November 2019 | Volume 21 No. 1
Termites’ Role in Sorting out Droughts
The findings are the result of collaborative research, co-headed by Dr Louise Ashton of HKU’s School of Biological Sciences, and research teams led by Dr Kate Parr from the University of Liverpool and Dr Paul Eggleton from the Natural History Museum in London. The results were reported as the cover story of Science magazine.
“Our termite study was part of a large, multidisciplinary project, involving multiple institutions called the Biodiversity and Land-Use Impacts (BALI) project,” said Dr Ashton, who worked on the project with another post-doctorate Dr Hannah Griffiths. “The study involved understanding the role of both termites and ants in ecosystem processes.”
For the research, the team carried out a large-scale manipulation in the rainforests of Borneo where they suppressed the activity of termites. By comparing the termite-suppression plots with control plots, they could quantify the role of termites in processes such as decomposition, maintaining soil moisture and soil nutrients and see if there were any knock-on effects in other parts of the ecosystem, such as in plant survival.
Dr Hannah Griffiths and research assistants Mirah, Ele and Kidus collecting leaf litter from the rainforest floor. The sampling is to look at invertebrates that live in the leaf litter.
El Niño conditions
By what she describes as ‘serendipitous chance’, a large El Niño drought occurred at the same time the experiment began in 2015. They were lucky to have a good team and enough funding to continue the experiment for a two-year period, throughout the drought and also in non-drought conditions. Thus they were able not only to investigate the roles of termites in tropical rainforests, but also how drought influences termite activity and the knock-on effects on the ecosystem.
“We found that during the drought, termite numbers doubled, and in the presence of termites, there was higher soil moisture, soil nutrient heterogeneity and decomposition,” said Dr Ashton. “Most surprisingly, seedlings on plots with termites were better able to survive the drought period. These results show that termites can buffer some of the effects of a drought.”
The results were possible because they carried out a large-scale field manipulation of biodiversity. Working in the tropical rainforests of the Maliau Basin Conservation Area of Malaysian Borneo, they were able to set up four 80 x 80-metre termite-suppression plots and four control plots. They collaborated too with a team of Malaysian research assistants to carry out regular field expeditions, which were around three months long. Over the course of the whole project they spent around nine months in the field.
“This type and scale of project is quite rare, because it is difficult to alter the diversity in rainforests, which are very stochastic systems,” said Dr Ashton. “Additionally, insects, particularly termites, are understudied, especially in terms of their ecosystem processes and in the tropics.”
Until this study, what was known about termites was that they are abundant in tropical ecosystems and one of only a few living creatures capable of breaking down the cellulose found in plant material. They create temporary protective structures, known as ‘sheeting’, above the ground, which enable them to move through the forest even during drought conditions. They also play an important role in soil processes such as decomposition and soil moisture, but their exact roles have never been fully quantified in real-world experiments – partly because it is difficult to suppress termite activity.
To find out more, the research team developed innovative suppression techniques using toilet paper rolls. “Termites really like eating toilet paper because it is easy to digest,” said Dr Ashton. “We treated the toilet paper rolls with some termite insecticide, which enabled us to suppress the termites on our plots. By comparing these plots with control plots with termites present, we were able to determine the roles of termites in ecosystems.”
The implications of the research are hugely important because droughts are predicted to become more frequent and more severe in the tropics in coming years and this study shows how crucial biodiversity is for mitigating their devastating effects.
The research team developed novel suppression techniques using toilet paper rolls. Over 4,000 toilet paper rolls were used in the study.
Now, the team is looking beyond Borneo to see if results are the same elsewhere. “Some of the team are already carrying out similar large-scale manipulation experiments in South African savannahs,” said Dr Ashton. “It will be very interesting to see if termites are also important in other ecosystems.”
They are also further diversifying the focus of study. “As most tropical landscapes are now mosaics of different land uses, I’m also hoping to be able to work on understanding the role of insects in disturbed forests and agricultural systems,” she added.
“Our results indicate that termites are important for maintaining healthy rainforests during periods of stress. As ecosystems are under increasing multiple pressures such as land-use change and climate change, understanding and maintaining biodiversity is becoming increasingly important.”
The research in Borneo was Dr Ashton’s second post-doctoral study, the first being in the Australian tropical rainforest in 2013 and 2014. Tropical field ecology is one of her main areas of interest and her PhD involved using insects as tools to understand ecological patterns and climate change. She concluded by expressing her gratitude to all involved on the BALI project: “This study was a really large team effort and was only possible through collaboration.”
Researchers in the forest – (from left) Dr Louise Ashton, Dr Hannah Griffiths, Dr Kate Parr and Dr Amy Zanne.
Insects, particularly termites, are understudied, especially in terms of their ecosystem processes and in the tropics.
DR LOUISE ASHTON