As you might expect, it’s complicated. The World Banana Forum of the Food and Agriculture Organization of the United Nations has prepared an analysis of the carbon footprint of the banana supply chain.
To give you a Readers’ Digest version the WBF states that the primary production stage (preparation of the fields, transport on the farm itself, application of fertilizers and pesticides, harvesting, and packaging) have the lowest impact, contributing 16-20 percent of greenhouse gas emissions. It should be no surprise that transportation accounts for the most GHG emissions, between an estimated 62 to 67 percent. Here is a link to that article: