Complex sentence: Formerly most of the land was in agriculture, chiefly dairy but since the end of the nineteenth century, farm abandonment has increased and, today, forest cover and early succession forest regrowth dominate the landscape mixed with remaining dairy farms.
Split into simpler sentences: Formerly most of the land was in agriculture, chiefly dairy. Since the end of the nineteenth century, farm abandonment has increased, and today forest cover and early succession forest regrowth dominate the landscape mixed with remaining dairy farms.