Are fish more important than jobs?

This evening I went to an excellent talk on the science of climate change by Prof Joanna Haigh. It was only slightly spoiled by four economics students sitting in front of me, who whispered and sniggered to each other throughout the whole thing. I tried passive-aggressive sighing but that didn't work – it was an hour before my frustration reached the point where I whispered "can you please stop talking" (they didn't). I spoke to one of them afterwards. He tried to make a point in relation to geo-engineering, which is the idea of using technology to artificially cool the planet. Prof Haigh had alluded to this at one point, talking about the idea of launching millions of tiny mirrors into space to reflect the sun's rays – something that would be incredibly expensive. The economics student wanted to know how cheap these mirrors would have to be before we would consider them a better solution than reducing emissions. I pointed out that the mirrors would be a very poor solution given that it would have to be maintained in perpetuity (any lapse would cause a sudden huge leap in global temperature) and would not solve ocean acidification – the absorption of carbon dioxide into the ocean which increases its acidity. His response to this was "so what?". I explained how ocean acidification is already reducing the ability of marine organisms to form shells, threatening the ocean food chain. He replied "so you think fish are more important than jobs?". He made the same point regarding the "environment" as a whole. My response was that we do not live in a bubble – we live in the environment, even if the modern world disguises this fact. To be fair, before about 10 years ago I was like most people – I mostly thought of being interested in the protection of "the environment" as a hobby that some people had, not all that different from enjoying dancing or making cakes. We necessarily form our views of the world from our personal experiences, and my personal experience of growing up was that of living in a house and getting food from a supermarket. It wasn't until I read Carl Sagan's "Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium" that I properly understood what a precarious situation we're in.