How much better is local food for the environment?

Local food can consume more energy, especially when it is shipped — even short distances — by truck.  Here is from The Boston Globe:

…a gathering body of evidence suggests that local food can sometimes
consume more energy — and produce more greenhouse gases — than food
imported from great distances. Moving food by train or ship is quite
efficient, pound for pound, and transportation can often be a
relatively small part of the total energy "footprint" of food compared
with growing, packaging, or, for that matter, cooking it. A head of
lettuce grown in Vermont may have less of an energy impact than one
shipped up from Chile. But grow that Vermont lettuce late in the season
in a heated greenhouse and its energy impact leapfrogs the imported
option. So while local food may have its benefits, helping with climate
change is not always one of them.

And more:

Judged by unit of weight, ship and rail transport in particular are
highly energy efficient. Financial considerations force shippers to
pack as much as they can into their cargo containers, whether they’re
being carried by ship, rail, or truck, and to ensure that they rarely
make a return trip empty. And because of their size, container ships
and trains enjoy impressive economies of scale. The marginal extra
energy it takes to transport a single bunch of bananas packed in with
60,000 tons of other cargo on a container ship is more than an order of
magnitude less than that required to move them with a couple hundred
pounds of cargo in a car or small truck.

Yes even grapes from Chile end up on a truck but perhaps on a more efficient truck.  Why is there no talk of how they are transported from the Chilean vine to the Chilean port?  Here is a previous post on this topic.