How COWI powers wind farm bat monitoring across Denmark with BioSonic

COWI is a leading Scandinavian engineering consultancy with a dedicated ecology division. Their bat monitoring work on wind farm projects across Denmark requires accurate species identification at scale, with multiple team members collaborating on the same datasets. BioSonic provides the classification accuracy and team workspace that this kind of work demands.

About COWI

COWI is a major international engineering, environmental, and economics consultancy headquartered in Denmark. The company employs thousands of specialists across Northern Europe, with a strong ecology team that handles biodiversity assessments for infrastructure projects. Their bat work is concentrated on wind energy development, where European regulations require detailed species-level monitoring both before and after turbine installation.

Wind farm bat monitoring generates large, continuous datasets. Detectors are deployed at nacelle height and ground level across multiple turbine locations, often running for months at a time. The resulting audio data can be enormous, and every recording needs to be classified to species level to satisfy regulatory requirements and inform curtailment decisions.

The challenge

Wind farm bat monitoring presents specific challenges that distinguish it from standard ecological survey work:

• Volume. Months of continuous recording across multiple detector positions generates far more data than a typical survey project. Manual review of every call is not feasible.
• Accuracy requirements. Curtailment recommendations depend on which species are present. Misidentifying a common pipistrelle as a Nathusius' pipistrelle, or missing a Barbastella entirely, has direct consequences for turbine operation schedules and regulatory compliance.
• Noise filtering. Nacelle-height recordings contain substantial wind and mechanical noise. A classifier that cannot reliably separate bat calls from non-bat noise creates a flood of false positives that analysts must then review by hand.
• Team collaboration. Multiple biologists often work on the same wind farm project. They need to access the same data, review each other's work, and produce consistent outputs without version-control problems.

These requirements meant COWI needed a platform that combined high classification accuracy, strong noise rejection, and a collaborative workspace.

Why BioSonic

Peter Sivertsen, a biologist at COWI, summarised what sets BioSonic apart from the alternatives the team had evaluated.

Two capabilities were decisive. First, BioSonic's species identification accuracy meant the team could trust the automated output on the vast majority of calls, reserving manual review for genuinely ambiguous cases rather than correcting systematic errors. Second, the noise filtering — the ability to distinguish bat echolocation from wind, rain, and mechanical sounds — dramatically reduced the volume of false positives that would otherwise consume analyst time.

The cloud-based platform also addressed the collaboration challenge. Multiple biologists can work on the same wind farm project simultaneously, reviewing classifications, adding notes, and generating reports from a shared workspace. This eliminated the file-passing and duplication that had slowed previous projects.

The result

COWI has adopted BioSonic for their wind farm bat monitoring work across Denmark. The platform handles the scale of continuous monitoring datasets while maintaining the classification accuracy that regulatory reporting demands. The team spends less time on manual review and noise filtering, and more time on the ecological analysis and curtailment recommendations that their clients and regulators need.