The risk posed by invasive alien species is determined primarily by two factors: distribution (occupancy) and abundance (density). However, most ecological studies use distribution data for monitoring and assessment programs, but few incorporate abundance data due to financial and logistical constraints. Failure to take into account invaders’ abundance may lead to imprecise pest risk assessments. Since 2003 as part of the Annual Pest Distribution Survey (APDS) exercise in the state of Queensland, Australia, government biosecurity officials have collected data on distribution and abundance of more than 100 established and emerging weeds. This data acquisition was done at spatial grid sizes of 17–50 × 17–50 km and across a very broad and varied geographical land area of ~2 × 106 km2. The datasets provide an opportunity to compare weed dynamics at large-medium spatial scales. Analysis of the APDS datasets indicated that weed distributions were highest in regions along the southern and central, coastal parts of Queensland, and decreased in the less populated inland (i.e. western) and northern parts of the state. Weed abundance showed no discernible landscape or regional trends. Positive distribution–abundance relationships were also detected at multiple spatial scales. Using both traits of weed abundance and distribution, we derived a measure of invasion severity, and constructed, for several (64) weed species, ‘space-for-time’ invasion curves. State-wide and in each of Queensland’s 10 regions, we also categorised the invasion stages of these weeds. At the grassroots of local government area or regional levels, the derived invasion curves and stage categories can provide policy direction for long-term management planning of Queensland’s priority weeds.
Nature conservation is underresourced, requiring managers to prioritize where, when, and how to spend limited funds. Prioritization methods identify the subset of actions that provide the most benefit to an actor's objective. However, spending decisions by conservation actors are often misaligned with their objectives. Although this misalignment is frequently attributed to poor choices by the actors, we argue that it can also be a byproduct of working alongside other organizations. Using strategic analyses of multi-actor systems in conservation, we show how interactions among multiple conservation actors can create misalignment between the spending and objectives of individual actors and why current uncoordinated prioritizations lead to fewer conservation objectives achieved for individual actors. We draw three conclusions from our results. First, that misalignment is an unsuitable metric for evaluating spending, because it may be necessary to achieve actors’ objectives. Second, that current prioritization methods cannot identify optimal decisions (as they purport to do), because they do not incorporate other actors’ decisions. Third, that practical steps can be taken to move actors in the direction of coordination and thereby better achieve their conservation objectives.
Shrubs are an important component of vegetation throughout the world. They are particularly significant in semiarid environments where they can dominate, driving ecosystem structure and functioning, and shaping land use. Life-history information was derived for Eremophila sturtii R.Br. and Dodonaea viscosa subsp. angustissima J.G.West, two widespread and common shrubs of semiarid eastern Australia. Plants growing under background climatic conditions took between 2 and 4 years to become established, attained the capacity to reproduce sexually at between 10 and 12 years, were in a sexually reproductive stage for between 17 and 28 years and lived an average maximum of 33–40 years. Under background climatic conditions between 70 and 80% of plants that entered the juvenile stage survived to sexual maturity while under severe drought this proportion fell to between 40 and 60%. Juvenile plants, particularly of E. sturtii, experienced the highest mortality under background conditions while, when exposed to severe drought, older plants, particularly D. viscosa subsp. angustissima in the intermediate stage, experienced the greatest increase in mortality, dying at more than twice the background rate. The high survival rates of E. sturtii and D. viscosa subsp. angustissima shown here, even under extreme drought conditions and in grazed- and ungrazed areas, help to explain why these shrub species have been observed to dominate vegetation in large areas of eastern Australia.
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