The projected increase in mean annual temperature due to global climate change ("global warming") should be expected to have a considerable impact on insects in Maine. Both physiological and ecological mechanisms are likely to be involved. Because insects are poikilothermic (or cold-blooded) animals, their development is strongly dependent on temperature. Therefore, for existing species a warmer climate may result in the increase in the number of generations per year, earlier occurrence in the spring, a reduction in winter mortality, and an increase in summer mortality due to heat stress and desiccation. Species that were previously excluded from Maine by low temperatures may become able to establish self-sustaining populations. At the same time, decreases in snowfall and snow pack may be detrimental for the organisms that once relied on this resource to insulate them from extreme weather.
Insects are also strongly dependent on interactions with other organisms on a variety of trophic levels. Differences in the pattern of response to temperature changes may alter relationships between insects and other members of an existing ecosystem. For example, an herbivorous insect may emerge from overwintering diapause before a sufficient number of its host plants become available, or a prey species may have a smaller increase in the number of generations per year than its predator, resulting in increased predation. The arrival of new species that are no longer excluded by low temperatures will also influence insect populations by supplying new resources and new natural enemies. On the other hand, the decline of species from a variety of taxonomic groups that are unable to adapt to new conditions may cause the decline of associated insect species, including the ones physiologically capable of functioning under the new temperature regime.
Overall, with rising temperatures we should expect an increase in the overall diversity of insect species with concurrent losses in local endemism. Currently, more species inhabit warmer areas of the world compared to colder areas. It is reasonable to suggest that a considerable number of them would expand their ranges into Maine once the climate becomes warmer. The fossil record from the previous periods of global warming supports this suggestion. Some of these new arrivals may cause a reduction in numbers or eliminate some native species through predation, parasitism, competition, etc.
The economic consequences of climate-driven changes in insect populations are difficult to predict. Most likely, there will be a significant increase in insect herbivory, both due to new pests arriving to Maine, as well as higher pest survivorship and growth rates. More pest generations per year would mean quicker evolution of resistance to insecticides. In addition, there could be declines in some pollinator populations. At the same time, we may also experience the establishment of new and more efficient natural enemies and pollinators. There could also be an increase in plant and animal (including human) disease due to higher vector activity and the establishment of new vectors.
(including human) disease due to higher vector activity and the establishment of new vectors.