Climate change and a logic for updating opinions

Gavin over at RealClimate reports on a new poll by Zogby International that found Americans generally now believe that global climate change is real and has had effects on specific weather events like this summer's drought and hurricane Katrina.

RealClimate questions whether this change of opinion is in fact because of individual experiences or increased awareness of severe weather events, citing televangelist Pat Robertson saying it is the latest heat wave that finally convinced him. RealClimate speculates that when ideas are regularly before the public mind, for instance through the mass media, unexceptional events illegitimately cause or confirm changes of public opinion.

Of course, scientific inference generally does not proceed from isolated events, particularly from a single event. RealClimate underscores that scientists do not have a way of pinning particular weather events to overall patterns of climate change. Rather, it is changes in long run patterns -- frequency of hurricanes and so forth -- that is more appropriately attributed to climate change (and when observed in data provide evidence for the hypothesis). Gavin is correct about how evidence is brought to bear on scientific theories, at least in principle, or in what is sometimes called "rational reconstruction".

But is the probabilistic model for change of belief also the appropriate one for the change of public opinion? Perhaps there is room for unique events to cause a change of opinion. Where this occurs is precisely the situation we have in climate science: where we are presented with absolutely unfamilar experiences and seemingly preposterous explanations for them at the same time. I think the question turns on a difference between experiences -- which regulate the set of ideas we are willing to entertain -- and evidence -- which is meant to change our opinions about ideas already under consideration.

For background, assume only ordinary experience. No appeals to scientific knowledge are allowed. Now consider being presented with an absolutely preposterous hypothesis. The perposterousness of the proposition is fundamental. Adopting Bayesian terminology for the sake of convenience, our self-assessment of our own prior probability is near zero, or even zero itself. This is due to the immediate judgement that the proposition is preposterous.

If our prior probability is near zero it takes a great deal of evidence -- the kind scientists collect and report in scientific journals -- to change our opinion. If it is zero, our opinion cannot be changed at all. Further, non-scientists generally are not able to effectively evaluate claims to evidence put forth by scientists. What is one to do with information of unknown quality? Consider it circumspectly. It need not be that the public mind doubts the validity of a scientific claim, only that it does not know how to incorporate it into the accumulation of evidence or how to modify opinion accordingly. Thus, opinion will change slowly as the evidence accumulates.

Thus, for a theory (climate change) that has now been before the public for a period of time, the public, not knowing how to evaluate this information, finds its posterior probability on the proposition that the theory is true slowly shifting. Mixing metaphors from probability theory a bit, we will also say it has a broad posterior probability density. I will guess that posterior probability will shift much faster for scientists, who are used to entertaining all kinds of crazy ideas.

Now, back to experience. In the sustained presence of the new theory some experiences occur. I want to distinguish these anecdotal, subjective encounters with nature from the rigidly structured, quantitative encounters with nature that occur in research. These are experiences which in the absence of the theory (now before the public mind) would have seemed either unexceptional or inexplicable. In either case, they would have no bearing on one's belief about the theory. However, now there is a kind of fit (speaking loosely) between these experiences and the theory. They are a third category of events "possible evidences" (i.e. not unexceptional or inexplicable) which may or may not be linked to the phenomena postulated by the theory. It would require further consideration to know.

I think it is perfectly reasonable for this conjunction of a theory-before-the-public-mind and anecdotal evidence to cause the individual to revisit her prior probability. After all, the value assigned to this prior was just a self-assessment to begin with. What we might find is that a categorical change in the conceptual landscape changes the set of entertainable propositions. Then, after this post facto revision of the prior, the accumulated evidence chronicled in the journals and publicly disseminated by the media, which previously did not have very much effect, seems much more relevant and intelligible. This evidence now forces a change of opinion, after the facts of accumulated evidence have long been around, by having pulled the rug out from under the original defeator (its preposterousness).

Admittedly, this is a simplistic conception of belief change. Doubtless there are many ways in which qualitative evidence and different kinds of evidence are brought to bear on individual and public opinion. But, as a model, it is a bit more complex than the simple Bayesian approach and more insidious scientistic notions. Further, it makes intelligible observed patterns in changes in public opinion, particularly its lag behind scientific opinion. To a degree, it even justifies these lags.

In conclusion, I think it is perhaps a tad patronizing to conclude that "[I]t is probably overly optimistic to expect scientists... to have much success in conveying these finer points to the public directly. Instead, their skills are probably best used in clarifying these points to those (e.g. journalists, policy-makers) that set the dominant themes in the first place."

