Climate change will increase termite activity, releasing more carbon dioxide

Termites could contribute to a climate feedback loop as their environments become hotter and more arid.

A recent report, published in the journal Science, found that the wood decaying activity of termites will increase by around 6.8 times for every 10⁰C the Earth warms. 

Rising temperatures will cause areas of the world to become significantly drier, allowing termites to increase their activity and release more carbon stored in deadwood back into the atmosphere.

Dr Paul Eggleton is a Merit Researcher at the Museum who specialises in termites and co-authored the report. He says, 'Rising temperatures will affect the fate of deadwood in semi-arid areas. Termites don't perform too well if it's cold and dry but will do better as the world gets hotter.'

'The amount of wood being broken down in these environments will increase considerably, and that will have significant implications for the overall carbon budget of the globe.'

Climate change could also change the species composition of ecosystems around the world as wood-eating termites become more prevalent.  

What are termites?

Termites are a group of around 3000 species of insects which are estimated to have first evolved from cockroaches around 195 million years ago during the Early Jurassic, though the first confirmed fossils of the group date from around 50 million years later.

They are thought to be one of the earliest groups of social insects, such as bees and ants. Termites live together in colonies with sterile workers performing a variety of roles to support reproductive individuals such as queens.

These colonies have spread to many areas of the world, with hotspots in the tropics and subtropics. Over a third of the world's species of termites live in Africa, with significant numbers also found in Australia, South America and Asia.

Europe has very few native species, and while no species of termite is endemic to the UK, the insects are periodically found in the country, most likely imported accidentally in wood and wood products.

While many species of termites eat other plant material, and even soil, wood-eating termites are generally the most well-known.

Termites are among only a few organisms that are able to degrade cellulose, a compound found in wood that provides its strength and is very resistant to degradation. Wood-eating species have specific adaptations and relationships to enable them to break it down.

'Termites break down deadwood in a lot of different ways, but the first thing they do is use their powerful mandibles which allow them to tear strips off the wood,' Paul says. 'In their foregut, they have a grinding structure called a proventriculus which allows the wood to be broken down even further so that its surface area to volume ratio increases.'

'This allows a group of symbiotic microbes that will help them feed on the woody material, as though termites can break down deadwood alone, they really need the help of these microbes to do this completely so that they can survive on deadwood. It's this partnership between them that make it such an effective system.'

This ability makes termites an important part of the world's ecosystems. They form part of the carbon cycle as they, alongside free-living microbes and fungi, release stored carbon in deadwood back into the atmosphere as carbon dioxide. 

If their activity increases, then more carbon dioxide could be released from these stores, exacerbating climate change. As a result, it has become increasingly important to understand how termites will behave in the Anthropocene. 

How will termites be affected by climate change?

To assess how termites could be affected by rising temperatures, the researchers conducted a wood decay experiment at 133 sites around the world. Blocks of pine wood were monitored for up to four years for signs of termite activity, with some able to be accessed by termites while others were not.

They found that greater evidence of termite activity was found in areas which were hotter and drier, with termites present in around half of the blocks when temperatures were greater than 21.3°C. While decay by free-living microbes also increases with rising temperatures, this was by a much smaller amount.

'Free-living microbes tend to perform poorly in dry environments, whereas termites have behavioural adaptations that allow them to do well in arid and semi-arid conditions,' Paul says. 'As it gets hotter and drier, the termites and their symbionts tend to do much better than free microbes and increase the proportion of wood decay they perform.'

The report suggests that even on a climate pathway where the world warms by less than 2⁰C, the areas with the highest termite activity will expand by around two million square kilometres. 

In a pathway with continuing high use of fossil fuels, this could increase to 2.5 million square kilometres, with the southern United States, the fringes of the Mediterranean and southeast Asia additionally becoming areas with the highest activity of wood-feeding termites.

These rising temperatures could also have an impact on the survival of termite species which prefer cooler and more moist environments.

'Most termite species like evergreen, wet forests and only wood-feeding termites will benefit from rising temperatures,' Paul says. 'The role of wood-feeding termites will increase as it gets hotter and their numbers will increase.'

'Overall, it is likely that the diversity of termites as a whole will drop but the abundance of wood-feeding termites will increase.'

Declines in these species could have knock-on effects for the other roles termites play in ecosystems, such as helping to increase the drought resistance of rainforests.

The authors of the report have called for further research to investigate how the activity of certain species of termites that cultivate fungus will be affected to add to the accuracy of their estimates.