Remember the Deepwater Horizon drilling disaster? It’s been a few years now. This video is a brief update on some of our research on how the spill might have affected, and may still be affecting oysters off the coasts of Louisiana, Alabama and Florida. This has been very slow and difficult work, mostly because we have been monitoring the oysters for several years, and have had to develop protocols for the tissue analyses. But it is now moving toward publication.
In a recent opinion piece in Slate, Ben Minteer of Arizona State University continues to raise questions of the ethical legitimacy of collecting specimens for biological research. Minteer maintains that the risk to species, where population sizes might be small enough so that collecting represents a probabilistic extinction threat, outweighs the benefits to science and conservation. Unfortunately, Minteer is expressing an opinion, not the results of a carefully weighed and conducted analysis of data or facts. This is best highlighted by his example of the recent re-discovery of a species of New Guinea bat. Minteer states, “No scientist or conservationist today would deny the importance and value of describing a new species or confirming the return of one thought lost to extinction. But scientists also have a powerful ethical responsibility to minimize any and all adverse ecological impacts of their work.” Would that the world be so easily navigated. Today there are larger threats looming to biodiversity than at any time in the past 66 million years, and every one of those threats is the result of human actions. The threat of negative ecological impacts by scientists who are trying to document, explain and ultimately sustain what remains of the natural world pales hugely when compared to the threats of habitat destruction, the over-exploitation of species, and climate change. We will face very difficult decisions in the coming decades, and information is our friend, not our enemy.
Back to Minteer though. I think that his argument amounts to cherry picking and straw men. The reason for my position is best stated in a recent blog post by my colleague at the California Academy of Sciences, Dr. Jack Dumbacher. Jack explores the discovery of that very same bat picked by Minteer as an example, and he outlines very nicely the critical nature of the work. Please read his post. I’ll end here with an excerpt: “This study highlights the value of museum specimens in modern research, and the importance of taking specimens in modern field studies. Ironically, these studies were undertaken to assess the impacts of selective logging. The biggest threat to lowland forest in PNG is due to habitat loss from logging, mining, and oil palm conversion. One of the few things that might slow habitat loss is the fact that one little poorly known female bat was recently collected there.“
SCIENTIFIC COLLECTIONS PLAY VITAL ROLE IN CONSERVATION BIOLOGY
Today the UN and other organizations recognize the critical importance and threats to biodiversity around the world. The Species Alliance is recognizing the day by airing its documentary, Call of Life, on Free Speech TV (also streamed online). The documentary is followed by short interviews of myself (Peter Roopnarine), and Stuart Pimm. Please join if you can!
“Overpopulation is not the problem” goes a recent opinion piece in the New York Times by environmental geographer Erle Ellis. The core argument of the article seems to be that humans are unlikely to undermine ecosystems and ecosystem functions that sustain us. After reading the piece, however, I remain uncertain as to exactly which point the author wishes to prove. I question the article’s reasoning, (mis)representation of ecological concepts, and its historical interpretations.
Ellis launches his article by disputing any notions that disaster looms for humanity as our growing population threatens to exceed the Earth’s natural carrying capacity. His summary? “This is nonsense.” I agree, but only because the Earth’s natural carrying capacity is, in my opinion, a fuzzy and ill-conceived concept to begin with. I will point to a paper in Nature which I co-authored with a number of colleagues last year. There we argued that rapidly increasing human alteration of ecosystems, via species over-exploitation, landscape alteration, climate change and so on, threatens to push those ecosystems into a new functional state, most likely characterized by lower species richness and lessened ecosystem function. To the extent that humans depend on any of those species and functions, their loss will be felt. The notion of a finite carrying capacity for the planet is never emphasized in the article, however, because many of us involved do not believe that we have the necessary data to estimate that limit. Furthermore, arguments that ecosystems themselves represent an everlasting finite pie over which organisms must struggle are inconsistent with our record of the history of life on planet Earth. Geerat Vermeij and I make this very point in a recent article (see here). One view of life’s history reveals a stepwise increase in the quantity of energy fixed, transmitted and utilized by living organisms. So far not much to dispute with Ellis.