No doubt, however, it will require some thoughtful evidence brought by non-scientists to change the opinion of scientists on this point.

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Distributive justice and the ethics of species introductions

[This essay is adapted from a paper given at the Yale School of Forestry and Environmental Studies on January 24, 2005 as part of a forum on Invasive Species and the Public Good.]

Pressing problems pervade the topic of distributive justice and invasive species and not nearly enough thoughtful consideration has been given to them, in part because these questions represent the intersection of disparate ongoing discourses in many disciplines, including ecology and environmental science, economics, politics, and ethics. In many cases, we do not even know what questions to ask. I hope therefore that you will take my comments as an invitation to help us, our whole global society (because these questions are global in scope), to wrestle with the issues of invasive species in the environment, to ask the right questions, and to discover how we ought to address the environmental and social and ethical problems caused by invasive species.

The topic of this forum is “invasive species”. Nearly, but not entirely, synonymous with the word “invasive” are “exotic”, “weed”, and “alien”. Each of these terms enjoys some currency in social, legal, and scientific debates that relate to our topic. Not all introduced species are invasive. Many people, including myself, believe that many introduced species are beneficial, including livestock, agricultural products, garden plants, and sport fish. Many species in these categories, of course, evolved in places other than North America and were introduced here by Western Europeans. In order to avoid a merely terminological dispute, I will take invasive species to exclude these and other desirable introduced species. My reflections are restricted to those introduced species that are harmful.

But, here is where we encounter the first philosophical puzzle. What counts as harmful? It would be naïve to think that desirable or otherwise innocuous species cannot turn into harmful ones, either through evolution (a change in a species’ biology) or through changes in our systems of evaluation (a change in what counts as harmful to us), or even that species which are beneficial in one ecosystem or to one sector of society are not harmful in other contexts. So, we begin to see here, even at this early phase of our inquiry, that conceptualizing species introductions will be a knotty problem indeed. In order to get things going, I will suggest that the “harmful” part of “harmful introduced species” refers to a species that is harmful to some person at some time. We press on, therefore, now that we’ve established (somewhat) what we mean by invasive species, and turn our attention briefly to some ethical questions deserving of consideration. For the present, I want to exclude questions about possible animal rights—for instance, the possible right of introduced organisms not to be eradicated (one thinks of feral horses in the Western United States). I also want to bracket considerations about the legal or moral standing, rights of, or duties to protect so-called “natural” or “pristine” ecosystems to which species might be introduced, to biodiversity, to species threatened by invasive species, and the like. This is not because these problems are unimportant—they are important—but rather because there is so much we could say, and so many different sources to draw on for our reflections, that we would hardly arrive at anything useful if we set out from the beginning to understand the issue from this angle.

Instead, I will focus on ethical considerations as the problems of invasive species relate to our responsibilities to other people and to other peoples. The presuppositions of this kind of discourse are, of course, far more widely shared and I think we will find this approach gives us more than enough purchase on the problem. We will find out that there is in fact the possibility for injustices (among people and peoples). The possibilities for these injustices need to be schematized and investigated empirically to ascertain how serious these problems are. I suspect that they will be systemic. Only then can we expect to fruitfully explore opportunities for amelioration of wrongs already done and for proactive intervention for the future.

Thus, in order to gain some traction on the ethical issues posed by invasive species, we consider the different ways in which introduced species can be harmful. As a first pass, I propose the following threefold schema, which is not intended to be exclusive or exhaustive. To illustrate these we can consider as an example, zebra mussels, which were introduced into the North American Great Lakes, the largest reservoir of available freshwater on the planet, in the 1980’s.

The first way in which an introduced species can cause harm is by interfering with conservation. Our example species, zebra mussels, has been shown to threaten native clam species and possibly also the highly endemic crayfish fauna of the Southeastern United States, should it manage to become established there. Now, it might be thought that I have already violated my own prohibition to discuss only harms and benefits to people. Are not extinctions (and the possible right to persistence) harms to other species, namely those species which are threatened? Perhaps they are. But, they are more, too. Conservation always is a human endeavor (it is implied in the term—conservation is something we do; no other species are engaged in conservation). Thus, to the extent that introduced species interfere with the goals of conservation they have interfered with the goals of society. How much extinctions are harms to nature is very difficult to say, because we do not know how nature might value its species and ecosystems; that they are harms to people is clear however, and that we can evaluate the degree to which they are harms, if we choose, is also clear. This is the degree to which we find our cultures impoverished by species extinctions.

