“Follow the Spiders”: Ecosystems as Early Warnings - Reducing Disaster: Early Warning Systems for Climate Change - page 333

Insects are regarded as an especially effective group of bioindicators for forest
health (Alves de Mata et al. 2008 ). As described by Maleque et al. ( 2009 ):
Ants, carabid beetles, and spiders can be used to infer the ecological suitability of forest
management treatments. Dung beetles and moths respond to habitat alterations caused by
forest fragmentation and can indicate the suitability of landscape-level forest management
techniques. Butterfl ies and cerambycid beetles respond highly positively to the presence of
herbaceous plants and understory trees and can be used to infer the integrity of thinning treat-
ments in forest management. Syrphid fl ies, which are strong fl yers associated with vegetation
complexity, can be used as bioindicators of landscape-level forest management practices.

However, studies of insect bioindicators rarely include verifi cation measures.
Thus, there remains a narrow range of scenarios and geographic regions for which
insect bioindicators have been fully developed (McGeoch 2007 as cited in Alves de
Mata et al. 2008 ).
Moving beyond single species, biotic indexes - assemblages of species and char-
acteristics - have been developed to monitor environmental status. The presence or
absence of families of macroinvertebrates, for example, can indicate chemical pol-
lutants in river systems (Chessman et al. 1997 ). Water quality can be assessed by
examining 11 aspects of corals including symbiont photophysiology and colony
brightness (Cooper et al. 2009 ).

18.3.1 Hazard Bioindicators

There is signifi cant evidence that climate change is having an impact on organisms
and biological processes, changing time of breeding and migration for example
(Walther et al. 2002 ; Ibanez et al. 2010 ). In Europe, changes in tree leaf color have
occurred later and later into the fall season, with an average delay of 0.3-1.6 days
per decade (Walther et al. 2002 ). Corals, in fact, have been referred to as the “canar-
ies” of the marine environment. They are excellent bioindicators of climate change,
as they are sensitive to above-average Sea Surface Temperatures (Sammarco and
Strychar 2009 ). Optimal growth of coral reefs occurs within 26-28 °C. At higher
temperatures, zooxanthellae ( Symbiodinium sp.), which inhabit corals and facilitate
coral growth, experience signifi cant mortality. Thus, with as little as 1.5 °C of global
mean warming, more than 95 % of corals may disappear (Caldeira 2013 ).
While bioindicators for climate change have been identifi ed, there are surpris-
ingly few studies of bioindicators for climate related hazards. The following section
briefl y describes examples of possible bioindicators for three hazards - droughts,
wildfi res and tropical cyclones.

18.3.1.1 Drought

According to Steinemann ( 2003 ), traditional drought indicators “are based on mete-
orologic and hydrologic variables such as precipitation, streamfl ow, soil moisture,
reservoir storage, and ground water levels.” As trees respond to many of these