re: Many food and agricultural varieties going "extinct"?

Biodiversity is a good thing, IMHO. There's a line--eat it to save it--that applies to less widely grown varieties of fruits/veg. Check out the Seed Savers Exchange, a nonprofit seed bank that tries to preserve and encourage planting diversity. LINK / You can shop for seeds on the website.

Smaller scale agriculture is better for the planet. But we would need to wean ourselves from the cereal crops that underpin the US diet: the corn & soy & wheat in processed foods and in animal feeds. Our cheap meats are made possible through those giant cereal monocultural fields across the Plains & Midwest.

In short, if you abhor Big Ag & monoculture farming, don't just buy local produce: quit eating factory meat.