The largest deserts on Earth are not on land. They are the oceans. They are vast empty spaces, devoid of macrobiota. Most people think the oceans are full of fish, and that is due to the fact that very few people have really been away from the continental shelves, and out into the deeps.
I am always amazed at how truly empty the oceans are, both on the surface, and below. It is so empty that your nose forgets the smells of land. When I crossed from Papeete to the Marquesas, we could smell Fatu Hiva long before we ever saw its ragged skyline. It is so empty that a swim becomes a fright when you look down, and realize that the bottom is three miles away.
Far from land, the only things that survive are the bigger ones -fish like tuna & mackerel, turtles and whales, etc.- the things that can survive a crossing from island chain to island chain, hopping from guyot to guyot. Away from the shallows, there just isn't enough of an ecosystem to support many fish. That's why we have always fished in places like George's Bank, and not far out over the benthic deeps. That's why people marooned on the high seas are at risk of starvation.
And that's why fisheries management is such a big deal. We can't just fish elsewhere - we're already fishing eyerywhere. And we also barely know what we are managing: for most species, we don't really understand the population dynamics, and what sparse data we have is often outdated. Imagine an agricultural system where we went out with large earthmoving equipment like graders and caterpillars, clearcutting a forest, and then sorting out the resulting heap to find if we got any corn. In a January 17 post, I touched on the issue of having the sea supplement the land for feeding - building on Antony Trewavas' phrasing, I would call the fishing industry today "fully mechanized hunter-gathering."
So don't look to the sea for mankind's salvation: it is mostly a barren place, good for contemplation and introspection, but not for feeding many more desperate millions. We are already probably pushing its feeding capacity limits, and are possibly near a bifurcation point of a complex, non-linear, dynamic system that could suddenly shift into a completely different regime -- one where we have no knowledge of its behaviour, and worse, one where we have no place.
Hand written on a Newton, and submitted wirelessly from bed.