Dian Spear

Global Biodiversity: Indicators of Recent Declines

Global Biodiversity Target Missed In 2002, the Convention on Biological Diversity (CBD) committed to a significant reduction in the rate of biodiversity loss by 2010. There has been widespread conjecture that this target has not been met. Butchart et al. (p. 1164, published online 29 April) analyzed over 30 indicators developed within the CBDs framework. These indicators include the condition or state of biodiversity (e.g., species numbers, population sizes), the pressures on biodiversity (e.g., deforestation), and the responses to maintain biodiversity (e.g., protected areas) and were assessed between about 1970 and 2005. Taken together, the results confirm that we have indeed failed to meet the 2010 targets. An analysis of 30 indicators shows that the Convention on Biological Diversity’s 2010 targets have not been met. In 2002, world leaders committed, through the Convention on Biological Diversity, to achieve a significant reduction in the rate of biodiversity loss by 2010. We compiled 31 indicators to report on progress toward this target. Most indicators of the state of biodiversity (covering species’ population trends, extinction risk, habitat extent and condition, and community composition) showed declines, with no significant recent reductions in rate, whereas indicators of pressures on biodiversity (including resource consumption, invasive alien species, nitrogen pollution, overexploitation, and climate change impacts) showed increases. Despite some local successes and increasing responses (including extent and biodiversity coverage of protected areas, sustainable forest management, policy responses to invasive alien species, and biodiversity-related aid), the rate of biodiversity loss does not appear to be slowing.

Uncertainty in invasive alien species listing

Lists of invasive alien species (IAS) are essential for preventing, controlling, and reporting on the state of biological invasions. However, these lists suffer from a range of errors, with serious consequences for their use in science, policy, and management. Here we (1) collated and classified errors in IAS listing using a taxonomy of uncertainty; and (2) estimated the size of these errors using data from a completed listing exercise, with the purpose of better understanding, communicating, and dealing with them. Ten errors were identified. Most result from a lack of knowledge or measurement error (epistemic uncertainty), although two were a result of context dependence and vagueness (linguistic uncertainty). Estimates of the size of the effects of these errors were substantial in a number of cases and unknown in others. Most errors, and those with the largest estimated effect, result in underestimates of IAS numbers. However, there are a number of errors where the size and direction of the effect remains poorly understood. The effect of differences in opinion between specialists is potentially large, particularly for data-poor taxa and regions, and does not have a clearly directional or consistent effect on the size and composition of IAS lists. Five tactics emerged as important for reducing uncertainty in IAS lists, and while uncertainty will never be removed entirely, these approaches will significantly improve the transparency, repeatability, and comparability of IAS lists. Understanding the errors and uncertainties that occur during the process of listing invasive species, as well as the potential size and nature of their effects on IAS lists, is key to improving the value of these lists for governments, management agencies, and conservationists. Such understanding is increasingly important given positive trends in biological invasion and the associated risks to biodiversity and biosecurity.

A standardized set of metrics to assess and monitor tree invasions

Abstract Scientists, managers, and policy-makers need functional and effective metrics to improve our understanding and management of biological invasions. Such metrics would help to assess progress towards management goals, increase compatibility across administrative borders, and facilitate comparisons between invasions. Here we outline key characteristics of tree invasions (status, abundance, spatial extent, and impact), discuss how each of these characteristics changes with time, and examine potential metrics to describe and monitor them. We recommend quantifying tree invasions using six metrics: (a) current status in the region; (b) potential status; (c) the number of foci requiring management; (d) area of occupancy (AOO) (i.e. compressed canopy area or net infestation); (e) extent of occurrence (EOO) (i.e. range size or gross infestation); and (f) observations of current and potential impact. We discuss how each metric can be parameterised (e.g. we include a practical method for classifying the current stage of invasion for trees following Blackburn’s unified framework for biological invasions); their potential management value (e.g. EOO provides an indication of the area over which management is needed); and how they can be used in concert (e.g. combining AOO and EOO can provide insights into invasion dynamics; and we use potential status and threat together to develop a simple risk analysis tool). Based on these metrics, we propose a standardized template for reporting tree invasions that we hope will facilitate cross-species and inter-regional comparisons. While we feel this represents a valuable step towards standardized reporting, there is an urgent need to develop more consistent metrics for impact and threat, and for many specific purposes additional metrics are still needed (e.g. detectability is required to assess the feasibility of eradication).

Animal introductions to southern systems: lessons for ecology and for policy

Numerous animal species have been introduced to areas from which they were previously absent, and many of these have become invasive, with substantial impacts. However, in other cases, impacts are assumed from theory. Empirical demonstrations are uncommon, making evidence-based conservation policy difficult to achieve. Here we review the broader ecological and conservation lessons from recent work on non-indigenous species in two southern systems, the policy implications thereof, and the subsequent changes to policy as a result of this work. First, we discuss invasions in the Antarctic region. Strong relationships exist between numbers of animal invasions and numbers of human visitors to Southern Ocean Islands, abiotic factors are often limiting for introduced species, homogenization across islands differs among taxonomic groups, and control actions can rapidly result in unintended consequences. This knowledge has influenced national policy and decisions within the Antarctic Treaty System. Second, we discuss ungulate introductions and translocations, both in South Africa and elsewhere. We show that substantial homogenization has resulted from both processes. However, firm evidence for impacts of ungulate introductions and translocations is sometimes difficult to find, despite the theoretical likelihood thereof. Such a lack of information may have profound consequences for the effective implementation of policy.