936 research outputs found
Thermal limits to the geographic distributions of shallow-water marine species
No full textTemperature profoundly affects species’ geographic ranges, but the extent to which it limits contemporary range edges has been difficult to assess from laboratory experiments of thermal tolerance. The persistence of populations depends on temperature-mediated outcomes of ecological and demographic processes across all stages of a species’ life history, as well as any adaptation to local temperature regimes. We assessed the relationships between sea temperature and observed distributional ranges for 1,790 shallow-water marine species from 10 animal classes and found remarkable consistencies in trends in realized thermal limits among taxa and ocean basins, as well as general agreement with previous laboratory findings. Realized thermal niches increase from the Equator towards cold–temperate locations, despite an opposite trend in geographic range size. Species’ cool distribution limits are best predicted by the magnitude of seasonality within their range, while a relatively firm thermal barrier exists on the equatorward range edge for temperate species. Our findings of consistencies in realized thermal limits indicate potential limits to adaptation among common marine species and highlight the value of realized thermal niches for predicting species’ distributional dynamics in warming seas
Thermal biases and vulnerability to warming in the world’s marine fauna
No full textA critical assumption underlying projections of biodiversity change associated with global warming is that ecological communities comprise balanced mixes of warm-affinity and cool-affinity species which, on average, approximate local environmental temperatures. Nevertheless, here we find that most shallow water marine species occupy broad thermal distributions that are aggregated in either temperate or tropical realms. These distributional trends result in ocean-scale spatial thermal biases, where communities are dominated by species with warmer or cooler affinity than local environmental temperatures. We use community-level thermal deviations from local temperatures as a form of sensitivity to warming, and combine these with projected ocean warming data to predict warming-related loss of species from present-day communities over the next century. Large changes in local species composition appear likely, and proximity to thermal limits, as inferred from present-day species’ distributional ranges, outweighs spatial variation in warming rates in contributing to predicted rates of local species loss
Fishing-gear restrictions and biomass gains for coral reef fishes in marine protected areas
No full textConsiderable empirical evidence supports recovery of reef fish populations with fishery closures. In countries where full exclusion of people from fishing may be perceived as inequitable, fishing-gear restrictions on nonselective and destructive gears may offer socially relevant management alternatives to build recovery of fish biomass. Even so, few researchers have statistically compared the responses of tropical reef fisheries to alternative management strategies. We tested for the effects of fishery closures and fishing gear restrictions on tropical reef fish biomass at the community and family level. We conducted 1,396 underwater surveys at 617 unique sites across a spatial hierarchy within 22 global marine ecoregions that represented 5 realms. We compared total biomass across local fish assemblages and among 20 families of reef fishes inside marine protected areas (MPAs) with different fishing restrictions: no-take, hook-and-line fishing only, several fishing gears allowed, and sites open to all fishing gears. We included a further category representing remote sites, where fishing pressure is low. As expected, full fishery closures, (i.e., no-take zones) most benefited community- and family-level fish biomass in comparison with restrictions on fishing gears and openly fished sites. Although biomass responses to fishery closures were highly variable across families, some fishery targets (e.g., Carcharhinidae and Lutjanidae) responded positively to multiple restrictions on fishing gears (i.e., where gears other than hook and line were not permitted). Remoteness also positively affected the response of community-level fish biomass and many fish families. Our findings provide strong support for the role of fishing restrictions in building recovery of fish biomass and indicate important interactions among fishing-gear types that affect biomass of a diverse set of reef fish families.</p
Biological interactions both facilitate and resist climate-related functional change in temperate reef communities
No full textShifts in the abundance and location of species are restructuring life on the Earth, presenting the need to build resilience into our natural systems. Here, we tested if protection from fishing promotes community resilience in temperate reef communities undergoing rapid warming in Tasmania. Regardless of protection status, we detected a signature of warming in the brown macroalgae, invertebrates and fishes, through increases in the local richness and abundance of warm-affinity species. Even so, responses in protected communities diverged from exploited communities. At the local scale, the number of cool-affinity fishes and canopy-forming algal species increased following protection, even though the observation window fell within a period of warming. At the same time, exploited communities gained turf algal and sessile invertebrate species. We further found that the recovery of predator populations following protection leads to marked declines in mobile invertebrates—this trend could be incorrectly attributed to warming without contextual data quantifying community change across trophic levels. By comparing long-term change in exploited and protected reefs, we empirically demonstrate the role of biological interactions in both facilitating and resisting climate-related biodiversity change. We further highlight the potential for trophic interactions to alter the progression of both range expansions and contractions
New approaches to marine conservation through scaling up of ecological data
