A recent report published in Science warns that within 50 years we won't have commercial fish.

If current trends of overfishing and pollution continue, the populations of just about all seafood face collapse by 2048, a team of ecologists and economists warns in a report in Friday's issue of the journal Science.

"Whether we looked at tide pools or studies over the entire world's ocean, we saw the same picture emerging. In losing species we lose the productivity and stability of entire ecosystems," said the lead author Boris Worm of Dalhousie University in Halifax, Nova Scotia.

Hmmm...okay. Just so happens I'm taking a course in macroevolution this semester, and it's taught by an ichthyologist. Now, he hasn't commented directly on this article, but in an interesting coincidence we were talking about mass extinctions last lecture.

There have been 5 mass extinctions in the history of multicellular life. In some cases, 99% of existing species were wiped off the planet. And life rebounded.

We're currently in a mass extinction, caused primarily by human expansion across the globe. But there are a couple of points.

Biodiversity is higher than it's ever been in the history of life. And what does it mean for an ecosystem to collapse? There are rare places on earth where no organisms live. There is usually turnover, and as a result the diversity often decreases, but it doesn't result in a barren landscape.

My professor made the point that human expansion and settlement is generally bad for specialized, narrowly adapted species that don't like much change (e.g. large animals with a limited range like gorillas, panthers, elephants, etc.), but is great for species that like a high trophic turnover and thrive on instability in the environment (this are "weed" species, like dandelions, cockroaches, and rats).

Another point he made specifically about marine fauna is that the trend of agriculture on land is now full force in the oceans. We've converted a ton of land to agriculture, and we're in the process of doing the same with lakes, rivers, and oceans. He pointed out that the Sea of Japan is basically one giant fishery now. The population of food fish there is tightly controlled and engineered.

Think of it this way, corn is not going extinct. We've probably driven a number of small, localized species to extinction by cultivating corn and taking over huge geographic areas to do it. So in those areas, species diversity is extremely low.

Is this a bad thing? Personally I don't think so. And I definitely don't believe that we're going to run out of fish within 50 years. And it won't be due to a loss of species diversity in the oceans, lakes, and rivers. I believe there will be a loss of species diversity, but I don't think it will result in a collapse of the ecosystem and the end of fish eating. If anything, we'll probably see the supply of commercial fish increase in the next 50 years, though it will probably be at the expense of many local aquatic species.