The second way in which invasive species cause harm is by interfering with production and with the potential for future production, which is an option value. Zebra mussels are notorious for colonizing the water intake pipes of power plants. The costs to the production of power are in the millions to hundred of millions of dollars annually. In this case, zebra mussels are a little unusual. More often, we think of invasive species interfering with agricultural production—for example: insect pests, weeds, aquaculture parasites, and timber pests like bark beetles—or else by interfering with natural resources that we regularly exploit, like fish stocks. So, the ways in which invasive species can interfere with production are various. Notice that different societies will be harmed differentially, depending on whether they are currently exploiting natural resources efficiently (as in most developed nations), or if the value of natural resources is primarily for their potential future exploitation (as is most developing nations).

The third way in which invasive species commonly cause harms is by interfering with human health, generally by creating the conditions for the propagation of disease. In the Great Lakes, it has been suggested that zebra mussels are linked to outbreaks of the bacterium Clostridium botulinum, the agent that produces the toxin causing botulism, and also to the concentration of PCB’s and other pollutants. Other invasive species, particularly biting insects like mosquitoes, are vectors by which infectious diseases are transmitted. And finally, still other species can be reservoirs for infectious disease.

Thus, in each of these ways, introduced species can interfere with the health and wealth of individuals, with corporate profits, and with social welfare. Interestingly, this underscores that the problem of invasive species is not, like so many other environmental problems, a conflict between environmentalists and corporate profiteers but an issue that confronts them both, for the same reasons, and for which reasons they ought to cooperate.
What’s more, we must recognize that what is designated by putting a box around “conservation” and “production” and “human health” is to a degree arbitrary. These distinctions are useful for conceptualizing the ethical problem. But, we know also that these are superimposed over an ecological landscape, into the ecological systems of which the introduced species is integrated and over which the introduced species may range. So, far from being exclusive categories, the harms causes by invasive species are interconnected through the ecology of the introduced species and a species which causes harms in one way can just as easily cause harms in the others.

So, in summary, the first question to be answered is this: How do invasive species cause harms to people? And, this is not a purely scientific question. Three important ways (and there may well be others) are by interfering with conservation, interfering with production, and interfering with public health.

Now, this scheme (or any alternative to it), of itself, does not represent any injustices. It does not, of itself, require ethical reflection or imply that there need be any normative imperative at all. However, the tight link between invasive species and welfare, signified by the several pathways of influence running from the introduced species through its ecology and its modes of harm to welfare—and welfare must also include such economically immeasurable benefits as clean air and water, freedom from infectious disease, and the ability to earn a living wage—this link implies a need for ethical reflection, because anywhere that welfare is distributed it can (and if unchecked by directed interventions, it will) be distributed inequitably. Thus, invasive species create a new problem for distributive justice. This is the distribution of exposure to environmental hazards and opportunities to exploit natural resources.

Thus, the next question I think we must answer takes the first few steps away from invasive species as a question for environmental science and toward questions of ethics. The second question is: How are harms from invasive species distributed? Conversely, the flip side of the question: Who benefits from the commercial and recreational activities that result in species invasions? Are these the same people who are harmed or are they different people? And how are the benefits distributed within the societies and peoples that benefit from trade and travel? Are they concentrated to a few individual fat cats or do they accrue to all the individuals in a society in the form of greater and better public services and more efficient economies? In some cases, it will turn out that the benefits are highly concentrated to a few individuals and the harms are distributed to society. This is external cost of production. In these situations the individuals harmed gain no benefit and very likely have their liberties and rights infringed upon. Under these conditions a “polluter pays” system may be appropriate, in which individuals responsible for introducing species are taxed or fined to pay the costs of redressing harms that result. But, in many cases, responsible individuals (or corporations) are difficult to identify, or both the harms and benefits are to society in general, a generic byproduct of our transportation infrastructure and systems of commerce, and in these cases there are no specific individuals who could be held legally or morally responsible.

It is interesting that there is already a discussion going on in this country and in others about the ethics and politics of the distribution of environmental damages. It is called environmental justice, and this movement to talk about environmental justice should be distinguished from environmental ethics, which is generally focused on things like the rights of animals, ecosystems, species, biodiversity, and the like. Now this discussion about environmental justice is focused almost entirely on the distribution of hazards and benefits among individuals within a society. This is a good and important thing to talk about. But, taking my cue from John Rawls’s essay The Law of Peoples [1], I wish to emphasize the importance of the distribution of environmental hazards and of resources among as well as within societies.

