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The cascading effects of biodiversity decline on human well-being present a pressing challenge for sustainable development. Conservation efforts often prioritize safeguarding specific species, habitats, or intact ecosystems but overlook biodiversity's fundamental role in providing Nature's Contributions to People (NCP) in human -modified landscapes. Here, we systematically review 154 peer -reviewed studies to estimate the minimum levels of (semi -)natural habitat quantity, quality, and spatial configuration needed in human -modified landscapes to secure functional integrity essential for sustaining NCP provision. We find that the provision of multiple NCP is threatened when (semi -)natural habitat in the landscape falls below an area of 20%- 25% for each km2. Five NCP almost completely disappear below a level of 10% habitat. The exact quantity, quality, and spatial configuration of habitat required depends on local context and specific NCP. Today, about two-thirds of human -modified lands have insufficient (semi -)natural habitat, requiring action for NCP regeneration. Our findings serve as a generic guideline to target conservation actions outside natural areas.

The stability and resilience of the Earth system and human well-being are inseparably linked1,2,3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice)4. The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.

Critical water needs to sustain freshwater ecosystems and aquatic biodiversity in Queensland’s Mitchell River The Australian Government has identified water-resource development in the north of Australia as a priority for the coming years and Queensland’s Mitchell River is a focus of this interest. The Queensland Government currently regulates small amounts of extraction from the Mitchell River meaning that the flow regime is largely unregulated. In its current condition, the catchment supports existing water users, including Traditional Owners, and significant ecological assets, including wetlands of national significance, threatened species, traditional harvests, and commercial and recreational fisheries. Information is needed on the water needs of freshwater ecosystems and their associated biodiversity to guide decision-making around water planning and development. This project examined the links between freshwater flow and floodplain inundation, aquatic plant biomass accumulation, floodplain subsidies to freshwater food webs, fish movement and fisheries production. This project had five major objectives to understand the flow requirements of freshwater assets: 1. Identify the dependence of floodplain inundation and aquatic plant biomass accumulation on river flow 2. Map key ‘hotspots’ of freshwater primary productivity within the floodplain 3. Quantify riverine and floodplain connectivity to assess the likely impact of varying wet seasons and water-resource development on aquatic food webs, and the movement of fish between river channels and floodplain wetlands 4. Quantify the importance of river flows to estuaries by examining the flow dependence of barramundi growth, population dynamics and habitat use 5. Assess the implications of flow alteration on freshwater ecological communities, including movement of fish throughout the catchment.

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, The growing demand for freshwater resources has led to dam construction and water diversions in a majority of the world’s large rivers. The regulation of river flows, coupled with changes to land use in and around coastal areas, has far-reaching consequences not only for the ecology of rivers but also for fisheries in marine ecosystems. The challenges of quantifying the influence of regulated flows on marine fish stocks is complicated by our poor understanding of how flow induced processes interact over spatial and temporal scales throughout a species life history. The life history of the banana prawn, Penaeus merguiensis, is an ideal template to assess the potential impact of river regulation on the catch of a commercial fishery. The banana prawn is an estuarine-dependent marine species that spawn offshore and use estuaries as nursery areas. This research will ask how water resource development in three northern Australian rivers, the Mitchell, Gilbert and Flinders Rivers, affects population dynamics and catch of banana prawns in the south-eastern Gulf of Carpentaria. The extreme climatic variability in northern Australia raises concerns about how river regulation will impact marine fisheries. In Chapter 2, a spatio-temporal Bayesian modelwas developed to predict the impact of river regulation on the catch of banana prawns. The analyses of three river regulation scenarios found that catch was most impacted by river regulation during low flows. The impact of river regulation was greatest for a scenario with dams on the Mitchell River, where the model predicted catch would decline by 53% during a year with low flow. These results imply that maintenance of low-level flows is a crucial requirement for sustained fishery yields. Further, these findings suggest that water managers must balance the upstream demand for water during drier years against the impact on downstream prawn fisheries. Banana prawns have complex life histories where survival in the early life stages

Full Text, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Floodplains are highly productive and biodiverse ecosystems, and they provide many environmental services. Despite their importance, floodplains are under increasing pressure from human development and climate change. Worldwide, floodplains have witnessed those pressures translating into impacts that ultimately cause altered connectivity and impaired primary and secondary production. River floodplains in northern Australia are relatively intact compared to their counterparts in Australia, and play an important role in sustaining aquatic food webs. However, significant interest in agricultural expansion is being considered in northern Australia and the proposed intensive land and water resource development creates ecological concerns. The ecological functioning of those ecosystems relies on landscape connectivity and primary productivity. However, despite the importance of floodplain wetlands and the threats they face, a lack of information on those processes is apparent. The objective of this thesis is to develop a framework that accounts for primary production and connectivity in order to (a) inform river managers when identifying where to focus management and conservation efforts and (b) inform decision-makers in order to prioritise investment plans. Using the Mitchell River floodplain as a study area, I integrated field work, statistical models, remote sensing and graph theory to estimate rates of algal production and their statistical relationship to environmental features (Chapter 2); upscale those relationships across the landscape to identify hotspots of algal productivity (Chapter 3); and analyse connectivity across the Mitchell River floodplain and how water resources development can impact algal productivity and landscape connectivity (Chapter 4). The reason for focusing on algal production, especially epiphytic algae growing on aquatic macrophytes, is that this has been shown to be the major basal food resource for fish and other aquatic consumers in thes