Sebastian Troëng1, Jonas Ranstam2, and Eddy Rankin3
1 Caribbean Conservation Corporation, Apdo. Postal 246-2050, San Pedro, San José , Costa Rica
2 54D Uardav, SE-22471 Lund, Sweden
3 Tortuguero, Costa Rica
In recent years there has been considerable discussion in the sea turtle conservation community regarding the status of sea turtle species and the most appropriate methods to conserve sea turtles. The debate has become increasingly polarized with diametrically opposed positions being proposed by two schools of thought. One school calls for the complete protection of sea turtles and the other proposes sustainable extractive use of sea turtles as the preferable policy to achieve successful conservation. The two main battlegrounds in this controversy have been the classification of the status of sea turtle species in the IUCN Red List of Threatened Species and the proposals presented at CITES to downlist a hawksbill turtle population to Appendix 2.
Representatives of the two schools of thought have hotly contested the classification of sea turtles in the IUCN Red List of Threatened Species. Pro-protection groups have suggested that many species of sea turtles show negative population trends and therefore fulfill the criteria of population declines during the last three generations and hence should be listed as endangered and that some species should even be considered critically endangered. Pro-use groups have stated that there are plenty of sea turtles in the ocean and that there is little probability of any species going extinct in the near future.
Officially, there is no connection between the results of the IUCN assessments and the most appropriate strategy for sea turtle conservation. However, those in favor of absolute protection have seen the classification of the sea turtle species as endangered as support for their position. On the other hand, pro-use advocates suggest that if the sea turtle species do not fulfill the criteria of being endangered, then extractive use of sea turtles should be promoted.
In the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), there is a similar conflict. In the two latest Conferences of the Parties of CITES, Cuba has repeatedly requested a downlisting of the hawksbill population in Cuba from Appendix 1 to Appendix 2 in order to allow export of stockpiled tortoiseshell to Japan. The Cuban proposals have been vehemently defended by pro-use scientists, groups and countries and opposed with equal dedication by conservation organizations, pro-protection researchers and countries.
It can be concluded that proponents of both schools of thought have been unable to agree on the issues of status evaluation and conservation action. But does there exist an objective way to determine which of the two schools of thought is right?
The objectives of this paper are firstly, to analyze the value of population trends in identifying the most appropriate sea turtle management regime; and secondly, to suggest reconciliation between the two schools of thought that may help to forward sea turtle conservation through cooperation between proponents of the two conservation strategies.
What are trends? Population trends in sea turtles are most commonly recorded as the change over time in the number of nests deposited on a particular beach or the number of females arriving at the nesting beach each year. A trend in nesting is the result of interactions between many variables and processes. There are many important factors to consider. Biological factors comprise for example; density dependent effects on growth in feeding grounds and density dependent effects on hatching success at nesting grounds. Among environmental factors there are sand temperature that influence sex ratios, freshwater inflow and sediment load on feeding grounds (dependent on rainfall) that may be related to ocean climate cycles such as ENSO and climate cycles in the North Atlantic. Human use factors include management regimes and use patterns. A common trait of all these factors is that they may vary in time and in space.
Example of a trend – green turtles at Tortuguero. As an example of a trend we can look at the Tortuguero, Costa Rica, green turtle nesting trend. We used data from approximately weekly track surveys conducted along the entire Tortuguero beach (22 miles until 1994, when Jalova lagoon opened up and most nesting was confined to 18 miles of beach). We set end dates with 0 nests at June 15 and November 1 and then fitted a cubic polynomial function to each year’s track survey results. The resulting functions for each year were used to calculate daily (or rather nightly) numbers of nests and the daily totals were added up to yearly estimates of the total number of nests deposited. Regression of the ln of the estimated yearly totals was used to determine the nesting trend. The overall trend is a mean annual increase in the number of green turtle nests of 3.3% for the time period between 1986 and 2001.
So, is this positive trend due to successful protectionism? We do not think that can be stated with confidence. The trend is the result of the many factors mentioned above and others, acting over the past 25 years or more and throughout the Caribbean and beyond. Climate cycles, changes in management regimes, human use patterns and even the Nicaraguan civil war in the 1980’s may have influenced the Tortuguero nesting trend. It would be naïve to pretend that we know enough about sea turtle biology, human use and global climate to say that the apparent increase in green turtle nesting has been due exclusively to successful protectionism.
It would be equally naïve to pretend that our knowledge of sea turtle population dynamics is sufficient to use the trend to set an annual quota of green turtles that can be harvested/killed by Costa Rican fishermen and be sure that the fishery will not cause a population decline. This becomes even more apparent when we consider that there is a large capture of Tortuguero green turtles in Nicaraguan waters (Lagueux 1998).
