RESUMEN

The coastal environment is not managed in a way that considers the impact of cumulative threats, despite being subject to threats from all realms (marine, land, and atmosphere). Relationships between threats and species are often nonlinear; thus, current (linear) approaches to estimating the impact of threats may be misleading. We developed a data-driven approach to assessing cumulative impacts on ecosystems and applied it to explore nonlinear relationships between threats and a temperate reef fish community. We used data on water quality, commercial fishing, climate change, and indicators of recreational fishing and urbanization to build a cumulative threat map of the northern region in New South Wales, Australia. We used statistical models of fish abundance to quantify associations among threats and biophysical covariates and predicted where cumulative impacts are likely to have the greatest impact on fish. We also assessed the performance of no-take zones (NTZs), to protect fish from cumulative threats across 2 marine protected area networks (marine parks). Fishing had a greater impact on fish than water quality threats (i.e., percent increase above the mean for invertivores was 337% when fishing was removed and was 11% above the mean when water quality was removed inside NTZs), and fishing outside NTZs affected fish abundances inside NTZs. Quantifying the spatial influence of multiple threats enables managers to understand the multitude of management actions required to address threats.

Una estrategia basada en datos para la evaluación de impacto de múltiples estresores en un área marina protegida Resumen Los ambientes costeros no se manejan de manera que se considere el impacto de las amenazas acumulativas, a pesar de que se enfrentan a amenazas de todos los entornos (marinas, terrestres y atmosféricas). Las relaciones entre las amenazas y las especies casi siempre son no lineales; por lo tanto, las estrategias actuales (lineales) para estimar el impacto de las amenazas pueden ser engañosas. Desarrollamos una estrategia basada en datos para evaluar el impacto acumulativo sobre los ecosistemas y la aplicamos para explorar las relaciones no lineales entre las amenazas y la comunidad de peces de arrecifes templados. Usamos datos de la calidad del agua, pesca comercial, cambio climático e indicadores de pesca recreativa y urbanización para construir un mapa acumulativo de amenazas de la región norte de Nueva Gales del Sur, Australia. Usamos modelos estadísticos de la abundancia de peces para cuantificar las asociaciones entre las amenazas y las covarianzas biofísicas y pronosticamos en dónde es probable que los impactos acumulativos sean mayores sobre los peces. También evaluamos el desempeño de las zonas de veda para así proteger a los peces de las amenazas acumulativas en dos redes de áreas marinas protegidas (parques marinos). La pesca tuvo un mayor impacto que la calidad del agua sobre los peces (es decir, el incremento del porcentaje por encima de la media de depredadores de invertebrados fue de 337% cuando se eliminó la pesca y fue de 11% por encima de la media cuando se eliminó la calidad del agua dentro de las zonas de veda) y la pesca fuera de las zonas de veda afectó la abundancia de los peces dentro de ellas. La cuantificación de la influencia espacial de las múltiples amenazas permite que los gestores entiendan la multitud de acciones de manejo que se requieren para abordar las amenazas.

Asunto(s)

RESUMEN

Both fire and predators have strong influences on the population dynamics and behaviour of animals, and the effects of predators may either be strengthened or weakened by fire. However, knowledge of how fire drives or mediates predator-prey interactions is fragmented and has not been synthesised. Here, we review and synthesise knowledge of how fire influences predator and prey behaviour and interactions. We develop a conceptual model based on predator-prey theory and empirical examples to address four key questions: (i) how and why do predators respond to fire; (ii) how and why does prey vulnerability change post-fire; (iii) what mechanisms do prey use to reduce predation risk post-fire; and (iv) what are the outcomes of predator-fire interactions for prey populations? We then discuss these findings in the context of wildlife conservation and ecosystem management before outlining priorities for future research. Fire-induced changes in vegetation structure, resource availability, and animal behaviour influence predator-prey encounter rates, the amount of time prey are vulnerable during an encounter, and the conditional probability of prey death given an encounter. How a predator responds to fire depends on fire characteristics (e.g. season, severity), their hunting behaviour (ambush or pursuit predator), movement behaviour, territoriality, and intra-guild dynamics. Prey species that rely on habitat structure for avoiding predation often experience increased predation rates and lower survival in recently burnt areas. By contrast, some prey species benefit from the opening up of habitat after fire because it makes it easier to detect predators and to modify their behaviour appropriately. Reduced prey body condition after fire can increase predation risk either through impaired ability to escape predators, or increased need to forage in risky areas due to being energetically stressed. To reduce risk of predation in the post-fire environment, prey may change their habitat use, increase sheltering behaviour, change their movement behaviour, or use camouflage through cryptic colouring and background matching. Field experiments and population viability modelling show instances where fire either amplifies or does not amplify the impacts of predators on prey populations, and vice versa. In some instances, intense and sustained post-fire predation may lead to local extinctions of prey populations. Human disruption of fire regimes is impacting faunal communities, with consequences for predator and prey behaviour and population dynamics. Key areas for future research include: capturing data continuously before, during and after fires; teasing out the relative importance of changes in visibility and shelter availability in different contexts; documenting changes in acoustic and olfactory cues for both predators and prey; addressing taxonomic and geographic biases in the literature; and predicting and testing how changes in fire-regime characteristics reshape predator-prey interactions. Understanding and managing the consequences for predator-prey communities will be critical for effective ecosystem management and species conservation in this era of global change.

