Summary Connectivity is regarded globally as a guiding principle for conservation planning, but due to difficulties in quantifying connectivity, empirical data remain scarce. Lack of meaningful connectivity metrics is likely leading to inadequate representation of important biological connections in reserve networks. Identifying patterns in landscape connectivity can, theoretically, improve the design of conservation areas. We used a network model to estimate seascape connectivity for coral reef‐associated fishes in a subtropical bay in Australia. The model accounted for two scales of connectivity: (i) within mosaics at a local scale and (ii) among these mosaics at a regional scale. Connections among mosaics were modelled using estimations of post‐larval small and intermediate movement distances represented by home ranges of two fish species. Modelled connectivity patterns were assessed with existing data on fish diversity. For fishes with intermediate home ranges (0–6 km), connectivity [quantified by the index Probability of Connectivity (dPC)] explained 51–60% of species diversity. At smaller home ranges (0–1 km), species diversity was associated closely with intramosaic connectivity quantified by the index dPCintra. Mosaics and their region‐wide connections were ranked for their contribution to overall seascape connectivity and compared against current positions and boundaries of reserves. Our matching shows that only three of the 10 most important mosaics are at least partly encompassed within a reserve, and only a single important regional connection lies within a reserve. Synthesis and applications. Notwithstanding its formal recognition in reserve planning, connectivity is rarely accounted for in practice, mainly because suitable metrics of connectivity are not available in planning phases. Here, we show how a network analysis can be effectively used in conservation planning by identifying biological connectivity inside and outside present reserve networks. Our results demonstrate clearly that connectivity is insufficiently represented within a reserve network. We also provide evidence of key pathways in need of protection to avoid nullifying the benefits of protecting key reefs. The guiding principle of protecting connections among habitats can be achieved more effectively in future, by formally incorporating our findings into the decision framework.
Living within planetary limits requires attention to justice as biophysical boundaries are not inherently just. Through collaboration between natural and social scientists, the Earth Commission defines and operationalizes Earth system justice to ensure that boundaries reduce harm, increase well-being, and reflect substantive and procedural justice. Such stringent boundaries may also affect 'just access' to food, water, energy and infrastructure. We show how boundaries may need to be adjusted to reduce harm and increase access, and challenge inequality to ensure a safe and just future for people, other species and the planet. Earth system justice may enable living justly within boundaries.Rapid Earth system changes in the Anthropocene are harming nature and humans. The Anthropocene is also marked by increasing inequalities 1 and vulnerabilities 2 . Scientists have proposed planetary boundaries, such as climate targets, to reduce global environmental risks. Within the Earth Commission, we aim to propose 'safe and just Earth system boundaries' (ESBs) that go beyond planetary boundaries as they also include a justice perspective and suggest transformations to achieve them 3 . Safe and just ESBs aim to stabilize the Earth system, protect species and ecosystems and avoid tipping points, as well as minimize 'significant harm' to people while ensuring access to resources for a dignified life and escape from poverty. If justice is not considered, the biophysical limits may not be adequate to protect current generations from significant harm. However, strict biophysical limits, such as reducing emissions or setting aside land for nature, can, for example, reduce access to food and land for vulnerable people, and should be complemented by fair sharing and management of the remaining ecological space on Earth 4 . Behavioural experiments show that people contribute to common pool resource stewardship if they see the process and outcomes as just 5 . This perspective offers an approach to Earth system justice (ESJ) that can guide and operationalize the identification of 'just ends' in terms of Earth system boundaries (ESBs) and access indicators, and 'just means' in terms of sustainability transformations. It provides a discursive shift to reframe environmental science and policy to pay attention to distributive justice 6 .
The Sustainable Development Goals aim to improve access to resources and services, reduce environmental degradation, eradicate poverty and reduce inequality. However, the magnitude of the environmental burden that would arise from meeting the needs of the poorest is under debate—especially when compared to much larger burdens from the rich. We show that the ‘Great Acceleration’ of human impacts was characterized by a ‘Great Inequality’ in using and damaging the environment. We then operationalize ‘just access’ to minimum energy, water, food and infrastructure. We show that achieving just access in 2018, with existing inequalities, technologies and behaviours, would have produced 2–26% additional impacts on the Earth’s natural systems of climate, water, land and nutrients—thus further crossing planetary boundaries. These hypothetical impacts, caused by about a third of humanity, equalled those caused by the wealthiest 1–4%. Technological and behavioural changes thus far, while important, did not deliver just access within a stable Earth system. Achieving these goals therefore calls for a radical redistribution of resources.
Predator–prey interactions are an inherently local‐scale phenomenon, but the intensity of these interactions can be mediated by abiotic conditions that can exert a multi‐scaled influence through space and time. Understanding how multi‐scale abiotic factors may influence local‐scale biotic processes has proven challenging; however, the hierarchical nature of riverine flow regimes makes these environments an ideal setting to test how predator–prey relationships may vary with multi‐scaled flow variation. We developed a series of Bayesian hierarchical models to explore how predator–prey relationships between barramundi Lates calcarifer and their prey may be influenced by multi‐scaled flow variables in the Daly River, northern Australia. We found that spatio‐temporal variation in barramundi abundance was strongly related to both antecedent flow and the abundance of prey fishes (predictive r2 = 0.57), and that barramundi abundance is more likely to be influenced by bottom‐up, rather than top‐down predator–prey dynamics. We also found that the strength and direction of these relationships varied across the catchment and between seasons. We found stronger, positive relationships between barramundi abundance and prey abundance in the most downstream sites with higher mean annual flows, compared to upstream sites. These results indicate that the abundance of predatory fishes can be related to both recent abiotic (flow) conditions and the abundance of prey (biotic conditions), and provides strong support for the importance of bottom‐up trophic dynamics. Management of iconic predators such as barramundi should therefore consider both flow management and other key factors such as habitat maintenance to support their prey.
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