Sirtsi Nature Conservation Area (NCA) consists of a range of mires in the north-west – south-east direction with a bog, rich in hollows and pools in the middle and quagmires on the edges. The mire with total area of 5644 ha lays in a basin formed by glacial lake as a result of paludification of the area.
Following classification of the Estonian vegetation site types (extract from Paal, 1997) most of the area is covered by hummock bog site type, hollow-ridge bog site type, and pool-ridge bog site type. In addition, mixotrophic (transitional) grass mire type, treed hummock bog site type and treed mixotrophic (transitional) grass mire type were determined.
In 2009 an inventory of drainage systems was initiated by Environmental Board and implemented by Estonian Fund for Nature. This provided information regarding the situation of drainage, also the activities of beavers and provides a basis for restoration activities. Additional survey was carried out by Tallinn University, Institute of Ecology in 2010. This revealed that approximately 60% of the Sirtsi mire complex covering 3713.1 ha (with minimum peat depth of 30 cm) is under natural or close to natural conditions. Drainage zone covers 1077 ha of mire area and additional impacted area is estimated to be 300 to 400 ha. The impact zone, caused by drainage, covers mainly margin areas, and drained peatland forests have been formed.
Sirtsi project area includes also former peat mining area with very deep and dense drainage network and totally destroyed vegetation. Those deep ditches influence wider area compared to ordinary ditches and therefore their closure is of higher priority. Restoration of vegetation cover in former mining area is planned via Sphagnum planting.