EFFECT OF GLOBAL WARMING ON INSECT SURVIVAL
Hafiz Muhammad Arslan Abid*, Nasir Ahmed Khan, Sajjad Manzoor, Muhammad Tayyab, Muhammad Nasir, Muhammad Hamza
University of Agriculture, Faisalabad, Pakistan
*Corresponding author: [email protected]
Climate change is the most debated issue of time posing hazardous impacts on life on the earth. As most people know that temperature of our globe is rising from last few decades. Studies revealed that since 1850, 11 of the last 12 years are observed warmest most. Over the last 100 years, average increase in global surface temperature is by 0.7oC while maximum increase in temperature of 2-5oC has been observed near to the poles. Consequently, it is subsequent to increased ocean water level due to melting of polar ice, warmer and littler winters with prior onset of spring season and later arrival of winter periods. Generally, the warming is due to enhanced emissions of greenhouse gases (including methane (CH4), carbon dioxide (CO2), nitrous oxide (N2O) and chlorofluorocarbons (CFCs)) engendered due to burning of fossil fuels by human beings. For instance, atmospheric concentration of CO2 has amplified by 35% over the last 200 years and temperature is predicted to be increased by 1.8oC to 4oC.
Biologically, insects are cold blooded having body temperature similar to their environment. Thus only temperature can influence on insect behavior, development, distribution, reproduction and survival. It is believe that impact of increasing temperature on insects mainly overwhelms the effects of other environmental elements such as; it has been estimated through models that with a 2oC increment in temperature might result in 1 to 5 additional life cycles per season.
Rising temperature have already exerted influence on species distribution and diversity. For instance, in the United States and Canada Mountain pine beetle catastrophic forest pest has prolonged its range northward by about 186 miles with 1.9oC increase in temperature. Elevated CO2 will increase Carbon-Nitrogen balance in plants, which in turn will influence insect feeding behavior, defensive chemical concentrations in plants, competition between insect species and plant compensation responses to insect herbivory.
Due to hurried movement of people and goods, new insect species are arriving habitually to areas that are previously not reported to those insect species. However, rising temperature resulting in the survival of insects here that previously could not thrive. For instance, in the 20th century, potato psyllid a destructive pest migrated several times to California but usually persisted for a year only primarily due to winter cool temperatures that enforced this insect to flight to Mexico. Although, in 1999 or 2000, potato psyllid again migrated to California and established a large, year round population since that time and persisted there for the last 7 years. Resultantly, pepper, potato and tomato industries have underwent hefty losses.
Rising temperatures will bolster the survival of some insect species over others such as a 3oC rise in temperature would decrease 90% offspring production of important antagonistic beneficial wasps (Cotesia marginiventris) a common parasite of some caterpillar species. Thus, minor increase in temperature leads to debilitate the population of this beneficial insect and increase the damage by caterpillar species, and would likely to enhance pesticide operations.
Impact of increasing CO2 concentrations on plants is one of the most studied features of climate change and global warming. Carbon is the key element in plant’s structure so raised CO2 let them to nurture more quickly due to rapid carbon assimilation. For example, greenhouse growers have familiar this for a long time and many add CO2 deliberately to boost plant growth. Likewise, due to high photosynthetic rates in raised CO2, scientists initially supposed that it would be a remedy to world’s food security. Additionally, many crop plants would become more droughts tolerant along with growing more quickly because in elevated CO2 stomata do not need to be open as much.
Insects can be further affected due to disturbances such as plenty of carbon and lack of nitrogen that bring other major changes in plants. Mostly there are two kind of chemical defenses in plants that save plants from insect feeding i.e. carbon containing compounds like tannins and phenolics, and nitrogen containing compounds such as alkaloids and cyanogenic glycosides. Carbon based compounds decrease the insect’s food digestion capability often by binding with proteins such as cotton having phenolics that can reduce insect feeding. In atmosphere of raised CO2 concentrations, carbon based defenses increase in many plant species. While nitrogen based defenses either act as toxins and debilitate the insects or make the plants inedible by acting as repellents like potatoes and plums having nitrogen based defenses and under raised CO2 condition these plant defenses become reduced. So, the carbon and nitrogen balance will potentially influence insect’s feeding behaviors.
Pests and predators are potentially influenced by temperature. With the modification in temperature, behavior of predators can be stimulated or dispirited. For example, below 11oC, reproduction rate of pea aphid at which lady beetle (Coccinella septempunctata) can prey it exceeds while the situation is reversed above 11oC. On the other hand, at higher temperatures the natural enemies of spruce budworm (Choristoneura fumiferana) become less operative. Due to global warming, herbivorous insects may enlarge their ranges. Consequently, they could migrate to enemy free areas where their parasitoids may or may not track them. Monophagous parasitoids will be likely to most extremely effected having difficulty to adopt a new host.
Global warming is a serious challenge to agribusiness and our ecosystem as its consequences are hazardous to crop health. Rising temperatures will influence the insect behavior, distribution, development, survival, reproduction, geographical rang end population size and elevated CO2 on the other hand will alter the chemical plant defenses, parasitism, reproduction and insect developmental rates. Ultimately, these disturbances pose hazardous impacts on crop health and our ecosystem. A proactive and scientific approach will be required to cope with this issue. Recommendation of different tactics to manage the insects under changing climate scenario: modifying IPM, monitoring, modeling prediction, risk rating, genetic diversity and breeding for resistance. These strategies can be a promising program for crop health management and sustainable ecosystem from insects under changing climate.