What caused seed abundance to decrease from 1975 to 1978

The finch population decreased.

Explanation:

When finches eat seeds, some pieces fall onto the ground which grow up to have more seeds. The seeds that survived were too big for a finches tiny beak. Without this cycle in place, seeds had no way to reproduce.

answer: i don't know

explanation:

you need to provide a picture, otherwise i can't tell you.

if you can provide one, i'd be more than happy to you with this!