A group of scientists has warned – in advance of the Earth Summit 2012 that opens in Rio de Janiero tomorrow – that biodiversity loss could accelerate and produce a “global-scale state shift” in which large numbers of species become extinct.
The prospect that biodiversity loss could move sharply and dangerously, in a manner analogous to the tipping points in global warming that climate scientists warn of, is raised by University of California biologist Anthony Barnosky and 21 other colleagues in a special issue of the journal Nature (list of contents here).
Newspaper coverage of Barnosky and co’s article perhaps inevitably focused on possible catastrophe (e.g. this interview) – although the actual text emphasises scientists’ uncertainty about the impact of the rapid biodiversity loss. A second article, by Bradley Cardinale of the University of Michigan and 16 others, surveys the progress made by biodiversity research in the 20 years since the original Rio summit – and it, too, acknowledges the great uncertainties that remain.
It’s a macabre irony of 21st century capitalism that, while these articles discuss potentially devastating threats to human life and society, if you don’t have university library membership or £22 to spare … you can’t read them. Perhaps hackers will liberate them from their pay walls, and if they do I’ll be pleased to put the word around. In the meantime, here are some key points:
Barnosky and his colleagues argue that “planetary-scale critical transitions have occurred previously in the biosphere, albeit rarely” – and “humans are now forcing another such transition, with the potential to transform Earth rapidly and irreversibly into a state unknown in human experience”.
Their list of previous “critical transitions and state shifts” includes the “big five” extinctions, one of which was 65 million years ago, and the others more than 200 million years ago. But the most recent and relevant event to which future “state shifts” could be compared is the warm-cold-warm fluctuation in climate between 14,300 and 11,000 years ago.
These events, named the last glacial-interglacial transition, resulted in the extinction of half of the species of large-bodied mammals, and of other birds and reptiles, and a “significant decrease” in regional biodiversity.
Should the changes to the biosphere now underway result in a planetary “state shift”, the results would be similar “at a minimum”. Extinction rates are of particular concern, since after major bouts of extinctions it takes “hundreds of thousands to millions of years to build diversity back up to pre-crash levels”.
The global-scale forcing mechanisms operating today – identified by Barnosky and co as human population growth and resource consumption, habitat transformation, energy production and consumption, and climate change – all “far exceed, in both rate and magnitude”, the forcings of the last glacial-interglacial transition.
Barnosky and co say that key factors include “the conversion of about 43% of Earth’s land to agricultural or urban landscapes, with much of the remaining natural landscapes networked with roads”. This exceeds the change in the glacial-interglacial transition, when about 30% of the Earth’s surface went from being ice-covered to being ice-free. Another important point is the “drastic modification of energy flows through the global ecosystem”.
The already evident impacts on human society of biodiversity loss include “the collapse of cod and other fisheries”, “loss of millions of square kilometres of conifer forests due to climate-induced bark-beetle outbreaks”, the loss of carbon sequestration by forest clearing, and “regional losses of agricultural productivity from desertification or detrimental land-use practices”.
Barnosky and co argue that, if “critical thresholds” are crossed in biodiversity and species composition, much more serious disruptions would result – but also point out that no-one has yet worked out a way of telling how close such a leap into disaster is. “Criteria that would indicate exactly how close we might be to a planetary-scale critical transition remain elusive.”
In other words, human-caused biodiversity loss could reach catastrophic tipping points, but exactly how close we are to that, and how great the danger is, is very hard to say. This sounds similar to the situation with climate change, as I understand it: that the consequences of reaching tipping points would be devastating, but it is in the nature of ecological change that it is hard to predict how close they are.
The only rational course, in the face of such great dangers, is surely to steer away from them – and this is where the world’s governments, who are gathering in Rio this week, have failed so criminally.
Cardinale and his colleagues set out the progress made in researching biodiversity loss, and its effects on human society, over the past 20 years. They offer a summary of conclusions that can be drawn, including about four emerging trends, i.e.:
1. “The impacts of diversity loss on ecological processes might be sufficiently large to rival the impacts of many other global drivers of environmental change.” Recent experiments have shown that the impacts of species loss on primary productivity [i.e. the rate at which any ecological system produces biomass] is as great as the impact of drought, global warming, acidification, various forms of nutrient pollution, etc.
