Anthropogenic trade and development have broken down dispersal barriers, facilitating the spread of diseases that threaten Earth’s biodiversity. We present a global, quantitative assessment of the amphibian chytridiomycosis panzootic, one of the most impactful examples of disease spread, and demonstrate its role in the decline of at least 501 amphibian species over the past half-century, including 90 presumed extinctions. The effects of chytridiomycosis have been greatest in large-bodied, range-restricted anurans in wet climates in the Americas and Australia. Declines peaked in the 1980s, and only 12% of declined species show signs of recovery, whereas 39% are experiencing ongoing decline. There is risk of further chytridiomycosis outbreaks in new areas. The chytridiomycosis panzootic represents the greatest recorded loss of biodiversity attributable to a disease.

Summary1. Large mammalian herbivores are major drivers of the structure and function of terrestrial ecosystems world-wide, and changes in their abundance have resulted in many populations being actively managed. Many empirical studies have identified that abundant mammalian herbivores can have negative impacts on biodiversity, but there has been no specific review of the impacts of native mammalian herbivores. 2. We assessed the peer-reviewed literature on the effects of large native herbivores on other animals. We aimed to quantitatively synthesize current knowledge, identify gaps and limitations in the literature, and highlight priorities for future research. 3. Most empirical studies of herbivory effects compared only two levels of herbivory (76%), and meta-analysis showed that very high densities of herbivores, when compared with very low densities, had mostly negative effects on other animal species. These negative effects were usually attributed to changes in the quantity and/or structure of vegetation. Only 24% of papers studied animal responses across a gradient of herbivore densities, and nonlinear responses to herbivory, as well as responses to low and moderate herbivore densities, remain poorly understood. 4. The literature also was dominated by short-term studies (76% sampled animal responses for 2 years or less), and there was a high incidence of confounding factors among studies (38% of studies). In addition, many studies used only coarse metrics to assess effects (e.g. only 33% of studies assessed species composition) and few included community-level synthesis (only 31% of studies reported results from more than one animal class). 5. Synthesis and applications. Critical questions remain for both basic ecology and the management of large native herbivores for biodiversity. Key knowledge gaps include (i) nonlinear responses to herbivore pressure, (ii) how responses differ between different herbivores, (iii) the spatial and (iv) the temporal variation of responses, (v) how the effects of herbivores interact with other land management activities and (vi) the mechanisms driving cascading effects through ecosystems. We identify ways to address these gaps and emphasize the need for studies which employ contrasts over a gradient of ecologically relevant herbivore densities and biologically meaningful time frames.

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Managing multiple, interacting disturbances is a key challenge to biodiversity conservation, and one that will only increase as global change drivers continue to alter disturbance regimes. Theoretical studies have highlighted the importance of a mechanistic understanding of stressor interactions for improving the prediction and management of interactive effects. However, many conservation studies are not designed or interpreted in the context of theory and instead focus on case-specific management questions. This is a problem as it means that few studies test the relationships highlighted in theoretical models as being important for ecological management. We explore the extent of this problem among studies of interacting disturbances by reviewing recent experimental studies of the interaction between fire and grazing in terrestrial ecosystems. Interactions between fire and grazing can occur via a number of pathways; one disturbance can modify the other's likelihood, intensity or spatial distribution, or one disturbance can alter the other's impacts on individual organisms. The strength of such interactions will vary depending on disturbance attributes (e.g. size or intensity), and this variation is likely to be nonlinear. We show that few experiments testing fire-grazing interactions are able to identify the mechanistic pathway driving an observed interaction, and most are unable to detect nonlinear effects. We demonstrate how these limitations compromise the ability of experimental studies to effectively inform ecological management. We propose a series of adjustments to the design of disturbance interaction experiments that would enable tests of key theoretical pathways and provide the deeper ecological understanding necessary for effective management. Such considerations are relevant to studies of a broad range of ecological interactions and are critical to informing the management of disturbance regimes in the context of accelerating global change.

The decomposition of animal biomass (carrion) contributes to the recycling of energy and nutrients through ecosystems. Whereas the role of plant decomposition in ecosystems is broadly recognised, the significance of carrion to ecosystem functioning remains poorly understood. Quantitative data on carrion biomass is severely lacking and there is no clear pathway towards improved knowledge in this area. Here we present a framework to show how quantities derived from individual carcasses can be scaled up using population metrics, allowing for comparisons among ecosystems and other forms of biomass. Our framework facilitates the generation of new data that is critical to building a quantitative understanding of carrion's contribution to trophic processes and ecosystem stocks and flows.

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Questions: Does browsing by large herbivores affect forest understorey diversity by modifying assemblage dominance? Does fire interact with browsing to affect forest understorey diversity? Does this interaction occur via a numerically mediated or functionally moderated pathway?Location: Booderee National Park, Jervis Bay Territory, south-eastern Australia. Methods:We tested the interactive effects of fire and browsing by native herbivores on understorey plant diversity using a randomized blocked experiment in an open eucalypt forest. We monitored the percentage cover of every vascular plant species in 24 sites over four experimental blocks. We applied a different treatment to each of the six sites in the four blocks. Treatments were a factorial combination of three levels of herbivory treatment (open, partial exclosure, full exclosure) and two levels of prescribed fire treatment (burned, unburned).Results: Browsing increased plant community dominance and reduced evenness and diversity, but only in burned sites. Heavy browsing following fire created an understorey dominated by an unpalatable, fire-resistant fern species (bracken, Pteridium esculentum). This fire-browsing interaction was driven by both numerically mediated and functionally moderated pathways: Fire both increased local browsing intensity, and amplified the per-unit effect of herbivores on the plant community. Conclusions:The altered competitive environment after fire, combined with heavy post-fire browsing created a depauperate understorey, dominated by bracken. The ability of bracken to suppress the establishment of other plants means that, once established, this fern-dominated understorey may be difficult to reverse. Our results demonstrate the key role of fire-browsing interactions in forest vegetation dynamics and highlight the importance of integrating large herbivore management with fire planning in forest ecosystems.