I guess what strikes me the most about this map is the huge blank spaces among the world’s global shipping routes: the Bay of Bengal, southern Australia, the west coast of South America, and pretty much all of sub-Saharan Africa that isn’t connected to either South Africa or the Gulf of Guinea. Of these, Australia at least has a viable road network. Relative to the entirety of the world, these don’t look like large spaces, but the increased costs for closing these gaps via land are not insignificant.
Another thing that comes to mind here is imagining how the shifts in shipping patterns may have happened over the centuries. Never mind the obvious growth in gross number of journeys; what I’m thinking of here is the opening up of new routes.
I’m not a shipping person, but I try to be as much of a history person as I can. Off the top of my head, I would venture that China’s periodic bouts with isolationism over the centuries have had material effects on the Asia routes, the most recent probably being a massive dropoff during the 1950s through sometime in the 1970s as China re-opened and Japan started coming online. And transatlantic development from the Industrial Revolution forward has kind of been done to death.
There’s also this book, which I’ve yet to read but has been on my to-do list since it came out. I suppose where this all leads is, what’s the future of this map? More specifically, how much of south-south trade development will any of us live to see?