will be. And I think those biodiversity loss papers just make the point that we need to take biodiversity loss just as seriously as climate change, because if we don’t do something about it very soon, the consequences for future generations could actually be quite profound.

Gross: That’s it for this episode of the PLoS Biology podcast. I’d like to thank Georgina Mace for sharing her thoughts on the sustainability crisis. If you’d like to read the papers discussed here today, go to Thanks for tuning in.