Current Constraints and Future Directions in Estimating Coextinction

Abstract: Coextinction is a poorly quantified phenomenon, but results of recent modeling suggest high losses to global biodiversity through the loss of dependent species when hosts go extinct. There are critical gaps in coextinction theory, and we outline these in a framework to direct future research toward more accurate estimates of coextinction rates. Specifically, the most critical priorities include acquisition of more accurate host data, including the threat status of host species; acquisition of data on the use of hosts by dependent species across a wide array of localities, habitats, and breadth of both hosts and dependents; development of models that incorporate correlates of nonrandom host and dependent extinctions, such as phylogeny and traits that increase extinction‐proneness; and determination of whether dependents are being lost before their hosts and adjusting models accordingly. Without synergistic development of better empirical data and more realistic models to estimate the number of cothreatened species and coextinction rates, the contribution of coextinction to global declines in biodiversity will remain unknown and unmanaged.     

Predictors of occupancy trend across spatial scale

Many explorations of extinction probability have had a global focus, yet it is unclear whether variables that explain the probability of extinction at large spatial extents are the same as those at small spatial extents. Thus, we used nearly annual presence-absence records for the most recent 40 years of a 110-year data set from Palenque, Mexico, an area with ongoing deforestation, to explore which of >200 species of birds have probabilities of extirpation that are likely to increase. We assessed associations between long-term trends in species presence (i.e., detection in a given year) and body size, geographic range size, diet, dependence on forest cover, taxonomy, and ecological specialization. Our response variable was the estimated slope of a weighted logistic regression for each species. We assessed the relative strength of each predictor by means of a model ranking scheme. Several variables associated with high extinction probability at global extents, such as large body size or small geographic range size, were not associated with occurrence of birds over time at our site. Body size was associated with species loss at Palenque, but occurrence trends of both very large and very small species, particularly the latter, have declined, or the species have been extirpated. We found no association between declining occurrence trend and geographic range size, yet decline correlated with whether a species depends on forest (mean occupancy trend =-0.0380, 0.0263, and 0.0186 for, respectively, species with high, intermediate, or low dependence on forest) and with complex combinations of diet and foraging strata (e.g., occurrence of canopy insectivores and terrestrial omnivores has increased, whereas occurrence of mid-level frugivores and terrestrial granivores has decreased). Our findings emphasize that analyses of local areas are necessary to explicate extirpation risk at various spatial extents.     

Proposed Definition of Environmental Damage Illustrated by the Cases of Genetically Modified Crops and Invasive Species

Abstract: The introduction of non‐native plant species and the release of genetically modified (GM) crops can induce environmental changes at gene to ecosystem levels. Regulatory frameworks such as the Convention on Biological Diversity or the EU Deliberate Release Directive aim to prevent environmental damage but do not define the term. Although ecologists and conservationists often refer to environmental effects of GM crops or invasive species as damage, most authors do not disclose their normative assumptions or explain why some environmental impacts are regarded as detrimental and others are not. Thus far, a concise definition of environmental damage is missing and is necessary for a transparent assessment of environmental effects or risks. Therefore, we suggest defining environmental damage as a significant adverse effect on a biotic or abiotic conservation resource (i.e., a biotic or abiotic natural resource that is protected by conservational or environmental legislation) that has an impact on the value of the conservation resource, the conservation resource as an ecosystem component, or the sustainable use of the conservation resource. This definition relies on three normative assumptions: only concrete effects on a conservation resource can be damages; only adverse effects that lead to a decrease in the value of the conservation resource can be damages; and only significant adverse effects constitute damage to a conservation resource. Applying this definition within the framework of environmental risk assessment requires further normative determinations, for example, selection of a threshold to distinguish between adverse and significant adverse effects and approaches for assessing the environmental value of conservation resources. Such determinations, however, are not part of the definition of environmental damage. Rather they are part of the definition's operationalization through assessment procedures, which must be grounded in a comprehensible definition of environmental damage.     

A Retrospective Evaluation of the Global Decline of Carnivores and Ungulates

Assessing temporal changes in species extinction risk is necessary for measuring conservation success or failure and for directing conservation resources toward species or regions that would benefit most. Yet, there is no long‐term picture of genuine change that allows one to associate species extinction risk trends with drivers of change or conservation actions. Through a review of 40 years of IUCN‐related literature sources on species conservation status (e.g., action plans, red‐data books), we assigned retrospective red‐list categories to the world's carnivores and ungulates (2 groups with relatively long generation times) to examine how their extinction risk has changed since the 1970s. We then aggregated species’ categories to calculate a global trend in their extinction risk over time. A decline in the conservation status of carnivores and ungulates was underway 40 years ago and has since accelerated. One quarter of all species (n = 498) moved one or more categories closer to extinction globally, while almost half of the species moved closer to extinction in Southeast Asia. The conservation status of some species improved (toward less threatened categories), but for each species that improved in status 8 deteriorated. The status of large‐bodied species, particularly those above 100 kg (including many iconic taxa), deteriorated significantly more than small‐bodied species (below 10 kg). The trends we found are likely related to geopolitical events (such as the collapse of Soviet Union), international regulations (such as CITES), shifting cultural values, and natural resource exploitation (e.g., in Southeast Asia). Retrospective assessments of global species extinction risk reduce the risk of a shifting baseline syndrome, which can affect decisions on the desirable conservation status of species. Such assessments can help conservationists identify which conservation policies and strategies are or are not helping safeguard biodiversity and thus can improve future strategies. Una Evaluación Retrospectiva de la Declinación Global de Carnívoros y Ungulados