Could the planet experience a surge of insect migrations toward temperate climes brought on by the milder temperatures of a warming planet? The modern-day example of malaria-carrying mosquitoes moving to regions once too cool for them to survive is a telling precedent of what could come. Now, scientists studying another ancient climatological shift reported earlier this week that insects back then not only moved further afield, they also ate more plants and did more kinds of damage to them.
Scientists speculate that 55 million years ago, a massive volcanic eruption or fires caused carbon dioxide levels to rise, resulting in a 9-degree Fahrenheit increase in global temperature over the course of 5,000 years — an event known as the Paleocene-Eocene Thermal Maximum. The earth remained warm for 100,000 years before cooling down, but not before atmospheric carbon dioxide tripled, making plants less nutritious and forcing swarms of tropical and subtropical insects to move into now-warmer temperate zones in search for food. Looking at the fossil record left in the badlands of Wyoming, the study found that the insects were more devastating for plants: they mined the leaves, eating whatever they could on the surface; laying eggs inside leaves resulted in a reaction called "galling" where the affected area swells into a tumour upon which the young insect will feed.
"As far as insect feeding goes, during this time the number of types of damage is higher and also we see almost a doubling in the frequency of leaves being damaged," says Ellen Currano of Pennsylvania State University and the Smithsonian Institution, who authored the study's findings by examining fossils over a period of 4 million years.
The long-term analysis allows for parallels that could be drawn with today's current situation, where according to the IPCC (Intergovernmental Panel on Climate Change), temperatures could rise anywhere from3.2 to 7.2 degrees F (1.8 to 4 C) by the year 2100 — a much faster rate of increase.
Currano adds: "Our study convincingly shows that there is a link between temperature and insect feeding on leaves. When temperature increases, the diversity of insect feeding damage on plant species also increases."
::Environmental News Network
Images: Ellen Currano