Termites like heat, which risks aggravating global warming

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Termites love heat, which may worsen global warming

Close-up of an Asian subterranean termite (Coptotermes gestroi).

Termites' appetite for wood increases with rising temperatures, which which risks releasing more carbon into the atmosphere and contributing to global warming.

For example, a large international study conducted in 22 countries shows that the ability of termites to decompose wood is nearly seven times faster per 10°C increase in temperature.

Termites are often considered a nuisance because they feed on cellulose – one of the main components of plants such as the wood used to frame houses.

An Asian subterranean termite (Coptotermes gestroi) soldier in a cardboard nest.

They are often considered harmful insects, but termites that attack human constructions represent less than 4% of all species in the world, notes the biologist Maria Juliana Pardo who participated in the study under the supervision of professor Jim Dalling of the University of Illinois, also associated with the Smithsonian Tropical Research Institute (STRI).

“In In fact, most species of termites play an essential role in natural ecosystems, particularly in the tropics, as they help to recycle the dead wood that covers the forest floor.

—Maria Juliana Pardo

Without those insects – and the microbes (bacteria and fungi) – that turn plant waste and animal carcasses into humus or minerals, the Earth would be filled with dead organisms.

Although microbes and termites all break down dead wood, there are important differences between them. While microbes need water to grow and consume wood, termites can function at relatively low humidity levels.

  • Growing trees play a central role in the global carbon cycle, as they absorb carbon dioxide from the atmosphere through photosynthesis. Once they die, however, they become a source of carbon emissions.
  • Dead wood is an important carbon store. The size of this reservoir is partially determined by the decomposition of wood by living organisms such as microbes and termites.
  • To date, several studies have shown the role of microbes in wood decomposition, but few have focused on the role of termites in this process.

To successfully To assess the rates of consumption of dead wood by termites and microbes in different climates, about 100 biologists led by Amy Zanne of the University of Miami have launched a vast international initiative.

Biologist Amy Zanne (left) and students from Campinas State University near termite mounds in a tropical savannah in Brazil's Chapada dos Veadeiros National Park .

For a period of up to 2 years, we followed the decomposition of blocks of pine wood (Pinus radiata) in 133 sites that spanned ecosystems on six continents, explains Maria Juliana Pardo, who studied at the University of Montreal.

These wooden blocks were covered with wire netting the ground surface.

The experimental device was the same on all sites: wooden blocks covered mesh on the floor surface.

The experimental design was the same at all sites, i.e. 20 stations of pairs of wooden blocks spaced at least 5 meters apart.

“Half of the blocks had small holes in the wire mesh, allowing termites to gain access to them. The other half had no holes, so only microbes could access the blocks through the mesh.

—Maria Juliana Pardo

This experiment assessed how the rates of wood consumption by termites and microbes varied with climatic factors, such as temperature and precipitation, adds the biologist.

Degradation of a block of wood accessible to termites in the tropical forest of the island of Barro Colorado in Panama.

Result: Researchers found that the blocks covered by the net with holes decayed faster than those without, showing the importance of the contribution of termites to decomposition.

Experience has also shown that termites are extremely sensitive to temperature and that their activity increases considerably in hotter and drier climates .

Even better, the study was able to quantify for the first time how heat-loving termites are.

Termites from a region where the temperature is 30℃ eat wood almost seven times faster than in a place where the temperature is 20℃, explains Maria Juliana Pardo.

“In comparison, microbial (bacteria and fungi) decomposition of wood only doubles with the same increase in temperature (10℃). »

— Maria Juliana Pardo

Experiment has also shown that if rainfall does not affect the phase of wood decomposition by termites, it makes insects less efficient to find wooden blocks.

“The finding [of wooden blocks] by termites was higher in hot, dry places like savannahs, seasonal rainforests, and subtropical deserts.

— Maria Juliana Pardo

This study, combined with various projections of climate change, suggests bright days for termites on Earth in the coming decades.

Warming will lead to a greater territorial distribution of termites outside the tropics, north and south of the equator, continues the researcher.

“These results are important because they give us insight into the role of termites in the process of wood decomposition and in the global carbon cycle, which has so far been largely overlooked.

—Maria Juliana Pardo

If termites become more productive in breaking down dead wood due to warming, they will allow it to be removed more quickly, resulting in more carbon being released into the atmosphere.

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So reducing the amount of carbon stored on Earth could trigger a feedback loop that would accelerate the rate of climate change.

The study published in the journal Science shows how essential it is to understand the dynamics of the communities of organisms that decompose dead wood, because it can help to predict the role of carbon buried in terrestrial ecosystems on the effects of climate change.

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