As a concrete example, we can consider the introduction of invasive species in ballast water, which exemplifies many of the relevant issues. Ballast water discharged from ships is one of the greatest sources of invasive species in marine and navigable fresh waters worldwide. To maintain trim and stability on the high seas, modern oceangoing vessels are designed to compensate for the lack of cargo by holding water in large tanks. This water is typically loaded when a ship is in port or operating in coastal waters. When cargo is loaded this water is discharged to compensate. Again, this usually occurs when the ship is docked. Any organisms that were loaded with the water and have survived the voyage are discharged into the new environment. It is generally believed that zebra mussels were introduced this way, as well as the introduction that touched off the American cholera epidemic of the early 1990s [2].

Now, discharged ballast water has the potential to move around tremendous numbers of organisms. Current estimates for a single ship are in the millions to billions of animals and of course untold numbers of microorganisms, including pathogens causing human and animal disease, and the algae that cause red tides. Moreover, ships, airplanes, and other vehicles of global transportation are able to more efficiently mix different communities of organisms than any other cause that I can think of. For instance, some ecologists tracked the path taken by a single ship during a 14 month period. It involved no fewer than eight trans-Atlantic voyages and one voyage from Asia to North America. Clearly, the combination of highly distributed trading patterns with the enormous numbers of individuals that can be introduced with each discharge of ballast water creates a scenario where the conditions for biological invasion are met on a regular basis. Indeed, ballast water is the dominant source of invasive species in most navigable waters.

But, do current patterns of ballast water discharge result in inequities, the kind of thing that requires ethical reflection? Reuben Keller and I have argued that that this is likely [3]. A naïve idea is that there are no inequities, at least among if not within societies, because societies that engage in trade might be expected to incur damages from invasive species in proportion to the value that they gain from trade. There are good reasons, however, to think that this naïve model is wrong. The ships that introduce the most ballast water are very large ships that deliver raw materials like wood chips, petroleum, and metal ores. These ships, unlike vessels that transport containers, are specially designed to hold bulk materials and consequently typically transport cargo only in one direction. Obviously, they transport ballast water in the other direction.

Often, the raw materials are derived from developing nations.

So, there is an asymmetry. Namely, we suspect that there is a net flux of goods to developed nations and ballast water to developing nations. These nations are already incurring opportunity costs by exporting unrefined raw materials to which considerable value will be added in developed nations. Thus, the ballast water situation represents a double injustice as societies in developed nations are profiting at two costs to developing nations: the opportunity cost incurred by not processing their own raw materials and the harms incurred by the introduction of invasive species in the process. To these we can add a third asymmetry or inequity: Although invasive species are the result of a global economy and systems for commerce, the responsibility for environmental monitoring and detection of invasive species and control and eradication of species once detected falls to individual nations, which are clearly differentially capable of dealing with these problems, a consequence of different scientific infrastructures and organization; capital for investing in long term environmental planning; and corruption and bureaucracy in the relevant government departments and ministries. For these reasons, among others, the problem of invasive species is a global problem, and one which if left to individual societies will continue to worsen. Of course, it is logically possible that all these nations incurring damages are being compensated fairly. However, based on the simple fact that many of these costs have not even been identified, I am inclined to think not.

So far, I have focused on distributional inequities among societies, between the developed nations which benefit from the trade in raw materials and developing nations which might incur the greater damages. However, there are likely inequities within these societies as well, between individuals that draw their livelihoods from commerce, and individuals who make the greatest use of natural resources, including subsistence farmers and fishers and poorer families that depend on environmental sources of fresh water. Invasive species introduced in discharged ballast water are unlikely to greatly harm industrialists and manufacturers, whose productive activities are insulated from the natural environment by factories, office buildings, and other features of the built environment. In contrast, invasive aquatic species disrupt food webs, injure fish stocks through parasitism and disease, and poison water sources. Thus, both among and within societies, the benefits and harms of invasive species are likely to be distributed asymmetrically. Further, the individuals benefiting from trade are the ones already making a profit and are unlikely to be the ones for whom invasive species incur costs in terms of future production.

