"It is well established that if we want to maintain our Earth system processes in a way that suits our present societies and cultures, we collectively need to reduce greenhouse gas emissions. The impacts of not doing so will be immense and well in excess of the cost of re-tooling for a low-emission way of living. One of the key avenues to keep things in a manageable state is boosting utilisation of low-emission renewable energy resources – including solar, geothermal, wind and marine. From an Aotearoa New Zealand perspective, we are blessed with significant resources in all these flavours.

"This new article is a useful global survey of tidal energy hotspots – one of the leading varieties of marine energy. The hotspots are locations where the shape of the continents and islands interplays with the ocean tides to create regions with very strong ocean currents. These ocean currents are a form of energy just like wind – only with the greater density of seawater compared to air – much more energy. The last several decades has seen the development of technology to capture this energy. While there are many challenges, one of its major advantages is it is relatively predictable.

"The article makes the point that Aotearoa has a very substantial energy resource in the tides of Cook Strait | Te Moana o Raukawa and that singular installations can make a big impact nationally. This is true and well-established and a great reminder of the amazing environment on our doorstep. The nature of the twice-daily tide, the shape of Aotearoa’s main islands, and the contraction associated with the strait all mean there is a very large concentration of kinetic energy in the region.

"However, the reality of energy extraction is it is exactly that – a removal of energy from a system. Such extraction at the suggested scale would be excessively impactful from almost any perspective you care to choose. The way to view the opportunity is in terms of its contribution to an ecosystem of renewable energy resources along with more energy efficient ways of living and thriving. So modest scale tidal energy farms in constrained areas makes for a much more realistic future. While this may seem like a big challenge it is important to recognise that 'business as usual' is not an option in a shifting climate system."