APEM Group Enhances Digital Aerial Survey Data Precision with IMU Technology
Over the past year, APEM Ltd, part of APEM Group, has refined its digital aerial survey (DAS) methodology to deliver...
As Australia’s offshore wind sector gains momentum, developers are navigating a complex landscape of environmental regulations, stakeholder expectations, and ecological sensitivities. With a growing offshore wind project pipeline and increasing investment in renewable energy projects, the need for robust environmental data and early-stage planning has never been more critical.
Recently, APEM Group, industry leaders and marine science experts came together to explore one of the most pressing challenges in offshore wind farm development: understanding marine mammal survey data for project approvals. The discussion underscored the importance of strategic data collection, regulatory alignment, and cross-sector collaboration to ensure offshore wind projects are both environmentally responsible and commercially viable.
The regulatory landscape: A high bar for environmental protection
Australia’s offshore wind developers are required to operate within a stringent regulatory framework, primarily governed by the Environment Protection and Biodiversity Conservation (EPBC) Act. Raquel Carter, Head of Environment at Energise Renewables and former Chief Environmental Scientist at NOPSEMA, explained, the EPBC Act requires that any action that will have, or is likely to have a significant impact on a Matter of National Environmental Significance (MNES) – such as listed threatened species, listed migratory species, or the Commonwealth marine area – must be referred to the Environment Minister.
This framework and associated guidance place a strong emphasis on:
- Protection of Matters of National Environmental Significance (MNES), including World Heritage areas, National Heritage places, internationally important Ramsar wetlands, threatened species and ecological communities, migratory species, Commonwealth marine areas, Great Barrier Reef Marine Park, Nuclear actions (e.g., uranium mining), and water resources affected by large coal or gas developments.
- Environmental Impact Assessment (EIA) of proposed actions that may significantly affect protected matters requires the application of the mitigation hierarchy, a robust demonstration that impacts on MNES will be acceptable and offsets for significant residual impacts on MNES.
- The principles of ecological sustainable development including the conservation of biodiversity, intergenerational equity and the precautionary principle.
- Protection of indigenous heritage and knowledge, including promoting partnering with First Nations people to seek First Nations knowledge of country and environmental management, protecting and managing the environment and conserving and using Australia’s biodiversity in a sustainable way.
Importantly, the EPBC Act mandates that decisions must not be inconsistent with recovery plans. For offshore wind developers, this means demonstrating that their projects will not impact threatened species that would impede species recovery, such as preventing biologically important behaviours from continuing. This applies to the blue whale and southern right whale (both of which have statutory recovery plans in place).
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A person must not take an action that will have or is likely to have a significant impact without approval from the Minister of Environment. That’s why referrals are largely going to be needed for most, if not all, offshore wind farm developments in Australia.
Raquel Carter, Head of Environment at Energise Renewables
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Survey Toolbox: Integrating methods for robust impact assessments
Understanding the distribution, abundance, and behaviour of marine mammal species is essential for undertaking robust EIA’s. Dr. Ross Culloch, APEM Group’s Head of Marine Mammals, emphasised, “There’s no one-size-fits-all approach. The key is to design surveys that are fit for purpose and aligned with regulatory expectations.”
To understand these factors, APEM Group and its partners advocate a toolbox approach, integrating multiple survey methods to build a comprehensive ecological baseline for marine mammals, alongside other receptor groups, such as seabirds.
Digital aerial surveys
Digital aerial surveys are a non-invasive, high-resolution method for detecting marine mammals, seabirds, and vessels across vast ocean areas. Dr. Ali Cotton, Associate Director in APEM Group’s Marine Wildlife Survey team, explained, “These surveys are particularly effective for capturing natural seasonal and interannual variability, which is critical for understanding species distribution and behaviour over time.”
One of the key advantages of digital aerial surveys is their ability to collect multiple types of ecological data simultaneously. Using a system of vertically oriented high-resolution cameras, the surveys can detect not only animals at the surface but also those just below, thanks to the clarity and depth penetration of the imagery. This allows for efficient data collection on marine megafauna, birds, and human activity, such as vessel presence, all in a single flight.
