According to Mike Berners-Lee’s book
How Bad Are Bananas, the carbon footprint of a banana is not particularly high for the average consumer; because bananas don’t necessarily require heavy packaging, and they are also filling and nutrient-rich foods. However, this may not be true for the concerned consumer, who would do a lot better for the environment by buying oranges grown in the state next door instead. Bananas have to be flown into western countries, which releases masses of CO2, and therefore significantly contributes to individual climate footprints.
In addition to this, bananas
are often packaged in plastic packaging, which is not only terrible for the environment, but is currently the only way most grocery stores choose to distinguish between fair trade bananas, organic ones, and cheap unethical ones.