Victim of changes

14/10/1998
Down To Earth

Victim of changes GLOBAL warming. The most talked about phenomenon of the new century, merely means that increasing concentration of greenhouse gases such as carbon dioxide (CO2) and several others are trapping the heat radiated by the Earth, leading to a warmer planet. This can have many unpredictable outcomes, and climate change is one of them. As the planet heats up, we might experience unprecedented changes in the world's climate. Effects of global warming will not be restricted to climate alone. For changes in the climate will affect lifeforms that inhabit our once-green planet. And that, agree experts might change a whole lot of other things, it's called the dornino effect: when one change triggers several more, finally leading to a whole chain of unforeseen events arising because of the first. And no one knows for sure what exactly will be the effects of climate change and increased concentrations of CO2 and other greenhouse gases.

According to a Florida-based biologist, high CO2, levels may have some very surprising consequences for plant-eating insect species. While continually rising levels of CO2 might make the plants grow faster, they could mean bad news for the plant-eating insects. Peter Stiling, a biologist at the University of South Florida in Tampa, USA, has discovered that subtle increases in CO2 can kill leaf-eating moths by reducing the nutritional value of the leaves - their staple diet.

He says the new research contributes to the mounting evidence that the ecological changes brought about by rising co2 levels are likely to be hard to predict "It looks like elevated CO2, has at least as many direct effects as indirect effects," Stiling says.

He looked at several species of mining moths, whose larvae tunnel through leaves for food. By examining the tunnels, or "mines", they left behind, Stiling and colleagues could tell whether the larvae had died inside the mine, were killed by predators such as spiders or ants, or were eaten from the inside out by the larvae of parasitic wasps. Stiling conducted the experiment at the Kennedy Space Center in Florida in 16 open-topped chambers containing myrtle oak and sand-live oak. Half of the chambers had normal CO2 levels, while the other half had approximately double the normal CO2 level. Stiling found that many more larvae died in the chambers with high CO2 levels. About 10 per cent of the larvae in the high CO2 chambers died inside the mines, compared with only five per cent in the chambers with normal CO2 levels. The deaths within the leaf mines probably resulted from malnutrition, Stiling says. Plants in high CO2 conditions grow bigger and faster, but their lower nitrogen content makes them poorer nutritionally.

Many more high CO2 larvae fell victim to parasites as well. Stiling says the reason is probably related to poor nutrition.

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