“Follow the Spiders”: Ecosystems as Early Warnings - Reducing Disaster: Early Warning Systems for Climate Change - page 332

Table 18.1 Possible criteria for selection of bioindicators
Criteria Defi nition
Specifi city Biological response is specifi c to the stressor of interest and not to other
environmental stressors
Monotonicity The magnitude of the biological response should refl ect the intensity and
duration of the stressor of interest
Variability Biological responses should be consistent at a range of spatial and temporal
scales. Ideally there should be low background variability, although a
change in variance can itself be used as an indicator of an impact
Practicality Measurements of biological responses should be cost effective, easy to
measure, non-destructive, and observer independent
Relevance Biological response should be ecologically relevant and important in public
perception to assist communication
From Cooper et al. ( 2009 ), which is based on Jones and Kaly ( 1996 ), Erdmann and Caldwell
( 1997 ), and Jameson et al. ( 1998 )

(Kotwal et al. 2008 ). It can be extremely diffi cult to identify bioindicators in
every biogeographic zone.
Individual plants or animals (of a given bioindicator) may vary in sensitivity, and
sensitivity can evolve. The Bel W3 variety of tobacco is sensitive to ozone, a major
tropospheric pollutant in the summer, and has been used as a bioindicator since the
1960s. Leaf damage or necrosis occurs at specifi c threshold levels - 30 ppb for
plants exposed for 8 h (Larsen and Heck 1976 from Verge et al. 2002 ). However,
some plants are more sensitive to ozone than others, and a variety of secondary
phenomenon (chemical, physiological, and pathological) can interact to induce or
limit damage (Verge et al. 2002 ). Every bioindicator should therefore have a test
allowing its sensitivity to be assessed. This is especially important for bioindicators
used in the wild and subject to diverse conditions (Verge et al. 2002 ).

18.3 Examples of Bioindicators

Despite some of these challenges, a variety of bioindicators are currently in use.
As mentioned, the Bel W3 variety of tobacco is used to help monitor ozone.
Roadside Rhododendron pulchrum can be used to detect traffi c-related heavy metal
pollution (Suzuki et al. 2009 ). Heavy metals (Pb, Ni, and Zn) are signifi cantly
correlated in roadside soil and Rhodedendron leaf samples, when analyzed in a
laboratory using inductively coupled plasma optical emission spectroscopy or
inductively coupled plasma mass spectroscopy (Suzuki et al. 2009 ). In addition to
fl ora, fauna - specifi cally charismatic species - can indicate environmental change.
In the 1950s, population failures of bald eagles ( Haliaeetus leucocephalus) and
peregrine falcons ( Falco peregrinus ) alerted the public to the dangers of chlorinated
hydrocarbon pesticides (Burger 2009 ).