Who Would have Thought that the Very Hungry Caterpillar Could Cause Environmental Issues
Many of us have read and enjoyed the "Very Hungry Caterpillar" books to our children or our grandchildren but now scientists have found a new role for these creatures.
A study by Cambridge University in the UK has found that caterpillars play a surprisingly large role in causing greenhouse gas emissions.
They spend their days munching through carbon dioxide absorbing leaves while at the same time fertilizing CO2 releasing bacteria with their excretion. In normal gardens, this should not be a problem but their influence is felt when they feast in and around lakes where the microbes are prevalent.
Do they really cause harm?
Professor Andrew Tanentzap of the research team says:
"These insects are basically little machines that convert carbon rich leaves into nitrogen-rich poo. The poo drops into lakes instead of the leaves and this significantly changes the water chemistry. We think it will increase the extent to which lakes are sources of greenhouse gases".
The problem is that nitrogen-rich insect excrement (known as frass) can wash into lakes and act as fertilizer for microbes which then release CO2 into the atmosphere as they metabolize.
Even in the UK, the fear is that outbreaks of invasive caterpillars (such as from gypsy moths and forest tent moths) and that can occur every five years in forests, will promote the growth of greenhouse gas producing bacteria in lakes at the expense of algae that remove CO2 from the atmosphere.
How many leaves do these caterpillars eat?
A lot! They munch through so many leaves that the resulting decrease in leaf fall - and increase in excrement - has been found to alter the cycle of nutrients between the land and adjoining lakes on a large scale. Especially affected are carbon and nitrogen.
In addition, climate change has increased the risk of these "defoliator outbreaks" in forests which can result in even more CO2 being released from lakes. According to the University's research, those years with insect outbreaks can mean the leaf area of forests being reduced by an average of twenty two percent.
At the same time, the nearby lakes have a much higher percentage of dissolved nitrogen with a much lower percentage of dissolved carbon compared to non-outbreak years.
The Very Hungry Caterpillar
Meanwhile, that Very Hungry Caterpillar continues to munch his way into the hearts of young children worldwide whenever they come across his books. And those same children are always fascinated whenever they come across caterpillars on plants.
I find one of the the best places to find them is in a patch of nasturtiums - they seem to provide the perfect home every summer.