No full textIn an era of rapid global change, conservation managers urgently need improved tools to track and counter declining ecosystem conditions. This need is particularly acute in the marine realm, where threats are out of sight, inadequately mapped, cumulative, and often poorly understood, thereby generating impacts that are inefficiently managed. Recent advances in macroecology, statistical analysis, and the compilation of global data will play a central role in improving conservation outcomes, provided that global, regional, and local data streams can be integrated to produce locally relevant and interpretable outputs. Progress will be assisted by (a) expanded rollout of systematic surveys that quantify species patterns, including some carried out with help from citizen scientists; (b) coordinated experimental research networks that utilize large-scale manipulations to identify mechanisms underlying these patterns; (c) improved understanding of consequences of threats through the application of recently developed statistical techniques to analyze global species’ distributional data and associated environmental and socioeconomic factors; (d) development of reliable ecological indicators for accurate and comprehensible tracking of threats; and (e) improved data-handling and communication tools.<br/
Global conservation outcomes depend on marine protected areas with five key features
No full textIn line with global targets agreed under the Convention on Biological Diversity, the number of marine protected areas (MPAs) is increasing rapidly, yet socio-economic benefits generated by MPAs remain difficult to predict and under debate. MPAs often fail to reach their full potential as a consequence of factors such as illegal harvesting, regulations that legally allow detrimental harvesting, or emigration of animals outside boundaries because of continuous habitat or inadequate size of reserve. Here we show that the conservation benefits of 87 MPAs investigated worldwide increase exponentially with the accumulation of five key features: no take, well enforced, old (>10 years), large (>100km2), and isolated by deep water or sand. Using effective MPAs with four or five key features as an unfished standard, comparisons of underwater survey data from effective MPAs with predictions based on survey data from fished coasts indicate that total fish biomass has declined about two-thirds from historical baselines as a result of fishing. Effective MPAs also had twice as many large (>250mm total length) fish species per transect, five timesmore large fish biomass, and fourteen times more shark biomass than fished areas. Most (59%) of the MPAs studied had only one or two key features and were not ecologically distinguishable from fished sites. Our results show that global conservation targets based on area alone will not optimize protection of marine biodiversity. More emphasis is needed on better MPA design, durable management and compliance to ensure that MPAs achieve their desired conservation value.Fil: Graham, J. Edgar. University of Tasmania; AustraliaFil: Stuart Smith, Rick D.. University of Tasmania; AustraliaFil: Willis, Trevor J.. University of Portsmouth; Reino UnidoFil: Kininmonth, Stuart. University of Tasmania; Australia. Stockholms Universitet; SueciaFil: Baker, Susan C.. University of Tasmania; AustraliaFil: Banks, Stuart. Charles Darwin Foundation; EcuadorFil: Barrett, Neville S.. University of Tasmania; AustraliaFil: Becerro, Mikel A.. Natural Products and Agrobiology Institute; EspañaFil: Bernard, Anthony T. F.. South African Environmental Observation network; SudáfricaFil: Berkhout, Just. University of Tasmania; AustraliaFil: Buxton, Colin D.. University of Tasmania; AustraliaFil: Campbell, Stuart J.. Wildlife Conservation Society; Estados UnidosFil: Cooper, Antonia T.. University of Tasmania; AustraliaFil: Davey, Marlene. University of Tasmania; AustraliaFil: Edgar, Sophie C.. Department of Water; AustraliaFil: Försterra, Günter. Pontificia Universidad Católica de Valparaíso; ChileFil: Galvan, David Edgardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Irigoyen, Alejo Joaquin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; ArgentinaFil: Kushner, David J.. United States National Park Service; Estados UnidosFil: Moura, Rodrigo. Universidade Federal do Rio de Janeiro; BrasilFil: Parnell, P. Ed. University of California at San Diego. Scripps Institution of Oceanography; Estados UnidosFil: Shears, Nick T.. The University Of Auckland; Nueva ZelandaFil: Soler, German. University of Tasmania; AustraliaFil: Strain, Elisabeth M. A.. Universidad de Bologna; ItaliaFil: Thomson, Russell J.. University of Tasmania; Australi
Resilience and signatures of tropicalization in protected reef fish communities
No full textHabitat reserves can promote ecological resilience to climate variability by supporting intact trophic webs and large-bodied individuals1, 2, 3. Protection may also alter community responses to long-term climate change by offering habitat for range-shifting species4. Here we analyse the species richness, diversity and functional traits of temperate reef fish communities over 20 years in a global warming hotspot and compare patterns in a marine reserve with nearby sites open to fishing. Species richness and diversity oscillated strongly on the decadal scale. Long-term warming signatures were also present as increasing functional trait richness and functional diversity, driven in part by a general increase in herbivores. Nevertheless, reserve sites were distinguished from fished sites by displaying: greater stability in some aspects of biodiversity; recovery of large-bodied temperate species; resistance to colonization by subtropical vagrants; and less pronounced increases in the community-averaged temperature affinity. We empirically demonstrate that protection from fishing has buffered fluctuations in biodiversity and provided resistance to the initial stages of tropicalization
John Stuart Mill’s projected science of society: 1827-1848
No full textThe purpose of the thesis is to examine John Stuart Mill’s political thought from
about 1827 to 1848 as an exercise in intellectual history. It focuses, first, on Mill’s view,
formulated by the late 1830s, that contemporary society was ‘civilized’, and second, on
his project of a science of society, which he aspired to develop in the late 1830s and
early 1840s.
