Posts Tagged ‘endangered species’

Estimating Endangered Species Interaction Risk with the Kalman Filter

March 22, 2014

Crossposting from the Reconhub:

AJAETogether with my co-author Stephen Stohs, I recently published an article in the American Journal of Agricultural Economics. The main gist is that with rare events like endangered species interactions, the statistical information in yearly data sets is limited, and that data from several years provide better information for decision making. We provide a method that is based on the Kalman filter and that allow for observations unequally spaced  in time. The method also takes account of spatiotemporal effects. We discuss the particular case of leatherback turtle bycatch in a gillnet fishery in California and Oregon. The leatherback is an endangered species, and in order to reduce bycatch, extensive spatiotemporal closures was imposed on the fishery in 2000. Our analysis shows that the interaction risk likely was smaller than in the scenarios that motivated the closures. To discuss whether the closures were and are warranted, require further analysis, however. As we discuss in the concluding section, closures in California may lead to trade leakages such that the total effect on the leatherback turtle stock is unknown. And the value of the leatherback in the ecosystem, and the value of its mere existence, is unknown.

The abstract:

To address the tradeoff between biodiversity conservation in marine ecosystems and fishing opportunity, it is important to quantify the risk of endangered species interactions in commercial fisheries. We propose a Kalman filter suitable for rare events to estimate the endangered leatherback turtle take risk in the California drift gillnet fishery in the years 1990–2010, conditional on spatiotemporal factors that affect take rates. Results suggest interaction risk has remained stable, but with substantial variation over the spatiotemporal distribution of effort. Our methods might also apply to recreation demand analysis with rare event risk, or to applications involving irregularly spaced observations, like trade-level stock market data.


Should we save the turtles?

November 1, 2008

Today I had an interesting discussion on endangered species with a fellow student (‘Clarabel’). The background for the discussion was that I am involved in a research project where we study a fishery along the coast of California and Oregon in which endangered Leatherback turtles are involved. The turtles sometimes get entangled in the nets used to catch swordfish and die from suffocation. The project I’m involved in questions the measures taken to protect the turtles from increased risk of extinction posed by the fishing activity. This seemed to provoke Clarabel; it is supposed to be obvious, on moral and possibly other (socioeconomic) grounds, that any step necessary to reduce risk of extinction is warranted (this is an overstated and simplified statement of Clarabel’s position, but that is not important here; I could probably have had the discussion with an evironmental activist with the given position). One funny thing was that when we talked about a species going extinct it represented a huge cost to society because a lot of people cared about species not going extinct. When talking about the effects of the protection measures (for example, putting fishermen out of business), however, the socioeconomic effects did not matter because higher (or deeper) moral and ethical principals about preserving the biological diversity came into play. I was not able to properly put my finger on the inconsistency while discussing. (I’m not too smart; I’m bad at talking and thinking at the same time, or is it listening and thinking again? Or was it listening I’m bad at? I keep forgetting.) I see it more clearly now, however (it seems obvious when the two statements are put next to each other). You cannot argue for protection with the social cost, and dismiss the social cost when it comes to saving, because protection and saving are, at least potentially, two sides of the same coin.

I just had another idea; environmentalists may argue that the social cost of a species going extinct is enormous since it applies to all subsequent generation of the human race. Any saving operation, however, at least any realistically conceivable today, would have a limited cost in comparison. Logic has it, then, that enormous costs are already inflicted on us alive today given that most species that has ever existed are already extinct. This cost will also fall on subsequent generations. First of all, personally, I do not feel tortured when thinking about extinct species (it would have been cool to see a T-Rex, of course). Second, one more extinct species would hardly make a difference.

Just for the record, I appreciate biological diverstiy and realize it’s important in the ecosystem we live in and depend on. If all human activities that represent an increased risk of extinction of any species were to come to an end, however, I’m afraid most of what we today think of as human activities would have to come to an end. We would live in caves somewhere in Southern Europe or Africa (and we would have to get rid of quite a few people since we would not be able to feed everyone). When considering protective measures of an endangered speices, we also need to consider whether our time, eneregy and resources could be put to better uses elsewhere and on other problems. And what if protecting one species would pose danger to another? A strategy to raise concerns about endangered species in the general population (on a global level) could be to raise the living standards in developing countries considerably as attention to environmental issues such as biodiveristy seem to be highly correlated with the standard of living. (This may be related to the phenomenon called the environmental Kuznets curve; emissions of carbon dioxide, for example, seem to curb with an increased income level; are people more aware of the environment when rich?) A question then would of course be whether the process of increasing living standards (almost) everywhere would threat so many species that it would be better to leave things as are. (It may even seem easier to reduce the standard of living of everybody back to the cave level instead.)

Picture from