We have so far not touched on the fundamental question of distributional justice: What is an equitable distribution of harms and benefits and how can existing inequities be redressed? Of course, this question is not unique to invasive species, but applies to all questions about environmental, economic, health, and social inequities and I believe that our ongoing discourse on invasive species could profit from greater reflection on themes well studied in these areas. Indeed, if we find (as I suspect) that approaches to distributional justice in these areas help to comprehend injustice that result from species invasions, then we may well be able to take advantage of existing legislation and other legal mechanisms for redressing injustice.

In conclusion, by narrowing our focus to include only invasive species, we have defined our project to include only those introduced species causing harms and anywhere there are harms there is the potential for injustice, if those harms are distributed unfairly. By focusing only on harms to people we have avoided predicating the ethical problem on controversial premises, like animal rights. I have suggested that there are three key questions that have to be addressed in any discussion of ethics involving species introductions. First: How do introduced species cause harm? Second: How are the harms and benefits of invasive species distributed at two levels: (i) among peoples, and (ii) within societies? Third: How can harms and benefits be fairly distributed (how do we know when the distribution is unfair?) and how can existing inequities be redressed and the entrenched systems that generate them reformed? I suggest that as this final question is not unique to invasive species, but extends to all questions about environmental, economic, health, and social inequities that we might make good use of existing conceptual frameworks for schematizing the problem and existing legal instruments for reforming environmental policy. Of course, it is only by continuing to foster a sincere and honest dialog, by educating policymakers and citizens, and by agitating for regulative legislation at national and international levels that we can hope for a better world in the future.

1. Rawls, J. 1999. The Law of Peoples. Harvard University Press.
2. World Health Organization. 1992. Weekly Epidemiological Record 67:33-39.
3. Drake, J.M. and R.P. Keller. 2004. Environmental justice alert: do developing nations bear the burden of risk for invasive species? Bioscience 54:718-719.

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The double bubble

According to Eric Weisstein's Mathworld, the double bubble is pair of bubbles which intersect and are separated by a membrane bounded by the intersection. A paradigm for math and physics, this inspiring form may also be investigated as a metaphor for the union of science and society, which are separate, but connected spheres of conceptualization, influence, theory, and action. I think of the public sphere as that ideal abstract space in which our identity and self-determination as a society are negotiated. In large part, science takes its shape from this space, but has its own existence in a space defined by the concepts, techniques and technology, and vocabularies of the special sciences. In modern technological societies the directional flux of ideas across the boundary from the public to the scientific sphere is crucial to maintaining the relevance and and social purposes of science, while the flux of ideas in the other direction is necessary for self-understanding in a technologically dominated world and contributes to a flourishing society. All too often, both fluxes are impeded by ideology.

Double Bubble

Image courtesy of John Sullivan

The purpose of this blog is to explore ideas about the relationship of science to society. It is to function as a transporter across the membrane of the double bubble, facilitating the flow of ideas. It is intended to be intelligent and serious, but not technical. For results pertaining to my research in ecology and environmental science, population biology, and epidemiology see my research blog. For a short bio and brief desciption of my research interests visit my webpage at NCEAS, the National Center for Ecological Analysis and Synthesis, where I work.

Part of the justification for a publicly accessible blog is to engage other scientists in the development and analysis of ideas about the purposes, ethics, logic and methods of technical inquiry. Another part is to solicit opinions from the American public (whose taxes pay for a great deal of the basic research performed in this country) and the global public (who have an interest in scientific developments and technology wherever it is produced and regardless of who pays for it). Therefore, through the investigation of specific points of intersection between science and society the reader is asked to explore more general questions. What is the purpose of science? What is the role of intellectual or academic or political freedom in the scientific enterprise? How should scientific findings affect our understanding of ourselves as individuals or as persons joined together in society? Is modern science relevant? When and how has research come to wrong conclusions? Depending on context, answers to these questions can probe the limits of shared scientific understanding and be of the highest importance to our self-understanding in the modern, technological world or might simply matter to my workaday life and that of other researchers with whom I share it, for instance on questions of research ethics or methods. At whatever level, fellow scientists and other interested persons are invited to participate.

Some details:

1. The opinions expressed on this webpage are my own and do not reflect official positions of my past, current, or future employers.
2. Comments to posts on this blog are welcome, but will be moderated. Inappropriate or gratuitous comments (positive or negative) will not be posted. Any serious ideas, however unsophisticated or developed, will be posted.
3. This blog is not anonymous (you know who I am - John Drake). The primary reason being that, in my view, ideas only have force when there is a person standing up behind them. This means inviting constructive criticism. There are times or topics for which anonymity is appropriate. This blog is not one of them.

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