Environmental Engineering Reference
In-Depth Information
Indicator
Facet of
Other data
Strengths
Drawbacks
sustainability
required
Biological
Population size
Biological
Relation to carrying
Simple measure, can indicate
Can be difficult to obtain. Gives no
capacity
level of depletion.
information on trends.
Population trend
Biological
None—a direct
Can use proxy for population
Need a robust and unbiased index, which may
measure
size; may be easier to measure
be hard to obtain. Need to have adequate
than size itself. Direct measure
power to detect change. Conservation action
of biological sustainability.
may be delayed until trend becomes obvious.
May indicate trend towards new equilibrium,
not unsustainable harvesting.
Population age/
Biological
May be more easily obtainable
Difficult to interpret—best avoided unless
sex/size structure
than population size.
strong harvesting selectivity is suspected.
Population
Biological,
Population size
Directly relates to the
Need to assume a functional form for density
productivity
financial
sustainable offtake level at any
dependence. Hard to measure in field,
given population size. Can be
allometric relationships may not be
estimated allometrically.
reliable.
Species
Biological
Trend or comparison
Measure of broader ecosystem
Same issues as for population trend. Power to
composition of
with other sites
health, may catch effects on
detect change in time to act likely to be low,
ecosystem
non-target species. Can use
especially for rarer species.
simple presence-absence data.
Hunter-prey interaction
Number caught
Biological,
Population size
Relatively simple to measure—
Ambiguous without an estimate of population
financial
needs to be measured as close
size. Measures from one point in time can not
to source as possible.
be used in isolation to estimate sustainability.
 
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