These small insects are brilliant at preventing flooding and erosion. Let’s help them do their work.
The destruction of tropical forests changes how water, such as rain, groundwater, and rivers, moves through the landscape. Soils are less capable of soaking up incoming rainfall, often leading to flooding and erosion. However, we may get help from a most unexpected ally: the mighty dung beetle.
As a tropical forest ecologist and passionate dung beetle advocate, I look into the role of these insects in how water flows through the soils in the jungles of Sabah, Malaysian Borneo. Dung beetles dig tunnels. We believe that by doing so, they facilitate water entering the grounds.
We tested this hypothesis in a research project, gathering members from ETH Zurich, University of Zurich, Nanyang Technological University (Singapore), and University Malaysia Sabah (Malaysia). We designed a creative and novel experiment: collecting live dung beetles, feeding them controlled cow dung, measuring their impact on infiltration rates, and colouring the affected soil blue.
It isn’t the first time humans have appreciated how useful dung beetles can be. The ancient Egyptians worshipped these scarabs, seeing in them something special. Indeed, studies have shown that dung beetles are crucial drivers for many processes that occur in forests. As the name suggests, dung beetles live off faeces. They are, literally, full of shit. They also form dung balls to lay eggs in, which they then bury in underground tunnels that they dig.
By creating these tunnels, not only do dung beetles plough the soil, but also bring in fertiliser since dung is rich in nutrients. Of course, they also ensure that our world is not covered in poop! Considering their benefits, it’s only fair to assign them the degree of “environmental engineers,” as they are regularly referred to in scientific literature.
Borneo, the site of our experiment, is home to some of the most biodiverse forests worldwide. It has also been the home of Bruno Manser, the Swiss environmentalist and activist who fought for the rights of indigenous communities and the protection of these jungles in the 1980s. Yet, conversion to agriculture (e.g., palm oil) and logging have since decimated much of these forests.
Such destruction affects water-soil-plant relationships. There is an increased risk of flooding and soil erosion along with a lack of water availability to plants. Rain cannot permeate and restore groundwater because heavy logging machinery compact soils. In other terms, soil pores are squeezed shut. There aren’t many avenues left for the water to get in.
In our study, we observed that water infiltrates the soil five times more efficiently in the presence of dung beetles and reaches greater depths. Infiltration rates change, but only after a few days of dung beetle activity. This temporal lag reflects the expansion of the tunnel network.
The results are based on an experiment we conducted deep in a previously logged tropical rainforest in Sabah. We first collected live dung beetles. We then sorted them into communities, each with the same number of individuals of the same species. This step is essential to ensure comparability.
Then, we placed the insects together with cow dung in outdoor cages. That way, we could ensure that no dung beetles could escape and no additional beetles could join the dung party. We conducted this experiment with and without dung beetles to identify their effect. We also repeated these measurements in multiple cages to rule out the effect of potential differences in soils.
After placing the dung beetles in the cage for a certain time, we returned and measured how quickly water entered the soil. We used a blue dye to colour the infiltrating water. Then, we dug a vertical hole into the ground to inspect the blue pattern our little artists had created. This pattern reflects the infiltration pathways. It gives information on infiltration depth and soil pore sizes.
We have shown that dung beetles are excellent nature-based solutions to restore tropical soils of secondary forests in Southeast Asia. They are ubiquitous and abundant. One might even be rolling in your garden right now. All that is needed to attract them is mammals producing dung. As such, they stand out compared to other animals digging soil tunnels, such as earthworms and termites.
Dung beetles do not only fare well compared to other animal-based solutions: they might well be more efficient than humans. Indeed, mechanical and other engineered ways to reduce soil compaction can lead to unintended consequences such as tilling, which releases carbon stored in the soil. These artificial methods are also more costly.
We must explore the full engineering potential of dung beetles. For instance, palm oil plantations are prominent agricultural systems throughout Southeast Asia, known for their compacted soils. What if farmers could keep livestock on their farm, producing oil and meat – and dung? It would attract beetles and improve soil conditions.
However, as always, things are not that simple: livestock can also cause compaction through their hooves, having the opposite effect from what we desire. Accurate and definite answers can only be discovered through actual measurements in the field.
Most importantly, our study shows we do not always need over-engineered solutions and plain technology to restore ecosystems. We should not underestimate the influence of small creatures – after all, no one is too small to make a difference.
