Amusingly enough, renewable power operators would be a good bet. If Global trade collapsed then they'll have an enormous advantage over fossil fuels because they don't have to import coal/oil/gas from across the globe.

> If I invest in agricultural companies in Greenland, what protects them from being pushed out by Spanish agricultural companies that buy up land in Greenland? That would especially suck if I shorted the Spanish companies.

If the world get's messed up enough that Greenland becomes an important source of agriculture then you'll want all your investments to be local.