Answer: 2. It emphasizes the author's reverence for the seeds.
Step-by-step explanation:
Buried pirate gold or any gold for that matter, is very valuable and the author acknowledges this fact. The author however goes on to say that the value of seed banks cannot be measured unlike gold which can.
This shows that to the author, seed banks are much more valuable than pirate gold which means that the author attaches great reverence to seed banks and by comparing them to seed banks, this reverence is made more apparent.