Survey design is never one-size-fits-all. Each survey needs to be tailored to the specific ecological and regulatory questions at hand. For example, survey coverage might be increased during key migration periods, and buffer zones around project sites are carefully considered to assess potential displacement effects. The use of grid-based designs, as opposed to transects, is often preferred for site-specific studies due to their statistical robustness and even spatial sampling.
While digital aerial surveys are highly effective, they are not without limitations. They are weather-dependent and may miss deep-diving species that spend extended periods underwater. However, when integrated with other methods, such as passive acoustic monitoring or biologging, they form a powerful part of a multi-method “toolbox” approach to marine mammal assessment.
Visual aerial surveys
Visual aerial surveys offer a complementary approach to digital methods, providing real-time observations of marine mammals by trained observers aboard aircraft. Dr. Ali Cotton explained, “These surveys are particularly valuable for capturing behavioural data and species identification, especially during key periods such as migration seasons.”
Unlike digital surveys, which rely on post-flight image analysis, visual surveys allow observers to record sightings and behaviours as they happen. This immediacy enables the collection of nuanced data on surfacing patterns, group dynamics, and potential responses to environmental stimuli. The wider field of view from the aircraft also allows for broader spatial coverage, which can be advantageous when surveying large or remote areas. However, unlike digital aerial surveys, the detection bias needs to be accounted for (i.e. an observer’s ability to detect animals reduces over distance from the transect).
Limitations of visual aerial surveys include observer fatigue, weather dependency, and the lower altitude of flights introduce safety considerations and potential biases. Additionally, the accuracy of species identification depends heavily on the experience of the observers, and correction factors must still be applied to account for submerged animals.
Visual aerial surveys remain a cost-effective and repeatable method for gathering targeted data on marine mammals. When integrated with digital surveys and other techniques, they contribute valuable behavioural and contextual insights that strengthen the overall environmental assessment.
Vessel-based surveys
Vessel-based surveys are a widely used and valuable method for collecting marine mammal data, particularly when integrated into broader offshore operations. Dr. Jonathan Botha from Biosis, part of APEM Group, explained, “One of the key advantages of this approach is its flexibility and cost-effectiveness, especially when marine mammal observers (MMOs) are deployed on vessels already conducting other surveys, such as seabird or habitat assessments.”
These surveys typically involve trained observers conducting distance sampling along predefined transects, allowing for the estimation of species abundance and density. Observers also record behavioural data using standardised ethograms, which can provide insights into how marine mammals interact with their environment and respond to human activity. Just like visual aerial surveys, detection bias needs to be accounted for (i.e. an observer’s ability to detect animals reduces over distance from the transect). In addition, animals below the surface need to be accounted for using correction factors.
Other considerations include vessel noise, which can deter some species while attracting others; this is important to consider when interpreting these data. Surveys are also constrained by weather and sea state, and while the slower speed of these surveys increases the likelihood of recording deeper diving species (which spend less time at the surface), the spatial coverage is considerably reduced, as compared to aerial methods.
When used alongside aerial surveys, passive acoustic monitoring, and biologging, they contribute to a more comprehensive understanding of species presence and behaviour, which helps inform the assessment of potential impacts to marine mammals from offshore wind activities.
Biologging
Biologging offers a powerful way to collect fine-scale data on marine mammal behaviour, particularly for species like Australian and New Zealand fur seals that forage locally and may interact with offshore wind infrastructure. Biologging has been especially valuable for understanding the movements and habitat use of lactating female seals, which represent a significant portion of the population and frequently return to breeding colonies. However, Dr. Jonathan Botha highlighted that this brings key knowledge gaps relevant to pre-existing data, for example, we do not know as much about the behaviour of adult male fur seals, non-breeding individuals and juveniles as these are rarely studied in this manner.
