Reducing food imports?

I'm playing RTR platinum 1.8, and cities often have ridiculous levels of food imports, such as 8.5%, on top of whatever other growth bonuses they have, resulting in enormous cities. Does anyone know what governs the level of food imports, and thus how one can reduce this?

I'm afraid I don't know, normally imports is to do with resources, but I don't think it's the same for food...

It will be effected if the import resource is grain - grain has a (hard coded ?) effect on growth so that's likely to be the cause.

Grain is a visible resource - locate it's position on the campaign map, find its co-ordinates (use show_cursorstat in rome shell) and then comment out the appropriate line in descr_strat.txt. Think you'll need to delete map.rwm and re-start the campaign for that change to take effect and it will probably have an effect on the economy as well so you might actually prefer to put another resource in its place.

You could alternatively lower the base growth rate for that region in descr_regions.txt.