Our World in Data has an article with a series of very interesting graphics about the environmental impact of food, such as this one:
The most important insight: It hardly matters where your food comes from. What matters is what you eat.
Transport is a small contributor to emissions. For most food products, it accounts for less than 10%, and it’s much smaller for the largest GHG emitters. In beef from beef herds, it’s 0.5%. […]
There are also a number of cases where eating locally might in fact increase emissions. In most countries, many foods can only be grown and harvested at certain times of the year. But consumers want them year-round. This gives us three options: import goods from countries where they are in-season; use energy-intensive production methods (such as greenhouses) to produce them year-round; or use refrigeration and other preservation methods to store them for several months. There are many examples of studies which show that importing often has a lower footprint.
The second one: not surprisingly, plant based products have a far smaller carbon footprint: