uncertainty and where the consequences of a certain
action may represent a potentially severe or unpredictable
risk. The precautionary principle arose initially in
1970s German environmental legislation as the
“Vorsorgeprinzip,” regarding acid rain and justification
for energy tax policies (Boehmer-Christiansen, 1994);
“Vorsorgep” means foresight or anticipation with overtones of deliberated planning (Whiteside, 2006). At
a higher level, it was recognized in the World Charter for
Nature, adopted by the United Nations General Assembly
in 1982. It was subsequently incorporated into various
international conventions (CEC, 2000). This principle
was enshrined at the 1992 Rio Conference, during
which the Rio Declaration was adopted, whose Principle
15 specifies: “in order to protect the environment, the precautionary approach shall be widely applied by States
according to their capability. Where there are threats of
serious or irreversible damage, lack of full scientific
certainty shall not be used as a reason for postponing
cost-effective measures to prevent environmental degradation” (UN, 1992). Although without referring to the precautionary principle specifically, it is generally regarded
as the point of reference for this principle in the area of
sustainable development.
A major challenge is how and when to apply the
precautionary principle since social actors may want to
take advantage of a current lack of scientific evidence
to promote their own interests, misusing this principle
for demagogy or protectionism purposes (Gollier and
Treich, 2008). To avoid arbitrary decisions, the precautionary principle should only be invoked when three conditions are met: (1) identification of potentially adverse
effects, (2) evaluation of the scientific data available,
and (3) the extent of scientific uncertainty (CEC, 2000).
If the principle is invoked, the following points should
be considered: (1) measures adopted must be proportionate; (2) any decisions taken must be well founded, intelligible, and communicated; (3) measures adopted are
provisional, and, if proven to be unsuitable considering
new scientific findings, they should be adapted; and
(4) an evaluation of the consequences of inaction
(SFOPH, 2003). Decision makers, responsible for risk
management, may then decide how to act, depending
on the level of risk.
Bibliography
Boehmer-Christiansen, S., 1994. The precautionary principle in
Germany – enabling government. In O’Riordan, T., and
Cameron, J. (eds.), Interpreting the Precautionary Principle.
London: Earthscan Publications, Ltd.
CEC (Commission of the European Communities), 2000. Communication from the Commission on the Precautionary Principle.
Brussels: Commission of the European Communities.
Gollier, C., and Treich, N., 2008. Precautionary principle. In
Durlauf, S., and Blume, L. (eds.), The New Palgrave Dictionary
of Economics, 2nd edn. Basingstoke: Palgrave Macmillan.
Whiteside, K., 2006. Precautionary Politics: Principle and Practice
in Confronting Environmental Risk. Cambridge: MIT Press.
UN (United Nations), 1992. Report of the United Nations Conference on the Human Environment. Stockholm: United Nations
Conference on the Environment.
SFOPH (Swiss Federal Office of Public Health), 2003. The Precautionary Principle in Switzerland and Internationally. Bern:
Swiss Federal Office of Public Health.
Cross-references
Adaptive Management
Ecosystem-Based Management
Water Quality
PREDATOR–PREY RELATIONSHIPS
Judith S. Weis
Department of Biological Sciences, Rutgers University,
Newark, NJ, USA
Synonyms
Trophic interactions
Definition
A predator is an organism that eats another organism.
The prey is the organism that the predator eats.
Introduction
Intake of nutrients, i.e., eating, is essential in the long run;
avoiding being eaten is even more important in the short
term. Selective pressures often lead to an evolutionary
“arms race” between prey and predator, resulting in
improved prey capture by predators and antipredator
adaptations by prey species.
Trophic levels
The trophic level of an organism is the position it occupies
in a food chain. A food chain represents a succession of
organisms that eat another organism and are, in turn,
eaten. Food chains start at the first trophic level with primary producers (plants), followed by herbivores at the
second level, predators at the third level, and typically finish with top predators at level 4 or 5. The number of steps
that an organism is from the start of the chain is a measure
of its trophic level. The path along the chain can form
either a one-way flow or a more ecologically realistic food
“web” in which a particular species eats and is eaten by
a number of different species (Figure 1). The amount of
energy available decreases by about a factor of 10 at each
step.
