Agriculture in Scotland in the Middle Ages includes all forms of farm production in the modern boundaries of Scotland, between the departure of the Romans from Britain in the fifth century and the establishment of the Renaissance in the early sixteenth century. Scotland has between a fifth and a sixth of the amount of the arable or good pastoral land of England and Wales, mostly located in the south and east. Heavy rainfall encouraged the spread of acidic blanket peat bog, which with wind and salt spray, made most of the western islands treeless. The existence of hills, mountains, quicksands and marshes made internal communication and agriculture difficult. Most farms had to produce a self-sufficient diet of meat, dairy products and cereals, supplemented by hunter-gathering. The early Middle Ages were a period of climate deterioration resulting in more land becoming unproductive. Farming was based around a single homestead or a small cluster of three or four homes, each probably containing a nuclear family and cattle were the most important domesticated animal.