The deforestation of New Zealand resulted in dramatic biological shifts in freshwater ecosystems, a University of Otago study has found.
Published in Science of the Total Environment, the study used more than 100 freshwater environmental DNA (eDNA) samples from across Otago and Southland to compare the biodiversity between forested and deforested streams.
Focusing on about 100 species of ecologically important freshwater insects, such as mayflies and stoneflies, the Department of Zoology researchers found a distinct insect group linked to forest loss.
Lead author Professor Jon Waters was surprised by how substantially and predictably the forested and deforested eDNA samples differed.
“We could easily tell whether a stream was forested or deforested just from looking at the insect eDNA data.
“Deforestation clearly has had major impacts on the diversity of species present in our rivers, and also on ecosystem function, with several key forest species now being rare or absent in deforested regions,” he said.
The study is important as freshwater quality and biodiversity are significant environmental issues, both in NZ and overseas.
“New Zealand was fully forested before humans arrived just a few centuries ago. With only a quarter of the original cover left, the associated environmental impacts have been severe, and degradation of our waterways has been widespread.
“One major concern relates to the loss of wetland vegetation cover and its potential effects on freshwater ecosystem health.”
As efforts turn to mitigating these impacts and restoring freshwater ecosystems, Waters said, eDNA represents a key tool for efficiently and rapidly monitoring ecosystem-wide health, and for testing the success of restoration efforts.
He said that “eDNA is important for detecting the presence of organisms within particular regions, with a famous example being the detection of viruses in wastewater”.
“In the same way, we are now using eDNA to assess the diversity of species within our ecosystems, for instance, to compare the species found in natural versus degraded waterways.”