These studies involve attaching tracking devices to individuals and, in the case of seals, this requires using approved capture and sedation techniques, where necessary. The devices can collect fine-scale spatial, behavioural, and environmental data over extended periods, offering insights into time spent at sea and on colonies, which is difficult to obtain through other methods. These studies are also undertaken on cetaceans, such as the blue and southern right whale, typically using non-invasive tagging methods, such as suction cups, which attach directly to the skin of the animal and fall off over time and can be recovered by the researchers. The data obtained from biologging includes dive profiles, foraging patterns, and habitat preferences, all of which are critical information for understanding how individuals and populations are using their habitat.
However, biologging requires highly skilled personnel, significant field time, and strict adherence to animal ethics and permitting requirements. For example, access to breeding colonies can be logistically complex, with ethical considerations regarding potential impacts on mother–pup behaviour. The cost of equipment and deployment is high, and sample sizes are typically low (i.e. few animals tagged relevant to the population size).
As Dr. Jonathan Botha noted, colony-based biologging is likely best suited for regional-scale assessments with a focus on collaborative and strategic research efforts rather than dedicated site-specific surveys. However, with advancements in biologging technology (including cost reduction), as well as newly developed capture and sedation techniques, accessing larger numbers of non-breeding animals at haul-out sites may be a viable option. This could hold value at the project-level scale and would be worth consideration for those projects located close to known haul-out sites.
Passive Acoustic Monitoring (PAM)
Passive Acoustic Monitoring (PAM) is commonly used for detecting vocalising marine mammals. As Lorenzo Scala, Senior Marine Scientist at Seiche Ltd., highlighted, “PAM enables continuous, autonomous data collection that complements visual and aerial survey methods, especially in offshore areas where baseline data are sparse.”
Static PAM systems are typically used for baseline site characterisation and monitoring and consist of seabed-deployed acoustic recorders with hydrophones that record underwater sounds, including whale songs, dolphin clicks, and other biologically relevant signals. These systems can operate for months at a time, capturing seasonal and diel patterns in species presence and, in some cases, behaviour. PAM is effective for detecting deep-diving species that may be missed during digital or visual surveys.
Lorenzo Scala emphasised the importance of designing PAM arrays with redundancy to mitigate risks such as equipment failure or data loss. He also noted the need for coordination and communication with other sea users, particularly fisheries, to avoid conflicts and ensure successful deployments and recovery.
“There’s always the risk of equipment failure or data loss,” Lorenzo Scala explained. “It’s crucial to build redundancy into your study design and maintain strong communication with other sea users, especially fisheries.”
PAM data can be analysed using a range of tools, from manual review to automated classifiers, which can identify species groups and acoustic populations from their stereotyped calls, distinctive clicks and whistles. Of course, there are limitations to this approach; for example, animals have to be vocalising to be detected. Nonetheless, PAM is arguably one of the more important tools in the toolbox for understanding spatial and temporal patterns of marine mammal presence and for informing and successfully undertaking mitigation protocols during the construction phase.
Designing for success: A stepwise approach
APEM Group recommends a stepwise framework for designing fit-for-purpose surveys:
- Desk-based review: Identifying priority species and critical knowledge gaps, aligned with regulatory requirements and relevant best practice and guidance.
- Survey design: Identifying primary and supplementary methods tailored to project needs, considering economies relating to data collection methods focused on other receptor groups.
- Stakeholder engagement: Engaging with key stakeholders such as regulators, scientists, and Indigenous communities at the earliest opportunity.
- Data Integration: Combining datasets to reduce uncertainty and support robust impact assessments.
- Adaptive management: Thinking across all stages of the project from the beginning will help in preparing and planning for post-approval monitoring and mitigation.
This approach ensures that offshore wind feasibility studies and environmental assessments are grounded in science, aligned with policy, and responsive to stakeholder concerns.
At APEM Group, we believe that early, strategic engagement is the key to unlocking the full offshore wind potential of Australia. If developers, consultants, regulators, and communities work together, we can build a renewable energy future that is both sustainable and scientifically sound.
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