I’m not the one who posted the initial response, I’m just explaining what they meant.

Also, this isn’t intended to be dismissive or insulting because I recognize that everyone comes from different backgrounds and experiences, but it’s pretty widely known that different crops have different labor costs. Everyday is a chance to learn something new though. Here’s a quick overview from UC Davis on the subject.

I’d also recommend the book Fresh Fruit, Broken Bodies if you want a more personal, on-the-ground understanding of (some of) the human costs of agriculture. Understand that no book can cover everything though and there’s much worse costs than anything it covers.

None of this human cost is inherently related to concepts like monocropping either. Rather, they’re related to the economic and political context agriculture exists in, especially how those impact current mechanisation capabilities. Harvesting things like cereals is so efficient in large part because of the huge demand from livestock agriculture for cheap feedstock to justify the development/purchase of things like combine harvesters.

Some crops aren’t heavily mechanized though, and modern agriculture hires cheap laborers instead. These tend to be the expensive things at the grocery store for fairly obvious reasons, but not always. If you’re buying Spanish produce in Europe (e.g. bell peppers), there’s a reasonable chance it was harvested by migrant workers working under inhumane conditions in a greenhouse. Things like coconuts tend to have slavery and animal cruelty in their supply chains and that’s the basis for a good chunk of cuisine in South Asia.

Another way to directly tie specific crops to their human costs is to look at the daily dead body reports by US border patrol. They tend to spike a couple weeks before/after certain crop harvests. Strawberries and tomatoes show up particularly strongly in this kind of analysis, which is why I mentioned them. You can also see the spikes from things like grapes, lettuce and beans.

It’s true that plant based diets use fewer resources (inherently true because of net productivity works), but it’s not what the parent comment is talking about. Fodder crops are not hand harvested. They’re harvested with big machines as cheaply as possible. If you add another acre or 20 of barley to the world, there may not be a single additional person helping to harvest it.

The parent comment is drawing a contrast with human crops like tomatoes and strawberries that are typically harvested by backbreaking manual labor.