Species triage has been in the news lately. The reports might create the impression that we should give up trying to save the most threatened species. Let me be clear:
The science underpinning species triage does not say saving the most threatened species is pointless.
So, what does the science of species triage say? Well, you can read about some of it here and here and here. These links provide copies of the papers, but the one sentence summary is:
Species triage says we should spend resources in a way that saves the most species.
The slightly longer overview of triage is:
- With a limited budget, spend resources on species where the benefits are largest;
- Determine what is likely to be lost with the current budget even if it were spent as efficiently as possible; and
- Determine how many more species could be saved with increases in the budget.
Species triage recognises that conservation requires choices. If we have some money available that could be spent on, for example, two species, triage answers the question of how best to spend that money on each.
Triage also helps answer questions regarding other choices. For example, should we aim to prevent the extinction of all Australia’s bird species at the cost of approximately $10 million per year, or use that money for another four hours of defence spending? Which of those options would more efficiently protect Australia’s heritage?
The scientific literature tells us that the following attributes influence the optimal allocation of resources:
- The efficiency of management for each species. For example, with a given effort, what is the expected reduction in extinction risk for each species, taking into account the chance of success?
- The specific objective. For example, are we trying to minimize the number of extinct species or the number of threatened species?
- The relative value we place on species. Would we mourn the loss of some species more than others, or do we consider all species equal?
- The size of the budget; the optimal allocation of resources to species depends on what we have to spend.
I’ll illustrate the above four points with our analysis of Australia’s birds (McCarthy et al. 2008).
1. Using data compiled by Stephen Garnett on money spent on species and their changes in conservation status, we estimated how investment in each species changed their probabilities of decline and improvement. The findings were revealing.
First, the probability of extinction could be reduced with relatively modest investment in each species (e.g., the dashed line in the figure below). So it is not all doom and gloom; some investment in conservation in Australia has been remarkably successful. While we could surely do better, there are at least some clear benefits of management.
Example of probabilities of transition among conservation classes for a species versus total investment over an 8 year period. This shows how investment changes the probability that an endangered species becomes vulnerable (increases in abundance), becomes critically endangered (declines) or goes extinct. Approximately $50,000 per year ($400,000 over 8 years) reduces extinction risk of endangered species to near zero. Redrawn from McCarthy et al. (2008).
Second, and less happily, the data indicated that the probability of improving the conservation status of a species increased very slowly (if at all) with increased investment – the thick line in the graph above. So environmental managers in Australia seem quite good at reducing extinction of birds, but we need to improve our recovery efforts or make greater efforts.
2. The analysis also showed that the choice of objective influenced where best to focus effort. If the objective is to minimize the number of extinct bird species, it is actually optimal to invest in the most endangered species. However, we should invest in species with lower extinction risks for other objectives, such as when minimizing the number of threatened species.
3. Not all species are equal. Some species are valued more by society. It seems unlikely that Australians would spend as much money preventing the extinction of a plant louse than is spent on Tasmanian devils, even if I think the plant louse is the most important species in the world. Different people might value species depending on their taxonomic distinctiveness (i.e, how much evolutionary history they represent), their role in ecosystems, their charisma, or their potential to generate tourism revenue. These are all reasons why we might mourn the loss of one species more than another. And these relative values that are placed on species will influence how effort is allocated.
4. The size of the budget influences how money should be spent. Our analysis shows that even the relative amount of money spent on each species will change with the budget. For example, when aiming to minimize the number of threatened species (weighted by the level of threat), we should invest the most money in either endangered species or critically endangered species, depending on the size of the budget.
With Australia spending almost $30 million on bird conservation over an 8 year period, our analysis suggests that investing most heavily in the endangered and critically endangered species can be rational. However, changing the objective changes the optimal allocation among species.
Optimal investment in critically endangered (CR), endangered (EN) and vulnerable (VU) bird species when aiming to minimize the number of threatened species (weighted by extinction risk) in 8 years (solid lines) or 40 years (dashed lines) time. Results are show versus the total budget available in each 8 year period. From McCarthy et al. (2008).
So, what does this all mean? Species triage is not straight-forward. The optimal way to spend resources depends on numerous factors. One critical factor is the efficiency of management.
A second factor is what level of extinction we are willing to accept. As Stephen Garnett says, “the extent to which we conserve species says a great deal about who we are as a civilised society”. Our grandchildren would be justifiably appalled if a wealthy country permitted the preventable extinction of iconic species.
See also David Lindenmayer’s response to triage.
But species triage is confronting. It typically highlights that with current efforts, extinctions are inevitable*. That might seem like applying cold hard economics to decide which species we aim to conserve, and those we let go. However, in fact it is warm cuddly economics, because it allows us to maximize the number of species saved with the resources available. Indeed, doing anything else but applying triage is cold and hard, because it would allow more extinctions.
Triage compels us to determine what level of investment would be required to achieve acceptable levels of extinction. That allows us to make informed choices about trade-offs between conservation of species and other areas of national spending. In short, species triage is simply rational decision making (Bottrill et al. 2008).
* Edit: If we don’t like that answer, we need to increase the effort, not spend resources less efficiently!
Bottrill M. C., Joseph L. N., Carwardine J., Bode M., Cook C., Game E. T., Grantham H., Kark S., Linke S., McDonald-Madden E., Pressey R. L., Walker S., Wilson K. A. and Possingham H. P. (2008) Is conservation triage just smart decision making? Trends in Ecology & Evolution, 23: 649-654. doi: 10.1016/j.tree.2008.07.007 [PDF here]
Joseph L. N., Maloney R. F. and Possingham H. P. (2009) Optimal allocation of resources among threatened species: a project prioritization protocol. Conservation Biology, 23: 328–338. doi: 10.1111/j.1523-1739.2008.01124.x [PDF here]
McCarthy M. A., Thompson C. J. and Garnett S. T. (2008) Optimal investment in conservation of species. Journal of Applied Ecology, 45: 1428–1435. doi: 10.1111/j.1365-2664.2008.01521.x [PDF here]