Epsilon Archive for Student Projects

Abstract

In Northern Fennoscandia, the installation of hydropower plants has influenced the hydrological and ecological condition of almost all riverine and riparian ecosystems. River regulation can have negative effects on ecosystems through lowered species diversity, declining populations as well as densities. Bats are important indicator species in riparian ecosystems and negative impacts of hydropower on invertebrate food species for bats may be visible through changes in bat diversity, activity and population abundance. As the main bat species in this region, Northern bat Eptesicus nilssonii, heavily depends on insects. However, there is little knowledge on how river regulation by hydropower affects bat activity.
In this study, I compared the activity of E. nilssonii and other detected species across a gradient of river regulation in 31 sites widely distributed throughout northern Sweden. Bats can be easily detected using audio recorders. Specifically, the project aims to evaluate in the northern rivers:
- Occurrence and timing of bat detections, especially of E.nilssonii
- Variation of bat activity over time, regulation, and riverbank habitat parameters - habitat heterogeneity (represented through variability of slope and NDVI)
I found a strong seasonality of bat detections with a strong peak 07th to 13th August, likely due to the bright summer nights prior to that. Surprisingly, I identified bats of the genus Myotis as often as E. nilssonii, even at the northernmost locations. My results show that in this region, latitude is the strongest factor controlling bat activity, as we approach the limit of the distribution range. Through modelling I further found river regulation, represented by the amount of zero-flow hours, to be a major negative influence. I therefore attest an effect of hydropower operations on bat activity in Northern Sweden. This highlights the strength of this indicator for steering and monitoring restoration efforts. However, behavioural patterns and drivers for bat activity across the landscape need to be solidified by further research.