MI10 Threatened mire species

>> Background information

Status

According to the latest species' red list assessment published in 2010 the share of mire species of all threatened species is 4.6%. This reflects the share mire species of all well-known species of Finland (4%) quite closely.

The total number of threatened mire species is 104. No less than half (53) of these live primarily on rich fens. Nearly all species groups include threatened rich fen species yet the greatest number of them can be found among vascular plants and mosses. The other half of threatened mire species is divided in nearly equal shares between species of fens (16%), pine mires (14%) and spruce mires (11%).

Vascular plants take up the largest share of all threatened mire species, 21%. The two other large species groups are butterflies 18% and mosses 17%. Besides being the primary habitat type of many species mires are also an important secondary habitat for a considerable number threatened species. Altogether there are 86 such species.

A regional study made on vascular plants and butterflies highlights the poor state of the mires and mire species' populations in southern Finland. Many of these species continue to have a viable populations in the northern half of the country, but in the south the populations are declining steeply due to habitat loss. Many of these species may also have a considerable excintion debt due to long generation span and rather poor ability to move between suitable habitat patches.

Development

By looking at species' verified class changes between the red list assessments of 2000 and 2010 the trend of threatened mire species seem quite clear. The red list classication of only four species has been lowered since 2000. Two of these species are birds: the populations of Great Grey Shrike and Pregrine Falcon have increased. The development of the latter is discussed in more detail below. The classification of Oak Spider and Grass Wave (a geometer moth) have also been changed in the positive direction.

The status of altogether 30 mire species has worsened. One thrid of the species are vascular plants. Several species with a negative class change also be found among birds, mosses and butterflies.

Detailled population monitoring data are available for the Peregrine Falcon since the 1970s. In the beginning of the monitoring period there were less than ten known Peregrine territories of the whole country and the species was nearing extiction. The species suffered heavily from persistent organic pollutants and persecution.

The number of territories has thereafter increased throughout the past four decades and the breeding population now totals some 300 pairs. Population increase has been especially steep during the first decade of the 21st century. However, the numbers of Peregrines are still far from the level of the early 20th century when 700?1000 pairs were estimated to breed in Finland. In the 2010 red list the Peregrine was classified as a vulnerable species.

Threats

The most important cause of threat to mire species is the draining peatlands for forestry and peat harvesting. It is the primary cause of threat to to more than half of all threatened mire species (59) and one cause among others to 80%.

Along with drainage for forestry mires have also been drained for agriculture. While the former, which has been done in order to increase tree growth, has been very widespread the latter has focused on more carefully selected types of peatland. The most nutrient and species rich fens were traditionally the most sought after sites for transition into fields. Therefore, despite affecting a restricted area, drainage for agriculture has had great impact on mire biodiversity. Most of the rich fens of southern Finland were converted into fields already before the 1950s. Today, only less than one percent of their original extent remains.

Other causes of threat to mire species include the building of infrastructure and waterways, overgrowth of open habitats as well as forest management measures. Of these, especially the first two building activities are often mentioned as a secondary cause of threat.