The Peregrine."...the Solarian's own needs were adequately provided for at home; he had no particular reason to haul goods out to the stars. The interstellar colonists had to provide for themselves." (CHAPTER VI, p. 38)
So Earth would not be plunged into derivation and want if interstellar contacts were to be interrupted. And the same would apply to colonies like Nerthus, capable of growing their own food as well as any crops for export.
"A small but brisk trade went on between the stars of any given sector, carried by merchant ships or by such Nomads as weren't heading out into the depthless yonder. A few goods from Sol itself, or other highly civilized systems, found their way out to the frontier, too." (pp. 38-39)
A small trade within each sector, some of it dependent on the wandering Nomads; a few goods from Sol etc. Again, it sounds as if the colonies would be able to survive any disruption to trade, unlike Isaac Asimov's entirely urbanized planet, Trantor, which consumes the produce of twenty agricultural planets per day.
Trevelyan Michah expounds further:
"'Well, what have we today? A dozen or more highly civilized races, scattering themselves over this part of the Galaxy, intercourse limited to spaceships that may need weeks to get from one sun to the next - and nothing else. Not even the strong economic ties which did, after all, bind Europe to its colonies.'" (CHAPTER XII, p. 105)
It is a pity that we see so little of those other races. We see one Reardonite. The Tiunran are mentioned. We see four planet-bound species affected by space travellers. That is all. What a contrast to the Technic History where some of the narratives are histories not of human beings but of Ythrians or Merseians. But, in any case, CHAPTER XII confirms that there are no strong economic ties between Earth and its colonies. Planets can exist for weeks without any extra-systemic contact and presumably would continue to cope self-sufficiently if the intervals between contacts were to be extended.
Why then does Trevelyan go on to say:
"'Cross-purposes are breeding which are someday going to clash - they've already done so in several cases, and it's meant annihilation.'" (ibid.)?
What cross-purposes? Why should the clashes be serious enough to mean annihilation? We need to be shown some examples. Economic competition, imperialism, exploitation etc can certainly cause destructive conflicts but we are specifically told that economics is not a major interstellar factor. Planetary populations with mutually incompatible or incomprehensible psychologies, ideologies etc can each go their own way. There is no reason for them to go to all the trouble of crossing an interstellar distance just to pick a fight with someone else.
Regular blog readers will know that a day, like today, when I have visited Andrea above the Old Pier Bookshop is a day when there has been less time for blogging but that has been good for my soul.