Tag Archives: invasive species

Can green roofs enhance conservation of biodiversity in cities?


Important pollinator populations grow more quickly in areas with urban and sub-urban gardens than flower-rich farmland. Allotment gardens have a greater diversity of nectar flowers compared with monocultures of crops in farmland, therefore support more populations of (for example) the buff-tailed bumblebee, Bombus terrestris terrestris. The close proximities of gardens in these urban parks allow pollinators to forage in a ‘matrix’ of gardens, each with a different floral make-up. But can roofs with built-in wild vegetation (green roofs) enhance biodiversity?

Green roofs are becoming increasingly common in cities as they absorb rainwater, regulate building temperatures (insulation), lower urban air temperatures and reduce the heat-island effect. These novel ecosystems also support generalist insect species, and scientists propose that they may also help conserve rare taxa, even vertebrates if connected to ground level habitats.

Williams and colleagues evaluated 6 hypotheses to test their effectiveness. They found that green roofs could aid rare species conservation if specific populations of species are targeted. For example, the Bay Checkerspot is an endangered species and only persists in a few fragmented populations, so populations would have to be relocated to an area within the butterfly’s range first before making use of the green roofs.

The study concluded that green roofs overall do provide important ecological and environmental benefits in the urban environment. It is also clear that green roofs support greater diversity than non-green roofs. However a policy shift towards replacing lost or declining habitats with poor-quality ones must be avoided. More research on the biodiversity of green roofs and the ecological interactions is required before policy action can maximise biodiversity gains.

Oberndorfer, E., Lundholm, J., Bass, B., Coffman, R. R., Doshi, H., Dunnett, N., … & Rowe, B. (2007). Green roofs as urban ecosystems: ecological structures, functions, and services. BioScience, 57(10), 823-833.
Williams, N. S., Lundholm, J., & MacIvor, J. S. (2014) Do green roofs help urban biodiversity conservation?. Journal of Applied Ecology. DOI: 10.1111/1365-2664.12333


Detecting invasive species: the case of the wood-boring beetle

wood boring beetle

Invasive species are mostly likely to invade an area through a port. We need a better understanding of the factors affecting their arrival and establishment if we are to detect them. Davide Rassati and colleagues from the university of of Padua in Legnaro, Italy, looked at how the port size and surrounding landscape (i.e. forests) influenced the occurrence of the wood-boring beetle, Cordylomera spinicornis.

At 15 Italian international ports, the surrounding forests and ports themselves were monitored using multi-funnel traps with bait. Both alien and native bark beetles (subfamily Scolytinae), longhorn beetles (family Cerambycidae) and jewel beetles (family Buprestidae) were found. Overall 14 alien species were found, 4 of which are new to Italy.

Alien species richness was positively correlated with imported commodities. However total forest cover near ports was positively correlated with the occurrence of native but not alien species. The alien and native species richness was higher in surrounding forests than the ports themselves.

Early detection of the invasive wood-boring beetles can be improved by identifying sites where the arrival and establishment of aliens is more probable, combined with an efficient trapping protocol. Ways to detect these insects include pheromone traps and encounter rate models (forecasts).

Byers, J. A., & Naranjo, S. E. (2014). Detection and monitoring of pink bollworm moths and invasive insects using pheromone traps and encounter rate models. Journal of Applied Ecology.
Rassati, D., Faccoli, M., Toffolo, E. P., Battisti, A., & Marini, L. (2014). Improving the early detection of alien wood‐boring beetles in ports and surrounding forests. Journal of Applied Ecology.