Insect assault on plants may increase with temperature

Washington, Feb 13 (UNI) As modern temperatures continue to rise, it is believed the planet could see increasing crop damage and forest devastation by insects.

The researchers have drawn this 'may' conclusion after studying plants from Paleocene-Eocene Thermal Maximum.

More than 55 million years ago during the Paleocene-Eocene age, the rapid increase in carbon dioxide levels led to an increase in temperatures across the globe which possibly would have boosted the foraging of insects.

As modern temperatures continue to rise, the researchers believe the planet could see increasing crop damage and forest devastation.

The study conducted by researchers from Penn State, the Smithsonian Institution, the University of Maryland, the University of California, Santa Barbara, and Wesleyan University was published in Proceedings of the National Academy of Sciences.

''Our study convincingly shows that there is a link between temperature and insect feeding on leaves,'' said lead author Ellen Currano of Pennsylvania State University and the Smithsonian Institution. ''When temperature increases, the diversity of insect feeding damage on plant species also increases.'' The researchers gathered more than 5,000 fossil leaves from five sites representing time zones before, during and after the roughly 100,000 year temperature spike called the Paleocene-Eocene Thermal Maximum (PETM).

It was found that the PETM plants were noticeably more damaged than fossil plants before and after that period. The PETM plants, many of which are legumes -- the family that now includes beans and peas -- show damage with greater frequency, greater variety (such as mining, galling, surface feeding and other assaults) and a more destructive character than plants from the surrounding geologic time periods.

''This study shows that insects responded rapidly to a major change in climate during the PETM,'' said Enriqueta Barrera, program director in NSF's Division of Earth Sciences, which helped fund the project. ''This is in agreement with previous findings by co-author Scott Wing of the Smithsonian Institution who found that plants that previously were common much farther south migrated northward at this time''.

The study further saw if insect species feeding on the leaves changed over the time period. The analysis showed that what changed was the abundance of insect species that are highly specialized in the type of plant they consume and the way they consume it, such as leaf miners and gallers -- they are far more abundant in the PETM.

It is settled that insects in the tropics consume more plants and that warming temperatures are causing organisms to widen their ranges. In addition, research has shown that plants grown under higher concentrations of carbon dioxide are less nutritious, so insects must eat more plant tissue to get the same sustenance.

The study will help us prepare for further changes due to climate shifts and the probability of increased insect damage to plants with rising temperatures.

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