Threats

The biggest threat to dragonflies and damselflies probably comes from loss of habitat, changes in land management and urban/industrial development.

Pollution is a major cause of concern, especially sewerage, industrial effluents, diesel, excess sediments, run-off from fertilisers used in agriculture, wind drift from insecticides, and the consequences of using herbicides on marginal vegetation. Pollution may be particularly devastating in streams, rivers and pools or lochs with inflows.

Aquatic habitats used by odonates (damselflies and dragonflies) may be lost through drainage or over-abstraction of a watercourse. Serious impacts on flowing water species can also occur following the canalisation of rivers or as a consequence of certain flood prevention schemes.

Species with a northerly distribution, such as the Azure hawker, the Northern emerald and the White-faced darter mentioned earlier, may be severely affected if temperatures rise as a result of climate change. The drying out of small bog pools, as a result of either drainage or climate change, or a combination of both, could be particularly disastrous for the Azure hawker with a larval life that can extend for up to four years

Male Northern Damselfly Coenagrion hastulatum

Male Northern damselfly Coenagrion hastulatum
© D.Goddard

Changes in land management may take several forms, and one of the most harmful to Odonata habitat in Scotland, side by side with destructive peat cuttings on an industrial scale, may well be afforestation. The Northern damselfly, for instance, has been lost from one of its long-established site due to the combined effects of afforestation and drainage. Conservation work in Speyside, blocking drains to improve the habitat for birds has, unintentionally, created suitable temporary habitats for this damselfly species, but these provisional havens may become unsuitable if the water levels cannot be maintained.

Inappropriate habitat management can have catastrophic impacts. Drastic modifications to water bodies or their surrounding vegetation can eradicate populations. At the other end of the scale, a complete lack of management can result in the water being shaded out by surrounding trees and shrubs or choked with silt and plants accumulated over the years.

Overstocking ponds with fish has immediate negative impacts as they are natural predators of dragonfly larvae. In addition, bottom-feeders such as carp disturb sediments, which can muddy waters to such an extent that submerged plants cannot grow any longer and in turn make the site unsuitable for dragonflies.

Widlfowl can cause physical damage to the banks through much trampling and grazing of the marginal vegetation and are a source of chemical pollution due to nutrient enrichment from their droppings. Disproportionate nutrient input can, for instance, cause algal blooms and excessive growth of duckweed, which in turn prevent any light getting into the water, any plant growth and any aquatic insect life.

Excessive wave action from boat drift and other unnatural fluctuations in water levels can have severe impacts on odonate populations as well, either through direct impact at the peak of dragonfly emergence, or indirectly through damage to marginal vegetation and erosion.