260
The Biology of Sea Turtles, Vol. II
tropical to subarctic waters have been forgotten. Thus, sea turtles are victims of
the “shifting baseline syndrome” (Pauly, 1995; Sheppard, 1995). This pervasive
syndrome is the use of inappropriate baselines to assess population change or
stability. Referring to fisheries management, Pauly (1995) first described the syndrome as the tendency of scientists to use population levels at the beginning of
their careers as the baseline against which to measure population change. Pauly
stressed the importance of incorporating historical anecdotes of fish abundance into
population models of commercial fish species. For sea turtles, we do not have the
proper perspective, or a reliable baseline, against which to assess population trends.
For example, hawksbills ( Eretmochelys imbricata ) have been extensively exploited
for centuries for the keratinized scutes covering their shells, which are the source
of tortoiseshell or bekko (Parsons, 1972; Groombridge and Luxmoore, 1989; Meylan, 1999). Because populations were already greatly reduced or extirpated before
they were recorded, we have been unable to quantify past populations of hawksbills
and their ecological function.
Why is an understanding of the ecological roles of sea turtles important? We
propose three reasons.
1. Ecosystem function: To discover what we have lost in terms of ecosystem
structure and function. The far-reaching effects of removing consumers
from marine ecosystems have been demonstrated during the past decade
in a series of studies (Dayton et al., 1995; 1998; Jackson, 1997; 2001;
Pauly et al., 1998; Jackson et al., 2001; Pitcher, 2001). The fact that
humans have been “fishing down food webs” (Pauly et al., 1998) with
resulting widespread effects or trophic cascades is well documented (Jackson, 2001; Pitcher, 2001). Several studies have emphasized that current
problems — collapse of marine ecosystems and commercial fisheries —
are not only the result of recent events, but originate in prehistoric times
(Jackson, 1997; 2001; Jackson et al., 2001). These studies have generated
a new appreciation of the need to explore the characteristics of marine
ecosystems before human intervention. Paleoecological, archaeological,
and historical data are needed to reconstruct how marine ecosystems once
functioned (Jackson, 2001). The historical perspective gained from these
reconstructions provides essential guidance for restoring marine ecosystems and ensuring sustainable fisheries (Jackson et al., 2001; Pitcher,
2001). Restoring consumer populations to an abundance necessary to be
ecologically functional is still possible because most of these species still
exist, at much reduced levels (Jackson et al., 2001), with a few exceptions
such as the extinct Caribbean monk seal, Monachus tropicalis (LeBoeuf
et al., 1986).
2. Better understanding of environmental effects on remnant populations of
sea turtles: To understand how environmental changes today — either
natural or human-induced — may affect sea turtle populations. This understanding would greatly enhance our ability to make informed management
decisions. What effect would changes in the designation of allowable use
in zones of the Great Barrier Reef have on sea turtles there? What would
1123 book.book Page 260 Monday, November 11, 2002 11:11 AM
The Biology of Sea Turtles, Vol. II
tropical to subarctic waters have been forgotten. Thus, sea turtles are victims of
the “shifting baseline syndrome” (Pauly, 1995; Sheppard, 1995). This pervasive
syndrome is the use of inappropriate baselines to assess population change or
stability. Referring to fisheries management, Pauly (1995) first described the syndrome as the tendency of scientists to use population levels at the beginning of
their careers as the baseline against which to measure population change. Pauly
stressed the importance of incorporating historical anecdotes of fish abundance into
population models of commercial fish species. For sea turtles, we do not have the
proper perspective, or a reliable baseline, against which to assess population trends.
For example, hawksbills ( Eretmochelys imbricata ) have been extensively exploited
for centuries for the keratinized scutes covering their shells, which are the source
of tortoiseshell or bekko (Parsons, 1972; Groombridge and Luxmoore, 1989; Meylan, 1999). Because populations were already greatly reduced or extirpated before
they were recorded, we have been unable to quantify past populations of hawksbills
and their ecological function.
Why is an understanding of the ecological roles of sea turtles important? We
propose three reasons.
1. Ecosystem function: To discover what we have lost in terms of ecosystem
structure and function. The far-reaching effects of removing consumers
from marine ecosystems have been demonstrated during the past decade
in a series of studies (Dayton et al., 1995; 1998; Jackson, 1997; 2001;
Pauly et al., 1998; Jackson et al., 2001; Pitcher, 2001). The fact that
humans have been “fishing down food webs” (Pauly et al., 1998) with
resulting widespread effects or trophic cascades is well documented (Jackson, 2001; Pitcher, 2001). Several studies have emphasized that current
problems — collapse of marine ecosystems and commercial fisheries —
are not only the result of recent events, but originate in prehistoric times
(Jackson, 1997; 2001; Jackson et al., 2001). These studies have generated
a new appreciation of the need to explore the characteristics of marine
ecosystems before human intervention. Paleoecological, archaeological,
and historical data are needed to reconstruct how marine ecosystems once
functioned (Jackson, 2001). The historical perspective gained from these
reconstructions provides essential guidance for restoring marine ecosystems and ensuring sustainable fisheries (Jackson et al., 2001; Pitcher,
2001). Restoring consumer populations to an abundance necessary to be
ecologically functional is still possible because most of these species still
exist, at much reduced levels (Jackson et al., 2001), with a few exceptions
such as the extinct Caribbean monk seal, Monachus tropicalis (LeBoeuf
et al., 1986).
2. Better understanding of environmental effects on remnant populations of
sea turtles: To understand how environmental changes today — either
natural or human-induced — may affect sea turtle populations. This understanding would greatly enhance our ability to make informed management
decisions. What effect would changes in the designation of allowable use
in zones of the Great Barrier Reef have on sea turtles there? What would
1123 book.book Page 260 Monday, November 11, 2002 11:11 AM