Climate change could cause a household pest to increase its destructive course

When we think of termites, we might think of the danger they can pose to our homes once they settle in and start eating wood. But in reality, only about 4 percent of termite species worldwide are considered pests that may, at some point, eat your home.

In nature, wood-eating termites play a wide and important role in warm tropical and subtropical ecosystems. By feeding on wood, they recycle essential nutrients from the soil and release carbon back into the atmosphere.

Our new research, published today in Science, quantified for the first time how much termites love warmth. The results are impressive: we found that termites eat dead wood much faster in warmer conditions. For example, termites in an area with temperatures of 30 degrees Celsius will eat wood seven times faster than in a place with temperatures of 20 degrees Celsius.

Our results also point to an expanding role for termites in the coming decades as climate change increases their potential habitat across the planet. And that, in turn, could see more carbon stored in dead wood released into the atmosphere.

Deadwood in the global carbon cycle

Trees play a central role in the global carbon cycle. They absorb carbon dioxide from the atmosphere through photosynthesis, and about half of this carbon is incorporated into the new plant mass.

While most trees slowly grow in height and diameter each year, a small percentage die. Their remains then enter the deadwood pool.

Here the carbon accumulates until the dead wood either burns or decomposes through consumption by microbes (fungi and bacteria) or insects such as termites.

If the deadwood pool is consumed quickly, then the carbon stored there will quickly be released back into the atmosphere. But if decay is slow, then the size of the deadwood pool can increase, slowing the build-up of carbon dioxide and methane in the atmosphere.

For this reason, understanding the community dynamics of organisms that decompose dead wood is crucial, as it can help scientists predict the effects of climate change on the carbon stored in Earth’s ecosystems.

This is important as the release of deadwood carbon into the atmosphere could accelerate the rate of climate change. Storing it for longer could slow climate change.

Test how fast termites eat dead wood

Scientists generally understand the conditions that favor the consumption of dead wood by microbes. We know that their activity usually doubles with every 10 degrees Celsius rise in temperature. Microbial decay of dead wood is also usually faster in moist conditions.

On the other hand, scientists knew relatively little about the global distribution of deadwood termites, or how that distribution would respond to different temperatures and moisture levels in different parts of the world.

To better understand this, we first developed a protocol to assess termite consumption rates of deadwood and tested it in a savanna and rainforest ecosystem in north-east Queensland.

Our method involved placing a series of mesh-covered wooden blocks on the ground surface in a few locations. Half the pieces had small holes in the mesh, giving termites access. The other half had no such holes, so only microbes could access the blocks through the mesh.

We collected wooden blocks every six months and found that blocks covered with mesh with holes decomposed faster than those without, meaning that the contribution of termites to this decomposition was, in fact, significant.

But while the trial test told us about termites in Queensland, it didn’t tell us what they might be doing elsewhere. Our next step was to reach out to colleagues who could deploy the woodblock protocol at their study sites around the world, and they enthusiastically accepted the invitation.

In the end, more than 100 collaborators joined the effort at more than 130 sites in a variety of habitats on six continents. This broad coverage allows us to assess how wood consumption rates by termites vary with climatic factors such as mean annual temperature and precipitation.

Amy Zanne with student Mariana Nardi and postdoctoral fellow Paulo Negri from the Universidade Estadual de Campinas near termite mounds in the Cerrado tropical savanna in Chapada dos Veadieros National Park. Rafael Oliveira’s photo.

Termites love warmth and not too much rain

For wood blocks accessible only to microbes, we confirmed what scientists already knew – that decay rates roughly doubled in all regions for every 10 degrees Celsius rise in average annual temperature. Decomposition rates increased further where areas had higher annual rainfall, such as in the Queensland rainforest.

For the termite logs, we observed a much steeper relationship between decay rates and temperature – dead wood generally decayed almost seven times faster in areas that were 10℃ warmer than others.

To put this in context, termite activity meant that the wood volumes near tropical Darwin in Australia’s far north decayed more than ten times faster than those in temperate Tasmania.

Our analyzes also showed that termite consumption of wood blocks was highest in warm regions with low to intermediate mean annual precipitation. For example, termite decay was five times faster in a subtropical desert in South Africa than in a rainforest in Puerto Rico.

This may be because termites that are safe in their mounds are able to access water deep in the soil in dry weather, while flooding may limit their ability to forage for dead wood.

Termites love wood — and that includes the kind in your home.Shutterstock

Termites and climate change

Our results were synthesized into a model to predict how deadwood consumption by termites may change globally in response to climate change.

In the coming decades, we predict more termite activity as climate change projections show that suitable termite habitats will expand north and south of the equator.

This will mean that carbon cycling through the deadwood pool will become faster, returning carbon dioxide fixed by trees to the atmosphere, which could limit carbon storage in these ecosystems. Reducing the amount of carbon stored on land could then start a feedback loop to accelerate the pace of climate change.

We have long known that human-induced climate change would favor a few winners but leave many losers. It seems that the humble termite is likely to be one such winner, poised to experience a major global expansion in its primary environment.

This article was originally published on The conversation by Alexander Cheesman, Lucas Cernusak at James Cook University, and Amy Zanne at the University of Miami. Read the original article here.

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