Bjorndal and Bolten, 2003:

"Recovery goals should be set to population abundances at which sea turtles can fulfil ecological roles unless the remaining habitat is so reduced or degraded that this population level would not be large enough to ensure sufficient genetic diversity to respond to changing selective pressures.

An approach for identifying the population levels that fulfil ecological roles is reconstruction of past marine ecosystems and quantification of the roles that sea turtles played in those ecosystems.  These reconstructions would allow estimation of the abundance of sea turtles necessary to fulfil their ecological roles in the marine ecosystems of today.  As stated above, these population levels may be below pre-human levels because of the loss of habitat. (Under certain conditions, such as dramatic trophic shifts to jellyfish-dominated food webs, sea turtle abundance required to fulfil ecological roles could be above pre-human levels.)  However, the estimates of pre-human sea turtle population levels generated from prehistoric and historic evidence are essential to provide the proper perspective for evaluating the ecological roles of sea turtles.  Because the declines in sea turtle populations were so massive and occurred so long ago, it would be nearly impossible for modern biologists to imagine, and thus assess, the influence of past sea turtle populations on the structure and function of marine ecosystems without the historical perspective.  For example, without knowledge of the massive reduction in green turtles in the Caribbean, how could marine biologists realize that the Caribbean Thalassia pastures of today, characterized by long blades, extensive epibionts, and detrital-based nutrient cycles, represent a drastically altered state from the short-bladed, low-epibiont pastures of the past, in which grazing by green turtles dominated nutrient cycling?

Sea turtles (both carnivores and herbivores) were once key species in marine ecosystems.  We use the concept of "key species" in the sense of "species that are important to ecosystem structure and function in whatever form (e.g., biomass, abundance, productivity, or functional role), driving ecosystem processes or energy flows" (Piraino et al., 2002).  The decline in abundance of sea turtles and other megavertebrates initiated the collapse of marine ecosystems in which they lived (Jackson et al. 2001; Pandolfi et al., in review). Today, the degradation of marine ecosystems has accelerated as a result of continued overfishing, pollution, habitat destruction, and climate change with the result that higher trophic levels have been lost and microbial processes dominate an increasing array of marine habitats (Jackson 2001; Jackson et al. 2001; Pauly et al. 1998; Pitcher 2001).  Just as healthy sea turtle populations require healthy ecosystems, the reverse is also true.  Only when ecosystems are restored, can the ecological services and economic benefits that marine ecosystems provide to humans be fully realized (Costanza et al. 1997)."

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Citation and/or URL

Bjorndal, K. A. and Bolten, A. 2003.  From Ghosts to Key Species: Restoring Sea Turtle Populations to fulfil their Ecological Roles.  Marine Turtle Newsletter 100; 16-21. 

Spatial Coverage

International 

Temporal Coverage

200 years 

Update Frequency

Other Information

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