He immediately runs into trouble though as he wades into human prehistory, first pointing out, albeit correctly, that humans have a deep history of innovation, both social and technological, of exceeding the capacity of natural ecosystems to support human populations. The problem with this point is that it is only part of the story. Human societies have historically altered the environments around them to do things such as increase food production. Unfortunately, there are many examples in which either the alterations themselves initiated a slow and inexorable decline or change of environmental properties detrimental to the societies themselves, or the societies exhausted local natural resources on which they were dependent. Simplistic, blanket statements such as Ellis’ overlook too many of the intricacies and contingencies of human history. For example, the rapid rise of the Athenian Empire in the 5th century BCE was driven in part by the massive exploitation of natural resources to fuel Athens’ lucrative silver mines, and later the instrument of Athenian power, her super navy. As the trees ran out, the Athenians looked elsewhere for timber, coming to rely heavily on the kingdom of Macedonia to the north. Should I continue? There’s more than food at stake.
Ellis’ second point, and we’re still early in the article, is that humans learned over generations, as “their preferred big game became rare or extinct”, to increase the range of species on which they depended. And where is the evidence supporting the notion that the extinction of big game resulted in an increasingly diverse diet? In fact, if one wished to make the tenuous argument that it led to the domestication of cattle, wheat and so on, then one would have to concede that rather than increasing our repertoire of game, humans have in fact come to rely on a rather small and specialized subset of species. And in societies that did not do so, well, I believe that we refer to them today as hunter gatherers and nobody is too worried about their exploding populations.
The argument continues on to outline our ancestors’ triumphant climb to planetary dominance, claiming along the way that the Earth’s carrying capacity for prehistoric societies was probably no more than 100 million. As an ecologist, I have no idea what that claim is supposed to mean. Is the author claiming that if hunter gatherer societies had reached a total population of 100 million, that they would then have run into limits? Why? What would have limited them? Food production from natural ecosystems? Carrying capacity is far more than the amount of food out there. Species population sizes, humans included, are limited by more than just available food. There are other factors, driven by increasing population density, such as the more rapid spread of diseases, reduction of living space, good times for predators and parasites, and so on. And that brings me to the crux of what bothers me so much about this article, and that is the belief that we can continue to grow the human population without accumulating negative consequences, without risking the onset of additional and perhaps unseen negative consequences, without any reliance upon or concern for services provided by ecosystems, and with a blind belief that we will always innovate our way forward to address growing needs.
Thomas Malthus’ theory of exponential population growth does not claim that “population growth tends to outrun the food supply”. Malthus pointed out that without constraint, populations will indeed grow exponentially, but that growth is limited ultimately by the means and ability of the population to provide for itself. This is an important distinction. The idea that population growth is a driver of productivity, ascribed by Ellis to the economist Ester Boserup, should be interpreted carefully. Ellis interprets it positively, implying that population growth somehow facilitates productivity. Another interpretation of course is that population growth is a forcing agent of increased productivity because it applies constant pressure towards starvation. The fact is that the global human population has been growing approximately exponential since the 19th century, and certainly no earlier than that. The fact that some civilizations have supported substantial populations in the past, such as China and the Indian sub-continent, is indeed testament to the ability of human societies to organize and innovate to promote food production and security. But one should never lose sight of the dependence on the environment. Just ask the last members of the Tang Dynasty, whose final collapse was precipitated by the combined calamity of a breakdown of central authority and severe famine. Or the poor harvests during the final years of the Roman Empire. The margin for error is slim. In fact the history of China, trotted out as an example of population and productivity growth striding hand in hand, is punctuated by catastrophic famines and their socio-political consequences.
I suppose one could argue that technology will save us. This is indeed a possibility, and our global population, which has nearly doubled in my lifetime alone, is a fairly well-fed one. Many of the famines in the past century were caused as much by, or perhaps more by a lack of food security stemming from socio-political causes rather than environmental destruction. But predicting the future is a risky business, and simply saying that we can increase land productivity with existing technologies, and thereby never worry about rapid population growth, seems naive to me. I concede that I could be wrong, but I think that a far more likely scenario, given current trends and thinking, is increasing population size coupled with increasing per capita consumption, unrelenting domestication of natural spaces to support human consumption, degraded natural systems, and a globally declining quality of life. I stand with Ellis and others in the call for more sustainable means of production, but it is clear to me that sustainability cannot be achieved without proper protection and stewardship of Earth’s ecosystems. Perhaps there will be no starvation, but that will come at the cost of a world so transformed as to make the walls of the petri dish a wee bit more tangible.