Usefulness of trends in identifying successful management regimes. We have to acknowledge that trends in nesting populations are the results of a combination of many variables, some that we have more detailed information about than others. Our knowledge is currently insufficient to look at trends, which are the results of variables interacting over time spans of 25+ years and over large areas, and confidently determine the impact of specific management methods which may have been employed during only limited time and in only limited areas. Our ability to predict how the variables will interact in the future is even more limited, especially when we throw in global warming, climate change and rising sea levels into the already complex equation. Due to our incomplete understanding of the processes affecting population trends, there is enough room for the proponents of the two schools of thought to interpret trends at their own convenience so that the interpretation supports their position regarding sea turtle management.
Therefore, we have to conclude that the usefulness of trends is currently limited when it comes to deciding what management approach – absolute protectionism or sustainable extractive use – should be preferred.
If trends are currently of limited usefulness then what ways forward are there whilst we wait for the necessary knowledge to develop that will allow us to perfectly understand and predict the complex equations that control population trends? Reconciling the two schools. If we can reconcile the two schools of thought and develop a synthesis that satisfies both schools then at least we can put behind us the controversies of the IUCN Red List classifications and CITES and work together towards a common goal. This would prevent us from spending energy, time and funds on arguing over issues that we know we will not be able to resolve through currently existing mechanisms. We are sure that there are many excellent ideas for how reconciliation can be achieved so we will limit this paper to two possible options.
The goal of a protectionist conservationist, we would suggest, is to stop population decline by prohibiting extractive use of sea turtles. The goal of the proponents of sustainable extractive use, we think is to ensure that sea turtles like any natural resource will benefit people. A synthesis of these two goals could be what we would like to present as “Best Use.” The goal of “Best Use” is to develop non-extractive use of sea turtles as a means of providing benefits to people and at the same time protect sea turtles to ensure that there are no population declines.
Non-extractive “Best Use” includes using sea turtles as an eco-tourism attraction. An example is Tortuguero, where in 1999 a total of 20,885 visitors got permits to go on guided turtle walks (Troëng et al. 2000). The tourists spent on average US$57.6 per day for an average 4.1 days in Tortuguero (ICT 2000). The value of turtle related tourism is approximately US$4.9 million per year and local tour guides proudly state that a turtle is worth more to them live than dead.
We can contrast this value with the income from the turtle fishery that operated along the Caribbean coast of Costa Rica until 1999 and that permitted an annual take of 1,800 green turtles. The income from the sale of meat and eggs from one green turtle is estimated at US$198.7 (Troëng et al., in press). The total value of the fishery can therefore be estimated at approx. US$360,000 per year. In 1999, the fishery was stopped due to a lawsuit presented by several individuals and conservation organizations. The economic considerations and the concern about the impact of the rampant illegal fishing masked by the quota system, were important reasons for the court ruling that lead to the ban.
Another “Best Use” option could be using sea turtles as symbols, for example on T-shirts or in local artwork, as is the case in many sea turtle conservation projects around the world. The joint challenge for the future would be to cooperatively develop more non-extractive uses, for fishermen and others that are involved in extractive use of sea turtles. This is particularly important in feeding grounds and along migratory corridors, where to date there have been few non-extractive uses of sea turtles.
Future of sea turtle conservation. It still remains to be seen if there is enough interest and goodwill to reach reconciliation between proponents of the two dominant schools of thought. It is also too early to predict if the “Best Use” concept will be successfully applied in sea turtle conservation on a broad scale. However, we make the prediction that the sea turtle populations for which “Best Use” is implemented and the people depending on those turtle populations for their livelihood will fare best in the future.
David Godfrey and Jeff Mangel for constructive criticism on a draft paper. The Rankin family for conducting the track surveys used in the Tortuguero green turtle trend analysis. The Archie Carr Center for Sea Turtle Research for computerizing track survey results used in the trend analysis.
ICT. 2000. Plan de desarrollo turístico de Limón. Unpublished report to Instituto Costarricense de Turismo. 46 p.
Lagueux, C.J. 1998. Marine turtle fishery of Caribbean Nicaragua: human use patterns and harvest trends. PhD Dissertation. University of Florida, Gainesville. 215 p.
Troëng, SJ. Mangel, S. Ké lez, A. Myers, J. Kashner, L. Bell Chambers, D. Vizcaino, A. Rees, B. Amiteye, E. López, T. Moorman, Y. Rojas, L. Taylor, P. Angeloni, A. Morales, D. Quevedo, J.C. Melendez, J. Castro, and E. Rankin. 2000. Report on the 1999 Green Turtle Program at Tortuguero, Costa Rica. Unpublished report presented to Caribbean Conservation Corporation and the Ministry of Environment and Energy of Costa Rica. 46 p.
Troëng, S., C. Castro, L. Monterrosa, D. Campbell, and E. Hamorro. In press. Contingent valuation of green turtles Chelonia mydas in Caribbean Costa Rica. In: M. Coyne, comp. Proceedings of the 21st Annual Symposium on Sea Turtle Biology and Conservation. Philadelphia, PA, USA.
Abstract of paper presented at 22nd International Symposium, 2002