2. Diversity effects “grown stronger with time, and may increase at larger spatial scales” – suggesting the possibility of the type of accelerations to which Barnosky and co refer.
3. Maintaining multiple ecosystem processes at multiple times and places requires higher levels of biodiversity than does a single process at a single place and time (implying that no experiment can accurately replicate or forecast the global situation).
4. The ecological consequences of biodiversity loss can be predicted from evolutionary history.
Cardinale and co say that research has confirmed that the adaptation of ecosystems by society, e.g. to provide food, fibre and biofuels, has simplified ecological structures – and that this in turn has led to major losses of biodiversity.
However, while the role of human society in damaging biodiversity has been measured quite accurately, it is more difficult to track the opposite effect, i.e. the impacts of biodiversity loss on society, through damage to agriculture, humans’ environments, etc. “Critical questions remain” about whether, and to what extent, there is a feedback from biodiversity loss to “impaired ecosystem services”, Cardinale and co say.
What to do?
What to do about the crises of sustainability? The failure of the world’s politicians to get anywhere close to fulfilling the commitments made at the original Rio summit 20 years ago – on global warming, biodiversity, freshwater use and the rest – has been widely reported. And few people expect any meaningful action from them this time round. (See summit web site here.) [LINK]
What about the scientists’ view of action that should be taken? If Nature’s special issue is anything to go by, one of the loudest voices in academia on this subject is that of the biologist Paul Ehrlich, who in the 1970s made a reputation as an aggressive, Malthusian advocate of population control.
Ehrlich, together with Peter Kareiva and Gretchen Daily, argue in an article that population should be reduced by providing contraception to those who want it, and by education (they don’t say who might provide that and how). From Ehrlich this amounts to a modification of the arguments he made in the incendiary and polemical The Population Bomb (1968), which advocated compulsory, state-led population control. He may have shifted his argument partly because birth rates are falling quite steeply in a range of developed and developing countries, disproving the alarmist predictions of the 1970s.
Ehrlich and his colleagues acknowledge that “enormous inequity in wealth” must be dealt with along with “environmental hazard”. Rich countries account for the lion’s share of unsustainable economic practices, they say, quoting the International Energy Agency’s statistics showing that “developed” countries use 2-14 times as much energy per head as developing ones.
But the softening of Ehrlich’s pronouncements on the birth rate does not overcome the fundamental problem, i.e. his, and his colleagues’, insistence that addressing unsustainability is all about reducing the number of people, and reducing their levels of material consumption.
Although Ehrlich and co refer to the importance of “technologies, cultural practices and institutions through which each unit of consumption is generated”, as well as to the actual levels of population and consumption, they convey no sense that consumption is conditioned by the economic and social system. They give no hint of consumption’s relationship to production, and the capitalist economy’s remorseless need to expand production. Although they say that “rapid change […] to fundamental aspects of culture” will be needed to deal with unsustainability, their view of such change is incredibly conservative, and limited to what might be achieved within modern-day capitalist the social relations.
Moreover, Ehrlich and co offer the concept that “earth’s land and waters and their biodiversity can be seen as a capital stock from which people derive vital ecosystem services”. By imposing on the people-nature relationship the jargon of profiteering markets (“capital stock”, “ecosystem services”, etc) they put the whole thing into a chain of analytical shackles. With this approach, the way that those markets, and the power relations that lie behind them, shape both production and consumption – and in turn impact upon the people-nature relationship – can not even start to be examined.
It is unsettling, to my mind, that this modified Malthusianism seems to be quite widely accepted across academia. If radical and socialist voices are challenging this approach to sustainability on a methodological level, I have not come across them (and I’d be pleased to hear from anyone who has).
Our ideas about superceding capitalism and creating a society in which human creativity develops in harmony with nature, instead of at odds with it, would surely be strengthened by working on this. GL.
 Ehrlich and co refer to the IPAT formula, first put forward by Ehrlich in 1971, which says that society’s impact on nature (I) is a production of population size (P), per capita consumption (A, for “affluence”) and technology (T). There is a considerable body of literature about the problems with this formula. A survey of some of the debates, “The IPAT Equation and its Variants” by Marian Chertow, is downloadable here.