Prey capture techniques and behaviors
Aquatic animals can acquire their food in a number of
ways: Filter feeders or suspension feeders strain
suspended matter and plankton from the water using
a specialized filtering structure. Animals that use this
method of feeding include attached and sedentary
496
PREDATOR–PREY RELATIONSHIPS
action may represent a potentially severe or unpredictable
risk. The precautionary principle arose initially in
1970s German environmental legislation as the
“Vorsorgeprinzip,” regarding acid rain and justification
for energy tax policies (Boehmer-Christiansen, 1994);
“Vorsorgep” means foresight or anticipation with overtones of deliberated planning (Whiteside, 2006). At
a higher level, it was recognized in the World Charter for
Nature, adopted by the United Nations General Assembly
in 1982. It was subsequently incorporated into various
international conventions (CEC, 2000). This principle
was enshrined at the 1992 Rio Conference, during
which the Rio Declaration was adopted, whose Principle
15 specifies: “in order to protect the environment, the precautionary approach shall be widely applied by States
according to their capability. Where there are threats of
serious or irreversible damage, lack of full scientific
certainty shall not be used as a reason for postponing
cost-effective measures to prevent environmental degradation” (UN, 1992). Although without referring to the precautionary principle specifically, it is generally regarded
as the point of reference for this principle in the area of
sustainable development.
A major challenge is how and when to apply the
precautionary principle since social actors may want to
take advantage of a current lack of scientific evidence
to promote their own interests, misusing this principle
for demagogy or protectionism purposes (Gollier and
Treich, 2008). To avoid arbitrary decisions, the precautionary principle should only be invoked when three conditions are met: (1) identification of potentially adverse
effects, (2) evaluation of the scientific data available,
and (3) the extent of scientific uncertainty (CEC, 2000).
If the principle is invoked, the following points should
be considered: (1) measures adopted must be proportionate; (2) any decisions taken must be well founded, intelligible, and communicated; (3) measures adopted are
provisional, and, if proven to be unsuitable considering
new scientific findings, they should be adapted; and
(4) an evaluation of the consequences of inaction
(SFOPH, 2003). Decision makers, responsible for risk
management, may then decide how to act, depending
on the level of risk.
Bibliography
Boehmer-Christiansen, S., 1994. The precautionary principle in
Germany – enabling government. In O’Riordan, T., and
Cameron, J. (eds.), Interpreting the Precautionary Principle.
London: Earthscan Publications, Ltd.
CEC (Commission of the European Communities), 2000. Communication from the Commission on the Precautionary Principle.
Brussels: Commission of the European Communities.
Gollier, C., and Treich, N., 2008. Precautionary principle. In
Durlauf, S., and Blume, L. (eds.), The New Palgrave Dictionary
of Economics, 2nd edn. Basingstoke: Palgrave Macmillan.
Whiteside, K., 2006. Precautionary Politics: Principle and Practice
in Confronting Environmental Risk. Cambridge: MIT Press.
UN (United Nations), 1992. Report of the United Nations Conference on the Human Environment. Stockholm: United Nations
Conference on the Environment.
SFOPH (Swiss Federal Office of Public Health), 2003. The Precautionary Principle in Switzerland and Internationally. Bern:
Swiss Federal Office of Public Health.
Cross-references
Adaptive Management
Ecosystem-Based Management
Water Quality
PREDATOR–PREY RELATIONSHIPS
Judith S. Weis
Department of Biological Sciences, Rutgers University,
Newark, NJ, USA
Synonyms
Trophic interactions
Definition
A predator is an organism that eats another organism.
The prey is the organism that the predator eats.
Introduction
Intake of nutrients, i.e., eating, is essential in the long run;
avoiding being eaten is even more important in the short
term. Selective pressures often lead to an evolutionary
“arms race” between prey and predator, resulting in
improved prey capture by predators and antipredator
adaptations by prey species.
Trophic levels
The trophic level of an organism is the position it occupies
in a food chain. A food chain represents a succession of
organisms that eat another organism and are, in turn,
eaten. Food chains start at the first trophic level with primary producers (plants), followed by herbivores at the
second level, predators at the third level, and typically finish with top predators at level 4 or 5. The number of steps
that an organism is from the start of the chain is a measure
of its trophic level. The path along the chain can form
either a one-way flow or a more ecologically realistic food
“web” in which a particular species eats and is eaten by
a number of different species (Figure 1). The amount of
energy available decreases by about a factor of 10 at each
step.
Prey capture techniques and behaviors
Aquatic animals can acquire their food in a number of
ways: Filter feeders or suspension feeders strain
suspended matter and plankton from the water using
a specialized filtering structure. Animals that use this
method of feeding include attached and sedentary
496
PREDATOR–PREY RELATIONSHIPS