Habitat specialist dragonfly

They are at home near lakes and rivers - the 70 or so dragonfly species in Lower Saxony. However, one in three of their species is endangered, including the green mosaic dragonfly. The Vegetation Science and Nature Conservation working group is now working to preserve them.

The aim of the working group, which is headed by biologist Prof Dr Rainer Buchwald, is to plan and implement conservation measures for the green mosaic dragonfly. He is cooperating with the Wüsting and Stedingen water maintenance associations, the districts of Oldenburg and Wesermarsch and the city of Oldenburg. The German Federal Environmental Foundation (DBU) is funding the co-operation project until 2014.

The focus of the scientific investigations is on dispersal behaviour and population dynamics. Based on this data, Buchwald's working group intends to design species protection measures in cooperation with the respective environmental agencies and maintenance associations and test them on site.

The green mosaic damselfly is bound to water bodies in which the crayfish claw (Stratiotes aloides), an aquatic plant species from the frog-bit family, occurs. If dense crayfish claw populations are present, the dragonfly species colonises ditches, flowing waters with low currents and still waters. In the project area, it can be found in crayfish claw ditches in the Bornhorster Huntewiesen nature reserve, in Oberhausen/Hude and near Berne.

"The green mosaic dragonfly lays its eggs exclusively in this rare aquatic plant," explains Buchwald. This is why the dragonfly is considered an extreme habitat specialist and can be described as a character species of crayfish claw waters. The vegetation expert therefore believes that an important measure to protect the green mosaic dragonfly is to safeguard dense populations of crayfish claw: "We need water protection that takes into account the life cycles and ecological requirements of both the dragonfly and the aquatic plant species," emphasises Buchwald.

"In addition, crayfish claw populations should be re-established in suitable bodies of water." This would create new habitats for the endangered dragonfly species and improve the connectivity of widely separated habitats. A start has been made: In recent weeks, initial measures have taken place in the Wesermarsch and the district of Oldenburg.