Abstract
Global expansion of marine renewable energy (MRE) technologies is needed to help address the effects of climate change [1], to ensure a sustainable transition from carbon-based energy sources, and to meet energy security needs using locally generated electricity. Although the amount of potentially harvestable tidal stream and wave energy from nearshore regions around the world is sufficient to meet current global electricity demand [2], the share of MRE in global electricity generation remains low at approximately 1 TWh yr-1; falling well short of its potential and is due to the relatively small scale of device deployments to date (i.e., single devices and small demonstration-scale arrays). Expansion of MRE to largescale commercial arrays (hereafter ‘arrays’) is needed to meaningfully address the effects of climate change, safeguard energy system transition, and provide energy security [3].
Several obstacles impede MRE expansion, including difficulties in obtaining regulatory approvals due to uncertainty around environmental effects resulting from a paucity of post-installation environmental monitoring data that confounds our ability to differentiate between unknown and realized effects of MRE development for marine ecosystems [4]. A long-established framework for assessing the effects of MRE development focuses on understanding ‘stressor-receptor interactions’ [5] (hereafter ‘stressors’); seven of which have been identified as key concerns post-installation:
- Collision risk
- Underwater noise
- Electromagnetic fields
- Changes to habitats
- Displacement
- Risk of entanglement
- Changes in oceanographic systems
Our understanding of effects for these stressors continues to improve for single MRE devices, but remaining uncertainties complicate the task of predicting how marine ecosystems and their constituents will be impacted by arrays. Effects are unlikely to scale linearly with the number of devices, but are probably complex and nuanced, site specific, dependent on array configuration, cumulative (in some form), and have the potential for nonlinear environmental responses. Establishing generalized concepts for how effects may ‘scale up’ provides a useful foundation for developing and testing hypotheses to improve our understanding of the potential environmental risks of MRE expansion. This paper establishes generalized concepts for these seven key stressors so that a robust scientific approach can be taken to improve our understanding of effects for arrays; information that is needed to facilitate the deployment of MRE technologies at scales that can make meaningful contributions in addressing the effects of climate change, assisting energy system transition, and ensuring energy security.