ABSTRACT
On average, Earth’s climate has warmed significantly (~0.6°C) over the last century, and additional rapid changes are anticipated (Houghton et al., 2001). General circulation models for assessing future climate, coupled to direct measurements, predict that atmospheric CO2 levels will continue to increase (Schneider et al., 1992; Vitousek, 1994). More locally, significant regional climate changes in the primary agricultural regions of North America are anticipated (Rind et al., 1990; Schneider et al., 1992; Schneider, 1993; Reddy and Hodges, 2000), including increased summer temperatures (4°C to 8°C), decreased precipitation, and a significant drop in available soil water (ca. 40% to 50%), each associated with a significant change in seasonality. Some analyses indicate that both environmental changes and system responses can
be sudden rather than gradual, further exacerbating the impact (Rietkerk and van de Koppel, 1997; van de Koppel et al., 1998; Alley et al., 2003; Gu et al., 2003). Human activity has greatly affected atmospheric concentrations of patterns of deposition of gaseous pollutants (e.g., SOx, NOx) that could affect insects in agro-ecosystems (Brown, 1995). In this context, important questions remain about responses of important natural and agricultural systems, including the issue of how agricultural pests and resulting food security will be affected. Diverse arthropod pests and plant pathogens significantly reduce agricultural production at present (Pimentel, 1991). How pests and their interactions with other organisms and the environment will respond to these changes, and whether such changes can be predicted is a big concern — one that requires consideration of regional and local climate changes that transcend global averages (Cammell and Knight, 1992; Lansberg and Smith, 1992; Harrington and Stork, 1995; Walther et al., 2002). The problem is complex and there are many possible ways that climate change from increased CO2 can affect the outbreak potential of insect herbivores in agricultural systems. In general, if CO2 continues to rise, average temperatures will also increase and precipitation will become more variable, suggesting that effects from temperature-dependent processes and plant responses to environmental stresses are the keys for understanding insect pests. One must also be cognizant of altered land use in the face of climate change as farmers and ranchers are likely to adapt and plant the most appropriate crops for new environmental and economic conditions.
