Donna Clarke

Management of powerline corridors in Australia has traditionally focused on the complete removal of vegetation using short rotation times owing to the perceived hazard of fire associated with corridor vegetation. Because of the intense management associated with fire hazards, little thought has been given to use of powerline corridors by wildlife. This has resulted in corridors traditionally being viewed as a source of fragmentation and habitat loss within forested ecosystems. We investigated the responses of small mammal communities living in a powerline corridor to management-induced vegetation changes at different successional stages, to determine whether a compromise could be reached between managing corridors for fire and biodiversity. Habitat modelling in the corridor and adjacent forest for three native and one introduced small mammal species demonstrated that species responded to changes in vegetation structural complexity, rather than time-since-management per se. Early seral stages of vegetation recovery after corridor management encouraged the introduced house mouse (Mus domesticus) into corridors and contributed little to biodiversity. Mid-seral-stage vegetation, however, provided habitat for native species that were rare in adjacent forest habitats. As the structural complexity of the vegetation increased, the small mammal community became similar to that of the forest so that corridor vegetation contributed fewer biodiversity benefits while posing an unacceptable fire risk. If ecologically sensitive management regimes are implemented to encourage mid-seral vegetation and avoid complete vegetation removal, powerline corridors have the potential to improve biodiversity. This would maintain landscape connectivity and provide habitat for native species uncommon in the forest while still limiting fuel loads in the corridor.

Within Australia, very little attention has been given to the potential biodiversity benefits of powerline easements, if ecologically sensitive management regimes are developed. This study examined the potential powerline easements may have for the conservation of small mammals, and in particular the near threatened, Broad-toothed Rat Mastacomys fuscus, in Australia. Easement vegetation was found to support a diverse small mammal community, including M. fuscus if the vegetation was allowed to develop some structural complexity. M. fuscus was one of the first species to recolonize the easement habitat, provided that the areas had regenerated to a sufficient level. Results suggests however that the current management technique used, where the entire easement is managed at one time via mass slashing, on short rotation times, is most likely limiting M. fuscus to low abundances, and causing isolation of the current M. fuscus populations. To ensure that powerline easements supply functional, usable habitat for small mammals and other species and to minimize their potential to fragment small mammal populations, it is recommended that current management techniques be reassessed. In an effort to develop more appropriate management regimes, it was recommended that rotation times be increased between management, that mass slashing of the easement at one time be reassessed, especially in naturally low growing areas and that rotational type slashing be implemented. Other techniques such as spot spraying, may be all that is needed within some areas to control emergent saplings. This study highlights that potential biodiversity values do exist for Australian powerline easements, if some changes occur to the current management practices.

Powerline corridors through forested ecosystems have been criticised due their potential to fragment the landscape and facilitate the intrusion of undesirable species into natural areas. This study investigates the effects of vegetation management (slashing), on: (1) timing of small mammal recolonisation; (2) vegetation characteristics that drive small mammal responses; and (3) the point where corridor resources are sufficient to provide functional habitat for native species. Small mammal trappingwas undertaken within Bunyip State Park, Australia, across three sites, once a month from January 2001 to May 2002 and every 2 months thereafter until January 2004. Changes in vegetation around each trap station were assessed annually in the forest and bi-annually in the corridor. Principal components analysis on the vegetation structural complexity values produced factors for use in species abundance models.Native small mammal species recolonised the corridor 1.5–3.5 years after management and the corridor supported a breeding population of small mammals around 2.5 years post-management. Males however, generally recolonised the corridor first, resulting in a sex-biased population in these areas. Species corridor habitat models for five native and one introduced species suggested cover and shelter were more important in determining corridor use than plant species per se. Powerline corridors have the potential to create a mixture of different successional stages, enhancing habitat availability for many species. However, the intensity of current management needs to be reduced and an integrated approach to management needs to be undertaken if
powerline corridors are to continuously provide habitat for native small mammal species.

Powerline corridor management in Australia has traditionally focused on the complete removal of vegetation using short rotation times due to the perceived fire hazard associated with corridor vegetation. This study assessed vegetation recovery in a powerline corridor, following management, at three sites
spanning corridor and forest habitat. Forest and corridor vegetation communities differed significantly between sites and over time. As vegetation recovered, the corridor community became a mix of plants common in the surrounding forest and open areas, changing within the 3-year study from a grass–fern to shrub–sedge community encroached by midstorey species. The current short rotations between management events unnecessarily maintain the corridor in a cycle of degradation, remove resources for native species and may allow introduced grasses and saplings to proliferate in the corridor. Maintaining a shrub layer would help avoid loss of species richness, encourage native species and limit colonisation opportunities of introduced species. Spot spraying emergent saplings and problem plants and mosaic slashing, would keep fire risk low and maintain biodiversity without increasing biomass to dangerous levels.

Background: This work explores the potential contribution of bioenergy technologies to 60% and 80% carbon reductions in the UK energy system by 2050, by outlining the potential for accelerated technological development of bioenergy chains. The investigation was based on insights from MARKAL modelling, detailed literature reviews and expert consultations. Due to the number and complexity of bioenergy pathways and technologies in the model, three chains and two underpinning technologies were selected for detailed investigation: (1) lignocellulosic hydrolysis for the production of bioethanol, (2) gasification technologies for heat and power, (3) fast pyrolysis of biomass for bio-oil production, (4) biotechnological advances for second generation bioenergy crops, and (5) the development of agro-machinery for growing and harvesting bioenergy crops. Detailed literature searches and expert consultations (looking inter alia at research and development needs and economic projections) led to the development of an 'accelerated' dataset of modelling parameters for each of the selected bioenergy pathways, which were included in five different scenario runs with UK-MARKAL (MED). The results of the 'accelerated runs' were compared with a low-carbon (LC-Core) scenario, which assesses the cheapest way to decarbonise the energy sector.

Results: Bioenergy was deployed in larger quantities in the bioenergy accelerated technological development scenario compared with the LC-Core scenario. In the electricity sector, solid biomass was highly utilised for energy crop gasification, displacing some deployment of wind power, and nuclear and marine to a lesser extent. Solid biomass was also deployed for heat in the residential sector from 2040 in much higher quantities in the bioenergy accelerated technological development scenario compared with LC-Core. Although lignocellulosic ethanol increased, overall ethanol decreased in the transport sector in the bioenergy accelerated technological development scenario due to a reduction in ethanol produced from wheat.

Conclusion: There is much potential for future deployment of bioenergy technologies to decarbonise the energy sector. However, future deployment is dependent on many different factors including investment and efforts towards research and development needs, carbon reduction targets and the ability to compete with other low carbon technologies as they become deployed. All bioenergy technologies should become increasingly more economically competitive with fossil-based technologies as feedstock costs and flexibility are reduced in line with technological advances.