Opposition to something is fine but coming up with a better alternative tends to give an argument more clout.
That's why the Green Party's proposal to turn the Whanganui and South Taranaki coast into New Zealand's largest marine mammal sanctuary will be a further boost to those who don't want a bar of seabed mining in the area.
The opposition to Trans-Tasman Resources' planned iron sand mining operation off the coast of Patea has been overwhelming and stands alone purely on environmental grounds.
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But the flipside has always been the economic benefits.
There's plenty of scepticism around how much money really would have come into the region and if it would be worth it.
But money could rightly remain a lure for some, especially in places that could do with it.
What the Greens have done with the marine mammal sanctuary idea is say 'you can have your cake and eat it too'.
In announcing the policy this week, Green Party leader James Shaw said it would be a chance to create an eco-tourism industry if the area became known for the sanctuary and its blue whales.
In other words making money while protecting the environment.
Granted, the local economic benefits from the proposed sanctuary are as unproven as the benefits of mining but there's no question which wins on the environmental front.
There are hurdles too.
TTR's clearance from the Environmental Protection Agency this month will need to be overturned (appeals are under way) and the Greens would need to win support from at least the Labour Party and for them to be in Government.
All far from guaranteed.
But the Greens have added another strand to the argument against seabed mining.
They're not just saying 'no thanks'. They're saying 'no thanks, but how about this'?