 In the late Middle Ages , average temperatures began to reduce again , with cooler and wetter conditions limiting the extent of arable agriculture , particularly in the Highlands . The introduction of new monastic orders such as the Cistercians in this period also brought innovations in agriculture . Their monasteries became major landholders , particularly in the Borders . They were sheep farmers and producers of wool for the markets in Flanders . By the late Middle Ages , Melrose Abbey and the Earl of Douglas had about 15 @,@ 000 sheep apiece , making them among the largest sheep farmers in Europe . 
