The Single Farm Payment
The subsidy for farmers comes in the form of the Single Farm Payment - an amount received per hectare - provided that they keep the land in a government-approved state. Specifically, they must avoid the "encroachment of unwanted vegetation on agricultural land". In other words, they have to keep the land clear of wildflowers, trees and shrubs: all those things which provide a habitat for wildlife.
5.6 million hectares - some 71% - of Scotland's land is in agricultural holdings.
Without public subsidy, the majority of hill farming would be unsustainable. Few would challenge that assertion. If farmers want to increase the amount of money they receive, they simply have to clear more land.
It is possible that the Single Farm Payment is the biggest barrier to rewilding in Scotland.