Uses and Environmental Pollution of Biocides - Pesticides: Evaluation of Environmental Pollution - page 10

the end of the next century. Such increases in temperature have a number of implica-
tions for temperature-dependent insect pests (Palikhe 2007). Climate change may allow
pest migration or population expansions, which may adversely affect agricultural pro-
ductivity, profitability, and possibly even viability. Crop-pest interactions may shift as
the timing of developmental stages in both hosts and pests is altered. The majority of
insect pests that currently affect crops are likely to benefit from climate change as a
result of increased summer activity and reduced winter mortality. Some insect pests
that are currently present at low levels, or that are not considered a threat at this time,
may become more prevalent. The natural enemies of pests will have their own climate
optima, although not necessarily the same as their hosts. It is pertinent to ask whether
climate change will affect natural enemies to the same extent, or in the “same direction,”
as the pests they control (Thomson et al. 2010).
During the last three decades, agricultural pesticides have been increasingly recognized
for their adverse effects on the environment and human health. These external costs can
amplify due to climate change because pest pressure and optimal pesticide application
rates vary with weather and climate conditions. The possible increases in pest infesta-
tions may bring about a greater use of chemical pesticides to control them, a situation
that will require the further development and application of integrated pest-management
(IPM) techniques. Climate change may affect our ability to control pests. For example,
high temperature is reported to reduce the effectiveness of some pesticides. Humidity
levels can also modify their efficacy, as can the timing and amount of rain following their
application. On a simpler level, rain can affect the growers' ability to apply the pesticide at
the time when it is most needed, possibly an increasingly likely scenario. If pests are able
to complete more generations in a season, then this may lead to a greater pesticide use,
which in turn may lead to the more rapid development of pesticide resistance. Koleva et al
(2009) mentioned that weather and climate differences significantly influence the applica-
tion rates of most pesticides in the United States as farmers may grow different crops, use
different rotations, and change the intensity of management related to irrigation, tillage,
fertilization, and pesticide use.
The main climate drivers that change pesticide fate and behavior are thought to be
changes in rainfall season availability and intensity and increased temperatures, but
the effect of climate change on pesticide fate and transport is likely to be very variable.
Difficulty in predicting the long-term, indirect impacts such as land-use change driven by
changes in climate may have a more significant effect on pesticides in surface waters and
groundwater than the direct impacts of climate change on pesticide fate and transport
(Bloomfield et al. 2006).
The effects of climate warming on POP transport to polar regions have low certainty.
Sources of uncertainty include the dynamics of adsorption to snow and the extent to which
POPs currently trapped in sea and glacial ice will be released with warming.
Several studies have examined the interactive effects of climate and chemical contami-
nants on biota. Some of these studies suggest that climate change will increase the toxicity
of contaminants (Monserrat and Bianchini 1995; Capkin et al. 2006; Delorenzo et al. 2009)
or that contaminants will reduce tolerances to extreme temperatures (Heath et al. 1994;
Gaunt and Barker 2000; Lannig et al. 2006; Patra et al. 2007), perhaps because an organism
has finite resources to allocate for competing selection pressures (Rohr et al. 2003) and thus
multiple stressors tend to decrease the energy available for detoxification or temperature
regulation (Noyes et al. 2009). In contrast, there are several studies revealing that excretion
or tolerance of chemicals is positively associated with temperature (Maruya et al. 2005;
Paterson et al. 2007; Harwood et al. 2009; Weston et al. 2009; Rohr et al. 2010).