The Baseline - Mining and the Environment: From Ore to Metal - page 352

FIGURE 8.3
Level of Biological Diversity Surrogacy

High Low

Characters

Individuals

Precision increases from the land-
scape to the character level, but cost
decreases and ease of measurement
increases in the opposite direction
Source:
Adapted from Williams 1996

Populations

Species

Assemblages

Ecosystems

Landscapes

Low High

Fish have been used for many
years to indicate whether waters
are clean or polluted.

Fish have been used for many years to indicate whether waters are clean or polluted,
doing better or getting worse. Knowing just whether i sh live in the waters is not enough -
we need to know what kinds of i sh are there, how many, and their health. Fish are excel-
lent indicators of water quality because they (1) live in the water all of their life, (2) differ
in their tolerance to amount and types of pollution, (3) are easy to collect with the right
equipment, (4) live for several years, and (5) are easy to identify in the i eld (EPA 2006).

Sentinel Species
One of the more difi cult aspects is the realistic assessment of the health impacts, once
environmental degradation is evident. Humans are exposed to low levels of contaminants
in their daily lives, but exposures may be over long, often lifelong, periods. The exposure
situation is usually complex, with environmental contaminants being present in mixtures
or coming from different sources.
Certain plants and animals can serve as sentinel species, indicators and early warners of the
impacts of environmental exposure. High trophic-level organisms (at the top of the food chain)
occupy a similar niche to many human consumers and are often exposed to similar types of
environmental contaminants through daily dietary intake. Many fundamental physiological
functions in wild animals and humans are similar. If a chemical at a certain concentration is
causing a certain effect in a wild animal, it could be taken as an indication of the same effect
occurring in humans. A substance that is neurotoxic to birds is very likely to be so to humans
and a substance that is estrogenic in i sh is likely to be so in humans. Trace metals in the envi-
ronment and their effects on wildlife provide a good example of this. The persistent and bio-
accumulative nature of some metals causes them to bio-magnify to high concentrations from
water in aquatic systems to the tissues of top predators. Evaluating the patterns, levels, trends,
and effects of metals in higher trophic-level consumers contributes to the understanding of
both the contamination of ecosystems and the risks posed to the health of humans and wild-
life. Even when the concentrations are below the limit of detection in water they may easily
be measured in animals. Wildlife examples have shown that some human groups may be at
increased risk because of their preferential habit of consuming i sh and other aquatic food.
A sentinel species can be selected for its ability to rel ect different types of environmental
disturbances. The best known example is perhaps the canary, which is sensitive to carbon
monoxide in the air and was used in underground coal mines as an indicator of potentially
toxic concentrations of this gas. Similarly, lichens are sensitive to sulphur dioxide and have
been used as indicators of SO 2 pollution around smelters and coal-i red power stations.

Certain plants and animals
can serve as sentinel species,
indicators and early warners of
the impacts of environmental
exposure.