Answer:
cyclical
Step-by-step explanation:
The keywords here are "during an economic downturn".
If the worker leaves the rural job temporarily (for one season/year for example), it's a cyclical change because he will return to his original occupation later when favorable conditions have returned
However, if that situation persists over a longer period of time, it will become a structural change and will cause a change of the structure of the work force, and a decline of the agricultural sector.
Without any further indication, I would go with cyclical.
A seasonal unemployment is for example an agricultural worker who doesn't have anything to do because of Winter. But he'll have work again once Winter has passed. Same concept for fishermen and tourism workers.