Termites may be hell in your house, but they help protect the rainforest from drought
Termites might be a huge pest in cities, but it turns out they serve a crucial role in tropical forests by making them better able to withstand drought.
And if it wasn't for an unexpected drought that hit Malaysian Borneo back in 2015-16, scientists would have never known how important termites are in these situations.
Dr. Kate Parr, a professor of tropical ecology at the University of Liverpool, and her colleagues had just set up a major forest manipulation study to quantify the role termites play in tropical forests when a super El Niño hit.
"At first, we were rather irritated or upset about this because we were wondering actually how much it was going to affect our experiment — whether it was going to cause a problem," said Parr in an interview with Quirks & Quarks host Bob McDonald. "In actual fact, it was very serendipitous and ended up as this wonderful situation where we were able to understand far more about this tropical forest because we had data from this drought period, but also the non-drought period afterwards."
Studying the termites' role in tropical forest ecosystems
Parr and her colleagues wanted to compare what happened in tropical forests where termites were present and where they were removed or suppressed. That way they could quantify what actually happens when you don't have termites to figure out what the termites were doing.
"To do this, we developed some novel methods to remove the termites. So this involves removing lots of termite mounds from our plots, so up to 80 termite mounds on a plot had to be physically removed, which is quite a challenge," described Parr. "And then there's a second thing we had to do it, which was really important because not all termites build termite mounds, and that was we had to put out poison food baits."
Parr said in their study, they wanted to figure out exactly what the termites were doing with the leaf litter on the ground.
"These termites eat all kinds of dead plant material and leaf litter is one of their favourite foods. And so, we were able to put out what we call litter bags. This is where you put litter in a little mesh bag and you put it out on the ground and you see how much was eaten at different periods of time. It allows you to quantify the decomposition rate — that is how quickly organic material gets broken down and removed."
After letting the termites do their thing for just over two years, the scientists made a few surprising discoveries.
The presence of termites meant there was a:
- 41 per cent increase in the decomposition of leaf litter
- 51 per cent increase in seedling survival rate
- 36 per cent increase in soil moisture
They also saw a "significant" increase in soil nutrient heterogeneity, which Parr said is how nutrients are distributed across the plots. "And that's thought to be really important because nutrient heterogeneity is strongly linked to tropical plant diversity."
But their most surprising finding about how important tropical forest termites are in their ecosystem is how they increase soil moisture during periods of drought.
"We know that some species in particular, can go very deep in the soil to bring soil moisture particles up," said Parr.
It really does seem like these insect groups can play really important roles.- Dr. Kate Parr, University of Liverpool
On top of that, when termites go out foraging, they often produce a crusty layer, often called "sheeting", on top of the leaf litter. It's a material made of soil particles stuck together with a bit of saliva.
"And it provides this sheeting or crusting, underneath which they can forage quite safely. And they can forage safely because they've got this buffered microclimate. It's more moist under there and they can not get eaten by ants. But the point of this kind of sheeting that they make on this forest floor, we think, is really important because, we think, it helps keep the moisture in the ground," added Parr. "Essentially, the water can't evaporate. It's kind of got this cap over it and we think that's how the termites increase the soil moisture levels."
Implications for logging and climate change
Parr said this is the first study to quantify the role termites play in their tropical forest ecosystems. "It really does seem like these insect groups can play really important roles."
Knowing that, what concerns Parr is that when tropical forests are disturbed — either by selective logging or other human activities — "that we start losing termites. Termites can't cope with disturbance. And this means that these forests are likely to be losing this resilience to these drought situations and other stressful environmental change, that they're going to be increasingly under."
As our climate continues to warm, droughts are going to become even more common than they are today.
"I think the role of termites is actually just going to get even more important."