Grazing is often the main factor and wild rabbits have often been recognized as the main culprits.
Using historical evidence chiefly based on farming reports from the Coleraine Chronicle it is possible to show how variable and often dramatic the impact of rabbits has been since the early 19th century. As early as 1804 the rabbit's potential population growth and environmental impact were recorded. Numbers were kept under control until the early 20th century as many rabbits were killed for their meat or fur. By 1924 rabbits were considered a plague in many parts of the north of Ireland. Attempts to control them failed until the 1939-1945 war effort to increase food production nearly eliminated rabbit.