I continue the series on the Tragedy of the Commons, based on my recent paper in the journal Sustainability.A tragedy of the commons (TOC) is initiated when one or more users of a common, and unmanaged, resource increases its use of the resource. Because the resource is a commons, all the benefits of increased use accrue to that user alone but the cost to the resource is shared by all users. According to Hardin’s argument, other users are then compelled to increase their own use, presumably to maintain their levels of benefit. This argument is generally accepted by TOC studies, whether they are for or against Hardin’s suggestions of the frequency of TOC or his suggested solutions. If one takes a historical view of any particular TOC, however, then there must have been a point when total utilization by all the users was below the level of resource available and the amount being produced (remember, the resource is renewable!). The question then arises, why, if one user’s increased utilization does not affect your own benefit because of the plenitude of the resource, would you feel compelled to increase your own utilization? There are assuredly multiple, non-exclusive answers, including the ability of humans to forecast situations. In that case, you could perceive a future limitation of your own benefits, or potential for growth, and therefore engage in a somewhat competitive escalation of resource use. No matter, because benefits are still accrued by yourself only, while costs are distributed among all the users. This perceived, or indirect cost can be measured in terms of the developing model (see previous post) as
where c is the average cost to each user. Any reduction of the standing resource available is a positive cost, while increases are negative costs. A stable resource level means that no cost is incurred by any users. I illustrate the situation with the following cartoons:
The situation changes significantly when total resource utilization reaches a point where individual user benefits cease to grow and actually begin to decline. Then, users are indeed compelled to increase use simply in order to maintain their current benefit. That is the classic TOC, but it leaves wanting the explanation for escalation of use prior to that point. I’ll take this up in the next post.
The first paper dealing with our Caribbean coral reef work is finally out. This paper is really just a detailed account of the data and webs compilation, but the data are now available to all. Enjoy!
Roopnarine, Peter D. and Rachel Hertog. 2013. Detailed Food Web Networks of Three Greater Antillean Coral Reef Systems: The Cayman Islands, Cuba, and Jamaica. Dataset Papers in Ecology, Vol. 2013, Article ID 857470, 9 pages.
Abstract: Food webs represent one of the most complex aspects of community biotic interactions. Complex food webs are represented as networks of interspecific interactions, where nodes represent species or groups of species, and links are predator-prey interactions. This paper presents reconstructions of coral reef food webs in three Greater Antillean regions of the Caribbean: the Cayman Islands, Cuba, and Jamaica. Though not taxonomically comprehensive, each food web nevertheless comprises producers and consumers, single-celled and multicellular organisms, and species foraging on reefs and adjacent seagrass beds. Species are grouped into trophic guilds if their prey and predator links are indistinguishable. The data list guilds, taxonomic composition, prey guilds/species, and predators. Primary producer and invertebrate richness are regionally uniform, but vertebrate richness varies on the basis of more detailed occurrence data. Each region comprises 169 primary producers, 513 protistan and invertebrate consumer species, and 159, 178, and 170 vertebrate species in the Cayman Islands, Cuba, and Jamaica, respectively. Caribbean coral reefs are among the world’s most endangered by anthropogenic activities. The datasets presented here will facilitate comparisons of historical and regional variation, the assessment of impacts of species loss and invasion, and the application of food webs to ecosystem analyses.
Here’s a new paper, hot off the press, in the open access journal PLoS One. Excerpt: “Scientists are amassing details about the scope and status of life’s variation at an accelerating rate. This aids our understanding of species’ distributions and their interactions over space and time. If we are to address the consequences of global environmental change for life’s future, however, biodiversity data must be aggregated, integrated and synthesized to a much greater degree than they are at present. Here, we call attention to a new community resource and tool which provides a step in the right direction.“
Large reductions in the abundance of exploited land predators have led to significant range contractions for those species…(read more here).
This is an extremely interesting new report by Boris Worm and Derek Tittensor. They compiled global range information for 13 species of large pelagic tuna and billfish, documenting significant range contractions in 9 of those species between 1960 and 2000. This implies that these top or near-apex predators have been extirpated over much of their range. Similar extirpations and extinctions of high trophic level terrestrial predators have resulted in now well-documented top down cascading effects, such as meso-predator release (no controls on smaller or less powerful predators) and subsequent declines of herbivore prey. It’s difficult for me to infer what the top down effects might look like in the ocean partly because of the tremendous ranges of some of these species and the likelihood of refuges, but also because, unlike most terrestrial predators, these species are exploited for food; as are the lower trophic level of meso-predators. We’re so busy knocking out the entire web that we could just be dampening many would-be cascades!