This year TerraLab introduced environmental DNA, or eDNA, as part of our ecological services. eDNA metabarcoding is transforming the way we approach biodiversity assessments because it allows us to rapidly obtain a detailed biological readout of a site with minimal disturbance. When organisms move through the environment they shed traces of genetic material into soil, water or sediment. By collecting and analysing these traces we can detect a wide range of species including those that are rare, cryptic, nocturnal or otherwise difficult to survey through traditional methods. This technology does not replace ecological surveys, but it does add a powerful layer of certainty and depth to them. It allows us to see beyond what can be observed in a short field visit, providing clients with a clearer understanding of the life their land supports.
The benefits of eDNA metabarcoding are increasingly recognised across research, conservation and land management. The ability to process a single water or soil sample and reveal hundreds of taxa at once is a step change from traditional approaches that often rely on repeated visits and specialist expertise. eDNA can highlight unexpected biodiversity, reveal early signs of invasive species and provide a measure of ecological condition that is rapid and cost effective. Our earlier blog on the subject discussed examples from freshwater systems where eDNA has been used to track threatened fish and amphibians, and from terrestrial systems where plant communities were revealed that might otherwise have been overlooked. It is a method that can add immense value to compliance reporting, environmental impact assessments and restoration planning.
At the same time it is important to acknowledge the limitations of the method. eDNA results are constrained by the reference databases used to identify sequences. Not all species have reference DNA available and as a result many detections can only be assigned to genus or family level rather than to a species. This can be particularly limiting for groups where local endemics have not been sequenced. Environmental factors can also affect results. Rainfall can dilute DNA or introduce material from upstream, pH and pollutants can degrade samples, and turbidity can clog filters before an adequate volume is obtained. Interpretation requires expertise, as non-specialists may assume that a detection equates to confirmed presence of a species at the site, when in reality it is better viewed as evidence of DNA within the sampled environment that requires cautious assessment. These limitations mean that eDNA is best viewed as a complementary tool, one that works alongside ecological surveys rather than replacing them.
Collecting the eDNA sample from the Powlett River.
To demonstrate how our combined approach adds value we present a recent case study at Outtrim in South Gippsland. On the 14th of August 2025 we undertook a rapid assessment of the Powlett River at this location. Rainfall in the preceding 24 hours was less than 1 mm, meaning conditions were relatively stable. The water was however turbid and our filter clogged after only 100 mL of water was processed, well short of the 1000 mL we aim for. Despite this limitation the results were highly informative. The eDNA analysis identified 295 taxa across a broad range of life forms. The breakdown is presented below.
Amoebae 1
Archaea 5
Bacteria 181
Birds 2
Bryozoans 0
Ciliates 18
Crustaceans 6
Cryptomonads 0
Diatoms 2
Dinoflagellates 0
Fish 0
Flatworms 1
Fungi 1
Green algae 2
Heterokont algae 2
Insects 5
Mammals 4
Molluscs 1
Plants 23
Rotifers 5
Roundworms 0
Spiders 1
Springtails 2
Worms 14
Other 19
The diversity represented in this table is remarkable given the small water volume filtered. As is often the case with eDNA results many terrestrial plants were only identified to the genus level. In parallel with the sample our ecologist carried out a timed 15 minute survey within a 50 metre radius of the collection point. This rapid ecological survey identified 19 taxa. They were:
Acacia dealbata (Silver Wattle)
Acacia melanoxylon (Blackwood)
Cenchrus clandestinus (Kikuyu)
Cirsium vulgare (Spear Thistle)
Colluricincla harmonica (Grey Shrike-thrush)
Cynodon dactylon (Couch)
Dactylis glomerata (Cocksfoot)
Ehrharta erecta (Panic Veldt-grass)
Eucalyptus strzeleckii (Strzelecki Gum)
Foeniculum vulgare (Fennel)
Galium aparine (Cleavers)
Gynatrix pulchella s.s. (Hemp Bush)
Hypochaeris radicata (Flatweed)
Melaleuca ericifolia (Swamp Paperbark)
Persicaria decipiens (Slender Knotweed)
Pittosporum undulatum (Sweet Pittosporum)
Platycercus eximius (Eastern Rosella)
Rorippa palustris (Marsh Yellow-cress) and
Rubus fruticosus spp. agg. (Blackberry).
Several outcomes are worth highlighting. The eDNA analysis revealed a number of cryptic or overlooked species that were not detected by the ecologist, such as Zantedeschia aethiopica (Arum lily) which is a significant environmental weed, Lemna minuta (duckweed), and Glyceria, an important native aquatic grass. At the same time the ecological survey identified a key threatened species, Eucalyptus strzeleckii, which is listed as vulnerable under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). In the eDNA results this was only resolved to Eucalyptus spp. This difference underscores why our service matters. eDNA provides an extraordinary breadth of detections but ecological expertise is essential to resolve fine scale identifications and to ground truth the results. Together, the methods produce a more reliable and useful outcome for clients.
It is also worth noting that only one of the 19 taxa identified by the ecologist appeared in the eDNA results. This discrepancy may reflect the low water volume filtered, the incomplete nature of the reference database, the timing of the survey and the fact that many detections could not be identified beyond genus level. When both methods are combined the total number of taxa identified at the site rises to 314. That represents a far more complete picture of biodiversity than either method could achieve on its own. For the client it means greater confidence that important species are being captured in assessments.
The conclusion from the Outtrim case study is clear. eDNA is a powerful and rapid tool for biodiversity assessment. Ecological surveys remain slower but provide context and resolution that eDNA cannot yet fully achieve. By combining the two we are able to offer a comprehensive workflow that captures the best of both approaches. At TerraLab we package these services together into an affordable product that gives land managers, local governments and private organisations access to high quality biodiversity information. Whether the goal is to detect threatened species, confirm the presence of invasive plants or simply understand what lives on a property, our integrated eDNA and ecological survey service delivers results that are objective, reliable and transparent.
Our eDNA results for this assessment are public, and can be viewed here.