Loss of organic matter occurs both in peat and mineral soils. Decomposition of drained agricultural peat soils is an underestimated source of loss of organic matter and causes water pollution and CO2 emissions. Subsidence rates of 1 – 2 cm per year are not uncommon and make peat soils below sea or inland water levels prone to flooding. Loss of organic matter in mineral soils is due to long-term agriculture, and is recognised as a problem in large parts of Europe. Monocultures, reduced use of organic amendments (particularly farmyard manure) and intensive tillage, are recognized as major factors affecting SOM (soil organic matter) turnover.