Decrease is a synonym of Contract. Contract is a synonym of Agree. Agree is related to Consent. 
Supply is related to Crop. Crop is related to Short. Short is the opposite of Broad. 
Decrease <--Synonym--> Contract <--Synonym--> Agree <--RelatedTo--> Consent 
Supply <--RelatedTo--> Crop <--RelatedTo--> Short <--Antonym--> Broad 