“Follow the Spiders”: Ecosystems as Early Warnings - Reducing Disaster: Early Warning Systems for Climate Change - page 335

have to be identifi ed and responses that occur prior to mortality, such as the shedding
of leaves, selected as indicators.

18.3.1.2 Forest Fires

In the topic Harry Potter and the Chamber of Secrets, Hagrid, one of the characters,
advises, “If anyone wanted ter fi nd out some stuff, all they'd have ter do would be
ter follow the spiders.” While this is fi ction, in reality, insects, including spiders, are
useful indicators of fi re events (Maleque et al. 2009 ). Insect damage can alter fi re
potential by changing the distribution of fi ne fuels (grass, fi ne woody debris, nee-
dles) and by altering forest structure, indirectly changing light, temperature, and
humidity conditions (Lynch and Moorcroft 2008 ). As insects kill trees, fuel loads,
including dead needles or branches, increase. Unlike live vegetation, dead fuels
have low water content (MC levels) and are highly fl ammable. Thus, risk of fi re is
increased.
The spruce budworm infestation in the forests of eastern Canada offers a well-
known example of the relationship between insects and fi re cycles. In 1987, Stocks
concluded that fi re potential increases in budworm killed balsam fi r stands. It
reaches its greatest level 5-6 years after infestation and decreases as balsam fi r sur-
face fuels decompose.
However, these fi ndings have recently been contested, as researchers have iden-
tifi ed other disturbances that mediate the impact of insects, infl uencing fi re potential
over time (Lynch and Moorcroft 2008 ). Simulations indicate that forest fi re severity
and extent have decreased over a 300-year period as a result of the interaction
between budworm, fi re, and changes in forest composition (Sturtevant et al. 2012 ).
In fact, forest management, including logging regimes, may have a greater impact
on fi re than insect infestations (James et al. 2011 ). Clearly the use of insects as bio-
indicators for fi re early warning is complex. Predictive potential will vary depend-
ing on site characteristics and history.

18.3.1.3 Tropical Cyclones

Potential bioindicators for tropical cyclones have also been identifi ed. According to
Paul and Routray ( 2013 ), coastal inhabitants in Bangladesh can predict the onset of
cyclones by observing the weather, the condition of the sea and rivers, but also by
observing the unusual behavior of animals. Observations of ants climbing walls
toward rooftops occur at least 1-2 days prior to a cyclone. The authors report that
34.1 % of total respondents interviewed (23.7 % of respondents in an inland com-
munity, 54.4 % of respondents in a shoreline community, and 39.5 % of respondents
in an island community) had the ability to predict cyclones and could even anticipate
cyclone intensity. They claim that indicators provide 2-3 days of lead time and
allow communities to take precautionary measures. However, knowledge varies