Horizon scan for incoming weeds into Queensland, Australia

Invasive alien species (IAS), of which weeds are a subset, are often threats to natural and managed ecosystem services, including agriculture. The distribution and impacts of IAS are expected to exacerbate in response to increasing human connections (globalisation, commerce) and climate change. Unfortunately, once firmly established across large areas, populations of invasive species tend to become highly resilient and preventative measures become generally unaffordable or unrealistic. Hence, there is a need to identify emerging threats that are still in an early phase of invasion. These emerging threats can be candidates for preventative action; either complete eradication or early containment. Using the grey literature and the Web, including “The weed flora of Australia and its weed status” and “CABI’s invasive species compendium”, we carried out horizon scanning for ~230 weed species that have been identified as potential IAS in an early stage of invasion in Queensland (QLD), Australia. The majority of these potential IAS are of South and tropical North America in origin, and their present invaded ranges are wide (North/South America, Oceania, Asia, and Africa). Potential impacts are deemed generally negative (especially on environment/ecology, biodiversity, livestock, and economy/livelihood) to neutral, but positive impacts (on livestock, cultural amenity, and economy) were also identified. Introduction mode and pathways of entry are likely to be deliberate via nursery/horticultural trade (40 %), agroforestry for soil stabilization/habitat restoration (26 %) and mail-order/Internet (17.3 %). Once in their invaded ranges, further spread (dispersal) can be expected via mammals (especially by birds and rodents), soil disturbance/waste disposal and aquatic systems. Using the dataset on impact and spread of the focal IAS in invaded ranges around the globe and adjusting for countries/regions whose climates match closely to that of QLD, we derived a state-wide horizon weed priority list of high, medium and low impact scores for policy, research and management