Dragonfly communities in tropical rainforest streams in Malaysian Borneo are heavily affected by selective logging and conversion of surrounding land to oil palm plantations.
A study led by researchers at the University of Cambridge, and carried out at the Stability of Altered Forest Ecosystems (SAFE) Project in Sabah, Malaysian Borneo, found that communities of both adult dragonflies and their larvae were substantially different in oil palm and logged forest streams compared to streams in old growth forests.
The team surveyed adult and larval dragonflies across 16 streams, including streams surrounded by old growth forest, selectively logged forest of different qualities, and oil palm plantations. Some of the oil palm plantation streams had narrow strips of forest left along their banks (riparian buffers), whilst others had oil palm growing right to the water’s edge.
Very different sets of species were found across the sites, with more widespread and common dragonflies, and fewer forest-dependent and range-restricted damselflies, found at sites surrounded by oil palm or heavily logged forest, compared to old growth forest streams. There were also fewer larvae in oil palm plantation streams, than in streams surrounded by higher quality forest, suggesting that dragonflies and damselflies are using these streams much less for breeding, or that larvae are surviving less well in oil palm streams.
Having riparian buffers around streams in oil palm seems to offer s¬ome protection for forest-associated dragonflies, but only if the buffers are wide, and mostly for adults rather than larvae. Efforts to protect forest dragonfly communities should therefore focus on conserving remaining forest areas, but good management and preservation of forested riparian buffers in oil palm plantations could also be highly valuable.
This work is published in the open access paper “The impacts of habitat disturbance on adult and larval dragonflies (Odonata) in rainforest streams in Sabah, Malaysian Borneo” in the journal Freshwater Biology (available at http://onlinelibrary.wiley.com/doi/10.1111/fwb.12880/abstract) by Sarah H Luke, Rory A Dow, Stephen Butler, Chey Vun Khen, David C Aldridge, William A Foster and Edgar C Turner.
1) Dragonfly assemblages (Odonata: comprising damselflies, Zygoptera; and dragonflies, Anisoptera) in Southeast Asian rainforests are extremely diverse but increasingly threatened by habitat disturbance, including logging and conversion of forest to oil palm plantations.
2) Land-use change can affect dragonfly larval stages by altering within-stream environmental conditions, and adults by loss of perches, shade and hunting habitat. However, the extent to which dragonflies are affected by land-use change is not well known, and strategies for conservation are poorly developed.
3) We surveyed dragonfly adults and larvae, forest quality and stream environmental conditions across 16 streams in Sabah, Malaysia. Habitat surrounding the streams included pristine forest, selectively logged forest, oil palm with forested riparian buffer strips and oil palm without buffers.
4)Overall abundance and species richness of adult dragonflies stayed constant with habitat disturbance, but larval abundance and richness decreased with higher habitat disturbance, and larvae were largely absent from oil palm streams. There was also a clear shift in community composition of both adult and larval dragonflies. Anisoptera adults were more species rich and abundant, but Zygoptera adults were less species rich in more disturbed sites.
5) The presence of riparian buffers in oil palm plantations offered some protection for forest-associated dragonfly species, and streams with wider riparian buffers supported adult assemblages more similar to those found in logged forest. However, oil palm streams with riparian buffers still contained a depauperate larval assemblage compared to logged forest areas, and dragonfly assemblages in narrow riparian buffer streams were similar to those found in streams surrounded by continuous oil palm.
6) Our results provide clear evidence of the effect of land-use change on dragonflies. Conservation efforts to conserve forest communities should target the preservation of existing forest areas, but management within oil palm plantation landscapes to preserve riparian buffers can still have a marked beneficial effect on dragonfly communities.