The publication of the book "The Locavore's Dilemma", which argues, sometimes rather bluntly, against basing your diet purely on local produce, has instigated an interesting, widespread discussion on the arguments for locavorism versus globavorism (see some links below).
The arguments presented on both sides make it increasingly clear that, as is the issue with similar debates on for instance meat vs. vegetables or organic vs. conventional, there is no obvious winner if all aspects are taken into account.
A wide-ranging, evidence-based review on the impact of the geography of individual diets is needed but it seems that the solution eventually will turn out to be a geographically balanced diet, which could be called Geovorism. This would mean eating local produce where it makes most sense from an environmental, social and health point of view, and supplementing this (to achieve a healthy, balanced diet) with produce from further away, but choosing again in a knowledgeable manner based on the information available.
The Locavore's Dilemma
Economics and the Locavore's Dilemma
Is local food bad for the economy?