- Scientists have used a combination of drone technology and environmental DNA analysis to detect animals that live in the rainforest canopy in the Peruvian Amazon.
- Using the technology, researchers were able to draw a contrast between species detected from canopy samples and water samples.
- They found that water samples indicated the presence of more species, while canopy samples detected taxonomic groups not found in water samples, highlighting the need to use both methods complementarily.
What’s lurking in and around the rainforest canopy?
That’s a hard question to answer, especially in tall and dense forests. Traditional tracking methods, like camera traps, often miss out on elusive species that live high in the canopies. Acoustic monitoring might help detect some species, but not the relatively quiet ones.
Scientists are now using a combination of drone technology and environmental DNA (eDNA) analysis to unravel the mysteries unfolding in the treetops.
A team at the Environmental Robotics Lab at ETH Zürich collaborated with nonprofit organization Wilderness International to deploy drones to collect eDNA samples from rainforest canopies in Peru.
Environmental DNA is the genetic material left behind in the environment by animals via their hair, fur or saliva. These flow into water or float around in the air before settling on leaves, branches and canopies. For a long time, scientists have focused on extracting genetic material from water samples to detect the animals living in a forest or ecosystem. However, this often left out arboreal, or tree-dwelling, species.
“We have researchers who cover the ground level when it comes to traditional biodiversity research,” Marie Schreiber, head of science communication at Wilderness International, told Mongabay in a video interview. “But what is going on in the treetops is very difficult to understand and assess.”
It was to fill this data gap that the two organizations collaborated to pilot the technology in two protected areas north and south of the Tambopata River in Peru. Identifying and protecting the biodiversity in these locations is especially crucial in the face of rising deforestation for agriculture, road construction and gold mining. “A lot of [the area’s biodiversity] has not really been discovered or studied a lot,” Schreiber said. “Because although there is high variation in species numbers, the actual numbers of individuals per species is very low.”
The team first decided on the location in each forest along with a predefined flight path for the drone. They then flew the drone to those locations and lowered a probe, equipped with a moist cloth pad, into the vegetation. The probe moves up and down, rubbing against trees and branches, with the pad making it easier for DNA material to stick to it. During later flights, the team was able to automate the process by entering the location into the system. “We want to maximize the amount that we collect within a given flight,” Steffen Kirchgeorg, a postdoctoral robotics researcher at ETH Zürich who developed the system, told Mongabay in a video interview. “We wanted to increase the amount of contact because we know that eDNA is rather stochastic” or randomly distributed — “and is not super homogeneous.”
On analyzing the samples, the team was able to detect 257 vertebrate species, with one sample in particular found to contain genetic material from as many as 50 different species. “It also matches with our traditional ground data” of the species present in the area, Schreiber said. “For us, that was important in order to understand the reliability of the data.”
They also collected and analyzed water samples. On comparing the results from the canopy samples and water samples, the team found very little overlap in detections. That suggested that canopy sampling targeted different taxonomic groups from the ones detected in water sampling. This, Kirchgeorg said, underscored the need for a distinct technique to study species living in the canopy.
They also concluded that while water samples gave higher species detection, canopy samples gathered DNA from taxonomic groups not found in water. Schreiber and Kirchgeorg said this highlighted the importance of both techniques and the need to use them in a complementary manner. “This is data with a lot of impact because it helps in justifying the establishing of new conservation areas and getting funding for them,” Schreiber said.
Kirchgeorg said the cost of the technology, coupled with logistical hurdles, could serve as potential challenges in scaling it up. But he expressed hope that the potential of the technology and the rich data it provided will serve as an incentive to use it.
“The political or general safety situation may not allow us to bring in drones for these kinds of purposes,” he said. “But as eDNA analysis becomes more readily available and cheaper, this will actually really become more feasible.”
Banner image: A flowering rainforest tree in the Amazon. Image by Rhett A. Butler.
Abhishyant Kidangoor is a staff writer at Mongabay. Find him on 𝕏 @AbhishyantPK.
At the ‘Biodiversity Olympics,’ scientists work to democratize rainforest tech
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