In regards to Olive based World Heritage Sites, I remember hearing an interview with Carol Drinkwater where she propossed the idea of an "
Olive Route" WHS, similar to the Silk Route. She wrote a book about it which
you can read the start of here.
Czechia (still not sure on that usage) has two agricultural sites on its t-list:
Žatec -the Hops town as the name suggests is about the most important Czech crop Hops! For those that know their brewing well Žatec hops (as well as many other Czech beer products) are known more widely by its German name
Saaz. It is also the primary flavouring in one of the world's greatest products
Pilsner Urquell.
Fishpond Network in the Třeboň Basin is actually an agricultural site, focused on the rearing of fish.
Neither are exceptional to my mind, but probably the match of any old wine region that is flinging itself at the list in order to up it's premium brand positioning.
I think the idea of Keralan sites associated with spice would certainly get my backing, I didn't realise that the Mattancherry Spice Market Colvin spoke of was the same one I knew as the
Cochin Spice Market, being British I can attest to the
influence of the Indian Spice trade.