Conserving dragonflies (Odonata) along streams running through commercial forestry

Commercial afforestation of natural ecosystems is increasing worldwide. The re is little information however, on the extent to which biodiversity is be ing affected by this practice. This is especially so for stream fauna, incl uding the conspicuous Odon. Some dragonflies and damselflies may decline wh en their natural environment is anthropogenically changed and, as a group, they are sensitive to the impact of afforestation. The sires were four pine plantations in KwaZulu-Natal, South Africa. 14 environmental factors were recorded along stretches of streams running through each of the four sites. The diversity of Odon. spp. and their abundances along these streams were measured. There was a strong positive correlation between certain abiotic f actors, for example, boulder cover and shade, with the local distributions of these insects. Water pH was also a strong correlate. Most spp, required both unpolluted water and a sunlit stream. Particular vegetation type and e xact distance of pine trees from the water's edge (so long as they did not shade the stream) were not strong correlates. This meant that species diver sity dropped dramatically where the water was completely shaded by a closed canopy, whether it was from natural forest or from exotic trees. It is rec ommended that no plantation trees should shade a stream edge, and should be planted at least 30m from the water. All highly invasive, dense-canopy wee ds, especially Acacia mearnsii, should be removed, and extensive and intens ive cattle trampling of the banks avoided.