362
The Biology of Sea Turtles, Vol. II
for “ecological extinction” (Jackson et al., 2001), the ecological value we gain from
sea turtles also diminishes. In another important ecological role, loggerhead eggs
have been shown to be the transport vehicle for high amounts of energy, nitrogen,
and phosphorus assimilated at sea and brought to nutrient-starved beach sands
(Bouchard and Bjorndal, 2000). The anthropocentric value assessment of these and
lesser-known ecological roles is that with fewer turtles, or with no turtles, there
would be ecological change in the appearance and function of beaches, of seagrass
pastures, and of reefs, and changes in the abundance of other organisms valued by
human beings.
The phenomena in which organisms take part have been recognized to have
value. Brower and Malcolm (1991) discussed value for the spectacle of monarch
butterfly ( Danaus plexippus ) migrations and overwintering aggregations and introduced the concept that these biological phenomena could be endangered by diminished butterfly abundance or by loss of behavioral traits. In a broad definition of
endangered biological phenomena (Brower, 1997), one might include the mass
nesting arribadas of Lepidochelys , the conspicuous passing-of-the-fleet migrations
of green turtles (Carr, 1954), and terrestrial (Whittow and Balazs, 1982; Garnett
et al., 1985) and shallow-water basking behavior (Felger et al., 1976) that may have
once been more widespread among green turtle populations. Arguably, these phenomena have nonconsumptive use value in their conspicuity. Thousands of olive
ridleys knocking together in their mass nesting, dense conspicuous passage of
migrating green turtles, and the prominence of turtles lying about on land can each
provide human observers with a grand experience, valuable either to those witnessing
it in person or to those viewing the event through broadcast media. These sea turtle
phenomena certainly have existence value. Many may place value in just knowing
that these phenomena take place, but another consideration is of the ecological value
from the effects of the phenomena themselves. For instance, the massive arribadas
of the olive ridley (Cornelius, 1986) and the formerly massive arribadas of the
Kemp’s ridley (Carr, 1967) provide a food and nutrient source — eggs and hatchlings
— that attracts and feeds multiple species of predators and brings nutrients for plant
growth during this concentrated pulse of reproduction.
14.5 SEA TURTLE SUPPLY AND DEMAND
A fundamental concept in economics is that rarity and increased demand drive up
the bid price of any given commodity. This concept has important consequences for
sea turtle conservation that differ between consumptive and nonconsumptive uses.
With consumptive use of sea turtles, use and marketing can create both a market
for increased demand and rarity in supply that results in an unsustainable removal
of turtles from the population. The resulting increase in consumptive use value may
or may not result in a force that drives sea turtle conservation. In fact, with no system
for regulated harvest among multiple harvesters, it is a rational economic decision
to take part in maximum-level harvest in anticipation of a short-term gain (Clark,
1973). Clark described this decision for “optimal extinction” as being economically
rational within the limited perspective of each individual harvester. In this perspective, profits from extirpated resources should be reinvested in other enterprises and
1123 book.book Page 362 Monday, November 11, 2002 11:11 AM
The Biology of Sea Turtles, Vol. II
for “ecological extinction” (Jackson et al., 2001), the ecological value we gain from
sea turtles also diminishes. In another important ecological role, loggerhead eggs
have been shown to be the transport vehicle for high amounts of energy, nitrogen,
and phosphorus assimilated at sea and brought to nutrient-starved beach sands
(Bouchard and Bjorndal, 2000). The anthropocentric value assessment of these and
lesser-known ecological roles is that with fewer turtles, or with no turtles, there
would be ecological change in the appearance and function of beaches, of seagrass
pastures, and of reefs, and changes in the abundance of other organisms valued by
human beings.
The phenomena in which organisms take part have been recognized to have
value. Brower and Malcolm (1991) discussed value for the spectacle of monarch
butterfly ( Danaus plexippus ) migrations and overwintering aggregations and introduced the concept that these biological phenomena could be endangered by diminished butterfly abundance or by loss of behavioral traits. In a broad definition of
endangered biological phenomena (Brower, 1997), one might include the mass
nesting arribadas of Lepidochelys , the conspicuous passing-of-the-fleet migrations
of green turtles (Carr, 1954), and terrestrial (Whittow and Balazs, 1982; Garnett
et al., 1985) and shallow-water basking behavior (Felger et al., 1976) that may have
once been more widespread among green turtle populations. Arguably, these phenomena have nonconsumptive use value in their conspicuity. Thousands of olive
ridleys knocking together in their mass nesting, dense conspicuous passage of
migrating green turtles, and the prominence of turtles lying about on land can each
provide human observers with a grand experience, valuable either to those witnessing
it in person or to those viewing the event through broadcast media. These sea turtle
phenomena certainly have existence value. Many may place value in just knowing
that these phenomena take place, but another consideration is of the ecological value
from the effects of the phenomena themselves. For instance, the massive arribadas
of the olive ridley (Cornelius, 1986) and the formerly massive arribadas of the
Kemp’s ridley (Carr, 1967) provide a food and nutrient source — eggs and hatchlings
— that attracts and feeds multiple species of predators and brings nutrients for plant
growth during this concentrated pulse of reproduction.
14.5 SEA TURTLE SUPPLY AND DEMAND
A fundamental concept in economics is that rarity and increased demand drive up
the bid price of any given commodity. This concept has important consequences for
sea turtle conservation that differ between consumptive and nonconsumptive uses.
With consumptive use of sea turtles, use and marketing can create both a market
for increased demand and rarity in supply that results in an unsustainable removal
of turtles from the population. The resulting increase in consumptive use value may
or may not result in a force that drives sea turtle conservation. In fact, with no system
for regulated harvest among multiple harvesters, it is a rational economic decision
to take part in maximum-level harvest in anticipation of a short-term gain (Clark,
1973). Clark described this decision for “optimal extinction” as being economically
rational within the limited perspective of each individual harvester. In this perspective, profits from extirpated resources should be reinvested in other enterprises and
1123 book.book Page 362 Monday, November 11, 2002 11:11 AM