Marine scientist ANDREW WRIGHT looks at seismic surveys and marine mammals, the bias, the myth and what we really know.

OPINION: On 15 November, Amanda Larsson from Greenpeace told us that "blasts" from seismic surveys using "air cannons" are "likely to be torturous" to blue whales in the newly discovered habitat off the Taranaki Coast.

On 16 November, Cameron Madgwick from Petroleum Exploration and Production Association of New Zealand (PEPANZ) proclaimed that there is "no clear international evidence to suggest marine life are impacted by these surveys" and that its regulation means there is no danger.

DOC A blue whale near a drilling rig off the Taranaki coastline.

Greenpeace have an agenda to stop seismic surveys and fossil fuel production. PEPANZ represent an industry that makes huge amounts of money from fossil fuel production. Both have conflicts of interest. But who is telling the truth?

Well, both and neither, depending on your perspective and how you define words. So let's take a look at what we actually know.

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ILLYA MCLELLAN/STUFF A blue whale carcass washed ashore at Glenburn Station in Wairarapa.

Firstly, seismic surveys currently use a piece of equipment called "air gun," not an "air cannon". These are towed in large numbers to create sounds that are very loud.

Cameron notes that nature can produce similarly loud sounds. This is true, however seismic surveys add sound to the environment on top of these, meaning that the comparison is not helpful. Consider that an avalanche is as loud as a firework and louder that a pistol shot. But that would not mean you want to be right next to a firework or a gun as it goes off. Especially once every 8-12 seconds for three months.

Next, let's consider Cameron's claim that animals are smart enough to move away, along with the claim on a new pro-industry website set up by PEPANZ that claims that seismic surveys do not "harm" marine life (seismicsurvey.co.nz).

DEBRA GLASGOW A blue whales spotted by NIWA scientists on a research expedition in the South Taranaki Bight.

Yes, dolphins are smart. However, if they do leave, that means that part of their habitat is unavailable to them. This loss of habitat doesn't necessarily "harm" them in the same way that cutting down a rainforest doesn't "harm" an orangutan, but ultimately it puts the species at risk.

Of course, Cameron will assert that seismic surveys are temporary, and the habitat is returned. However, if oil is discovered, such surveys will be needed throughout the life of the oil field.

Furthermore, some animals may be unable to simply move away. The Maui dolphin, for example, lives along a very fine strip of water along the coastline of the West Coast of the North Island. If a seismic survey is offshore, it simply has nowhere to go.

Enough debunking – here's what we actually know.

We know that loud sounds can damage the ears of marine mammals. If they get close enough to a seismic survey they undoubtedly will have some level of hearing loss. This is clearly important for animals that rely on sound for breeding, hunting, and communicating.

We have no evidence that seismic surveys do, or do not, directly cause populations of marine mammals to decline. However, we do know that noise exposure induces a stress response in whales, in much the same way as living near a noisy street will lead to a stress response in humans.

Through extensive, multi-year studies we know that such stress responses, when maintained over the long-term, can lead to increased risk of heart disease, lower fertility, and cognitive disorders in humans. Although we are unable to replicate such studies in whales, there is no reason to assume that they do not suffer in similar ways. And increased mortality coupled with decreased reproduction is never going to be good for an already endangered species. Cognitive disorders are also troubling for intelligent species.

In short, we know that seismic surveys can cause hearing damage, are likely to cause stress and, by implication thereof, are likely to be having an impact on the population level. We may not have evidence that this last piece is actually occurring, but we don't actually need to know it is occurring.

If you leave an open yoghurt at the back of your fridge for a month, you don't need to look at it to know it is no longer fit for consumption. You have enough information about how the world works to know it is becoming a small experiment in microbiology back there. As a result, if you did look at it and find it was still good to eat, you would be extremely surprised.

This is what we know about seismic surveys. We also know that the climate is changing and that we have a responsibility to do our bit to reduce carbon production. Any suggestion that New Zealand's decisions on fossil fuels and climate action can have little or no influence on the world is somewhat insulting. Developing new technologies here that could be exported to the world as others take up more responsible climate policies could place New Zealand at the forefront of the renewable revolution, instead of at the back of the fossil fuel pack.

Finally, some seismic surveys may be regulated in New Zealand, but foreign research surveys are not, despite the existence of the Marine Mammals Protection Act. In any case, guns are regulated around the world, and people still get shot. Vehicle safety is highly regulated, and people still die in car crashes.

Regulation does not prevent damage for us, why should we expect that it can prevent damage to the whales?

Dr Andrew Wright is a marine mammal expert at the University of Canterbury.