In our latest QAEco reading group, Emily McColl-Gausden and Reid Tingley led a discussion on ‘Environmental DNA for wildlife biology and biodiversity monitoring’ by Kristine Bohmann, Alice Evans and colleagues.
Bohmann et al. examined eDNA from a monitoring/ecology perspective, and therefore didn’t delve too deeply into the genetic details (which some of our less genetically-inclined members appreciated!). The paper did, however, highlight some very interesting, and perhaps less well-known eDNA applications from both aquatic and terrestrial environments. Surveying for endangered deer using leech blood and collecting eDNA from Arctic fox paw prints were two intriguing examples. Bohmann et al. also highlighted some important limitations of eDNA sampling, such as the occurrence of false positive detections both in the field and in the lab. The paper looked to the future in its longer term aspirations for eDNA, in addition to more realistic shorter-term goals.
We all agreed that there were many potential applications of eDNA sampling, and that researchers were only beginning to tap into its potential. There are also certainly benefits from an animal ethics point of view. However, one issue that caused much discussion was the ability to estimate abundance from eDNA. Some members of the group were rather dubious about the strength of this correlation, and how it might change in different environments. We came to the conclusion that eDNA-based abundance data could potentially be used as an index to rank the abundance of species, rather than an absolute number (e.g., for differentiating rare vs. common species).
For some in the group, the paper was too optimistic in its predictions of global networks of eDNA monitoring stations. Others, however, thought that technological advances could enable widespread data collection in the not-too-distant future. Handheld devices for sampling and analysing eDNA data were mentioned as an example of such an advance.
More broadly, this paper catalysed an interesting discussion regarding how intensely we scrutinise new technologies in ecology. The point was raised that we don’t seem to question the more established sampling techniques as much as we probably should. For example, electrofishing is not 100% effective for detecting fish, yet imperfect detection is rarely discussed or considered. And, of course, as a group of quantitative ecologists who are interested in conservation decision-making, we wondered about the value of resolving many of the uncertainties regarding eDNA sampling. Given a fixed budget, should we invest in resolving such uncertainties, or are we better off taking additional environmental samples? Following on from that point, we agreed that we would like to see more papers on the cost-effectiveness of eDNA sampling, as well as more focus on imperfect detection. Did we mention that we’re quantitative ecologists?