Asunto(s)

RESUMEN

Data hungry, complex ecosystem models are often used to predict the consequences of threatened species management, including perverse outcomes. Unfortunately, this approach is impractical in many systems, which have insufficient data to parameterize ecosystem interactions or reliably calibrate or validate such models. Here we demonstrate a different approach, using a minimum realistic model to guide decisions in data- and resource-scarce systems. We illustrate our approach with a case-study in an invaded ecosystem from Christmas Island, Australia, where there are concerns that cat eradication to protect native species, including the red-tailed tropicbird, could release meso-predation by invasive rats. We use biophysical constraints (metabolic demand) and observable parameters (e.g. prey preferences) to assess the combined cat and rat abundances which would threaten the tropicbird population. We find that the population of tropicbirds cannot be sustained if predated by 1607 rats (95% credible interval (CI) [103, 5910]) in the absence of cats, or 21 cats (95% CI [2, 82]) in the absence of rats. For every cat removed from the island, the bird's net population growth rate improves, provided that the rats do not increase by more than 77 individuals (95% CI [30, 174]). Thus, in this context, one cat is equivalent to 30-174 rats. Our methods are especially useful for on-the-ground predator control in the absence of knowledge of predator-predator interactions, to assess whether 1) the current abundance of predators threatens the prey population of interest, 2) managing one predator species alone is sufficient to protect the prey species given potential release of another predator, and 3) control of multiple predator species is needed to meet the conservation goal. Our approach demonstrates how to use limited information for maximum value in data-poor systems, by shifting the focus from predicting future trajectories, to identifying conditions which threaten the conservation goal. This article is protected by copyright. All rights reserved.

RESUMEN

Our understanding on how organisms evolutionarily cope with simultaneously occurring, multiple threats over generations is still elusive. In a long-term experimental study, we therefore exposed clones of a freshwater cladoceran, Daphnia magna, to threats from predation and ultraviolet radiation (UVR) during three consecutive parthenogenetic generations. We show that Daphnia can adapt to different sets of threats within three generations through modifying morphology, swimming behavior, or life-history traits. When faced with predator cues, D. magna responded with reduced body size, whereas exposure to UVR induced behavioral tolerance when again exposed to this threat. Such UVR-tolerant behavior was initially associated with a reduced clutch size, but Daphnia restored the reproductive output gradually through generations. The findings advance our understanding on how those common invertebrates, with a global distribution, are able to persist and rapidly become successful in a changing environment.

Asunto(s)

RESUMEN

Global conservation promotes solutions to different dimensions of threat and response: land-use change, climate change, pollution, and so forth. Countering each threat has its band of proponents who advocate for their cause as paramount, increasingly, given limited resources, by downplaying the relative importance of others. Not only does this encourage a compartmentalised view of the world, which is ecologically unsound, it allows politicians and others to cherry-pick responses in light of political expediency or local demands. We should instead aim to achieve win-win conservation strategies that address multiple threats to diversity acting at different timescales, as well as 'horizon threats', which occur at large scales and may be the most challenging conservation issues to address in both the present and the future.

Asunto(s)

RESUMEN

Coastal tourism is a growing industry sector in the Mediterranean Basin. This and the other human activities occurring along the coastline share space and resources, leading to conflicts for divergent uses. Moreover, the overexploitation of natural resources degrades and depletes coastal habitats, with negative feedback effects for all human activities. Hence, both tourism and the other human activities have to consider their dependence on coastal ecosystem services, and act at technical and policy level to reach a compromise that preserves natural resources in the long term. Here we provide a conceptual framework illustrating the complex relationships and trade-offs among threats from coastal tourism and from other human activities and coastal ecosystem services, with a focus on cultural ones. We discuss the negative feedbacks on tourism development and provide examples of geospatial analysis on cumulative threats generated by other human activities and affecting tourism itself. The proposed conceptual framework and the threat analysis aim at highlighting the negative feedback effects of human driven threats on the development of Mediterranean coastal tourism, through an ecosystem service perspective. Both tools provide valuable insight for supporting decision makers and planners in achieving integrated coastal management, with a focus on sustainable tourism.

RESUMEN

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components' vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions.

Hacia un Marco de Trabajo para la Evaluación y el Manejo de los Impactos Humanos Acumulativos sobre las Redes Alimenticias Marinas Resumen El manejo efectivo con base en los ecosistemas requiere entender la respuesta de los ecosistemas a múltiples amenazas humanas en lugar de enfocarse en amenazas individuales. Para entender holísticamente la respuesta de los ecosistemas a las múltiples amenazas antropogénicas es necesario saber cómo estas amenazas afectan a los diferentes componentes dentro de los ecosistemas y cómo alteran finalmente el funcionamiento de los ecosistemas. Usamos el estudio de caso de la red alimenticia del pasto marino del Mediterráneo (Posidonia oceanica) y la obtención de conocimiento de expertos en una aplicación de los pasos iniciales de un método para la evaluación de los impactos humanos acumulativos sobre las redes alimenticias. Produjimos un modelo de red alimenticia de pastos marinos, determinamos las principales relaciones tróficas, identificamos a las principales amenazas para los componentes de la red y evaluamos la vulnerabilidad de los componentes a esas amenazas. Algunas amenazas tuvieron impactos altos (p. ej.: infraestructura costera) o bajos (p. ej.: escorrentía agrícola) sobre todos los componentes de la red, mientras que otros (p. ej.: carnívoros introducidos) tuvieron impactos muy diferentes sobre cada componente. Partir al ecosistema en sus componentes nos permitió identificar amenazas no vistas previamente y reevaluar la importancia de las amenazas percibidas comúnmente como mayores. Al incorporar este entendimiento de la vulnerabilidad del sistema con datos sobre los cambios en el estado de cada amenaza (p. ej.: disminución de la contaminación doméstica e incremento de la pesca) al modelo de red alimenticia, los manejadores pueden ser capaces de estimar y predecir de mejor manera los impactos humanos acumulativos sobre los ecosistemas y priorizar las acciones de conservación.

Asunto(s)