By the late 1830s, Mill came to the view that his contemporary society was a
‘commercial society or civilization’, dominated by the middle, commercial class. The
first part of my thesis, constituted by Chapters 2-4, discusses the way in which Mill
formed his notion of civilization, and what he meant by the term ‘civilization’. Mill paid
attention to the implications of the rise of the middle class, and regarded such
phenomena of contemporary society as the corruption of the commercial spirit and
excessive social conformity as an inevitable consequence of the rise of the middle class.
The second part of the thesis, constituted by Chapters 5-9, examines Mill’s
projected science of society. In the late 1830s and early 1840s, Mill attempted to
develop a new science of society whose subject-matter was the nature and prospects of
commercial, civilized society. This aspiration culminated in A System of Logic,
published in 1843. In examining Mill’s projected science, I pay particular attention to
the fact that he conceived new sciences of history and of the formation of character,
both of which were indispensable in his project, although he failed to give a complete
account of these sciences. My thesis shows that the implications of his interest both in
history and in the formation of character are more significant than Mill scholars have
assumed
Direct and indirect effects of heatwaves on a coral reef fishery
No full textMarine heatwaves are increasing in frequency and intensity, and indirectly impacting coral reef fisheries through bleaching-induced degradation of live coral habitats. Marine heatwaves also affect fish metabolism and catchability, but such direct effects of elevated temperatures on reef fisheries are largely unknown. We investigated direct and indirect effects of the devastating 2016 marine heatwave on the largest reef fishery operating along the Great Barrier Reef (GBR). We used a combination of fishery-independent underwater census data on coral trout biomass (Plectropomus and Variola spp.) and catch-per-unit-effort (CPUE) data from the commercial fishery to evaluate changes in the fishery resulting from the 2016 heatwave. The heatwave caused widespread, yet locally patchy, declines in coral cover, but we observed little effect of local coral loss on coral trout biomass. Instead, a pattern of decreasing biomass at northern sites and stable or increasing biomass at southern sites suggested a direct response of populations to the heatwave. Analysis of the fishery-independent data and CPUE found that in-water coral trout biomass estimates were positively related to CPUE, and that coral trout catch rates increased with warmer temperatures. Temperature effects on catch rates were consistent with the thermal affinities of the multiple species contributing to this fishery. Scaling-up the effect of temperature on coral trout catch rates across the region suggests that GBR-wide catches were 18% higher for a given level of effort during the heatwave year relative to catch rates under the mean temperatures in the preceding 6 years. These results highlight a potentially large effect of heatwaves on catch rates of reef fishes, independent of changes in reef habitats, that can add substantial uncertainty to estimates of stock trends inferred from fishery-dependent (CPUE) data. Overestimation of CPUE could initiate declines in reef fisheries that are currently fully exploited, and threaten sustainable management of reef stocks.Christopher J. Brown, Camille Mellin, Graham J. Edgar, Max D. Campbell, Rick D. Stuart‐Smit
Macroalgae and mobile reef invertebrates face high extinction risk
No full textIdentification of threatened species in the marine environment is hindered by high access costs and difficulties collecting population trend and geographical distribution data. These challenges have resulted in a poor coverage of marine species among assessments for the IUCN Red List of Threatened Species, reducing the potential value of the Red List for guiding conservation action in marine systems, including rocky and coral reefs. To quantify knowledge gaps in reef species threat assessments, we assessed population trends for 626 common shallow reef species at 869 sites around Australia from 1992 to 2024 using time series data from standardised ecological monitoring programs. A total of 82 of 229 species (36 %) with declining populations had rates of decadal decline that would qualify them as threatened based on Red List criteria. Over a third (38 %, n = 31/82) of these provisionally threatened species are endemic to the study region (Australia), with 5 currently listed as Least Concern and 26 Not Evaluated. Temperate macroalgae (12 species) and mobile macro-invertebrates (23 species: 14 Echinoderms, 8 Gastropods, 1 Malacostracan) are over-represented among provisionally threatened species and under-represented on the Red List. Expansion of monitoring and reporting programs, and more timely risk assessments that lead to improved management strategies, are required to better accommodate threats affecting speciose marine taxa, with the ultimate goal to allow proactive management, thereby reducing extinction risk.Olivia J. Johnson, Freddie J. Heather, Jemina Stuart-Smith, Rick D. Stuart-Smith, Camille Mellin, Graham J. Edga
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