Nah, it's just that noone is making any kids and tons of young people have migrated elsewhere. The average lifespan of italians/greeks is pretty high, thanks to climate and diet. Italy/Greece have one of the lowest birth rates in the world. Italy is #190 and Greece is #181 in the world in fertility rates, with 1.3 and 1.4 births per woman.
For comparison, the US has 1.7 and Germany has 1.6. Spain and Portugal have 1.3. Japan has 1.3, China has 1.2 and Korea 0.9.
Looks like the author has just be ultra-strict about only showing countries with a Mediterranean coastline. Bosnia-Herzegovina does have a very small one, but Portugal doesn't
Although it would be quite funny to then include the UK on the basis of Gibraltar