I won't pretend like I'm an expert. My knowledge wasn't coming from Wiki though, but I wanted to both be sure and provide a source if possible before sharing my opinion. If you're saying that information on the link is all about the sea itself and not have any impact on the region, alright. I won't discuss it, you may be right.
However, you completely misunderstood me apparently. I wasn't trying to say the Mediterranean region is a whole desert. I'm saying not every region in the Mediterranean is fertile, in fact, lands that are fertile are in minority. Also the diversity of goods, in general, were not good too due to the climate. For these reasons people looked for trade more in the Mediterranean is what I'm trying to say. Mesopotamia is not in the Mediterranean region actually, but yes there are fertile regions too. Egypt was a bread basket by itself, for instance, I know that. If you are an expert, don't hesitate to enlighten me, my information is mostly from a historian I listened to a while ago.
In short, countries shouldn't be in a food abundance and should need to trade in general.
Yes, not all regions where that fertile, although it has to keep in mind that the climate in mediterranean region was also warmer from bronze age to late antiquity than nowadays and some regions like in North Africa, Carthage region were more fertile than they are today, how much more isn´t that clear and historians are argueing about that up to today, if it was just clearly more fertile land at those times or if they just had better irrigation technology and administration, compared to other regions and if that was, what made these regions so grain rich and exporting at those times.
From
Wiki: "Average wheat yields per year in the 3rd decade of the century, sowing 135 kg/ha of seed, were around 1,200 kg/ha in Italy and Sicily, 1,710 kg/ha in Egypt, 269 kg/ha in
Cyrenaica, Tunisia at 400 kg/ha, and Algeria at 540 kg/ha, Greece at 620 kg/ha.
[39] This makes the Mediterranean very difficult to average over all. "
Anyway, the huge grain producers were the ones which impacted and stimulated the whole economy in the mediterranean region the most. Those rich noble families and/or states got rich through grain and only this wealth made them capable to import luxory goods like wine, iron, gold, silver from other areas. If we take away the rich grain empires, the economy of not rich, but small states or tribe regions like Iberia f.e., their income should also decrease, maybe into poverty, as they have no one anymore to sell their goods too and those states definetly had no other great means of income like grain.
Grain was the engine of international trade at those times and grain was what made most people and states rich, all the other goods were only supplements to the economy, even if they had higher prices and better margins. Speaking from a states view (like we are in IR) or from a noble family owning lots of hectares. You would sell lets say 1000 Tonnes of grain per year and only maybe 80 Tonnes of Wine production. If you own a Mine, maybe 50 Tonnes of Iron per year. Small supplements to the big money maker "Grain".
Romes annual metal production at highest peak in late empire:
Compared to estimation of grain needed to feed only Rome the City, but not the whole empire and also without exports, but should give us a good estimation how many tonnes of grain where traded overall
Wiki:
"Rickman estimated that Rome needed 40 million
modii (200,000 tonnes) of grain per year to feed its population.
[45] Erdkamp estimated that the amount needed would be at least 150,000 tonnes, calculating that each resident of the city consumed 200 kilograms (440 lb) of grain per year.
[46] The total population of Rome assumed in calculating these estimates was between 750,000 and one million people. David Mattingly and Gregory Aldrete
[47] estimated the amount of imported grain at 237,000 tonnes for 1 million inhabitants;
[48] This amount of grain would provide 2,326 calories daily per person not including other foods such as meats, seafood, fruit, legumes, vegetable and dairy. In the Historia Augusta, it is stated Severus left 27 million modii in storage - considered to be a figure for the canon at the end of the 4th century and enough for 800,000 inhabitants at 500 lbs of bread per person per annum
[49]"