Integrating management of Pittosporum undulatum with other environmental weeds in Sydney's urban bushland

Abstract

Natural bushland is a dwindling resource in the Sydney Metropolitan Area, not only because of direct clearing, but also because uncontrolled impacts from surrounding development have caused increasing degradation over time. Community change has been characterized by invasions of environmental weeds, and consequent displacement of many indigenous species. A few locally native species, Pittosporum undulatum in particular, have emerged as environmental weeds. Invasion of new habitats within a species' natural geographic range must be recognized, since their impact on natural communities can be as serious as that of the worst exotic invaders. Factors implicated as the immediate cause of environmental weed invasions include increased human-induced dispersal by birds, anthropogenic disturbance, suppression of fire and increased moisture and nutrients. Management of plant invasions often includes mitigation to reduce impacts of the immediate causes. Strategies to maximize the success of mitigation by identifying and ameliorating the factors which impact bushland from remote sources are discussed. Practical recommendations for restoration of degraded sites are given. Native weeds such as P. undulatum require specialized treatment within an integrated environmental weed management strategy. It is stressed that application of the best management strategies available will be wasted if more fundamental issues related to current planning practices are ignored. Uncoordinated and ad hoc decisions are continuing to reduce urban bushland to mere remnants with high edge-to-interior ratios. Only when these practices are recognized and addressed can long-term success in the treatment of environmental weed invasions be achieved by the many excellent restoration techniques being developed.