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Item Open Access Growth and spectroscopy of lanthanide doped Y2SiO5 microcrystals for quantum information processing(Elsevier BV, 2023) Martin, Jamin; Williams LF; Reid, Michael; Wells, Jon-PaulLanthanide-doped Y2SiO5 microcrystals were prepared using the solution combustion, solid state and sol–gel synthesis techniques. Of these, the sol–gel method yields the most reliable and high-quality X2 phase Y2SiO5 microcrystals. Absorption and laser site-selective fluorescence measurements of Nd3+, Eu3+ and Er3+ doped material, performed at cryogenic temperatures, indicate that the as-grown microcrystals are of high optical quality with inhomogeneously broadened optical linewidths that are comparable to bulk crystals at similar dopant concentrations.Item Open Access Earthquake-induced habitat migration in a riparian spawning fish has implications for conservation management(Wiley, 2018) Orchard, Shane; Hickford, Michael; Schiel DRGalaxias maculatus is a riparian spawning fish that supports an important recreational fishery in New Zealand, with spawning habitat requirements strongly structured by salinity gradients at river mouths. This study reports changes to the spawning habitat following a series of large earthquakes that resulted in the widespread deformation of ground surfaces in the vicinity of waterways. Assessments of habitat recovery focused on two river systems, the Avon and Heathcote, with pre-disturbance data available over a 20-year period. Recovery dynamics were assessed by field survey and mapping of spawning habitat prior to and on seven occasions after the disturbance event. Riparian land-use and management patterns were mapped and analysed using overlay methods in a geographical information system (GIS). Habitat migration of up to 2 km occurred in comparison with all previous records, and several anthropogenic land uses have become threats because of changed patterns of co-occurrence. Incompatible activities now affect more than half of the spawning habitat in both rivers, particularly in areas managed for flood control purposes and recreational use. The results are an example of landscape-scale responses to salinity and water-level changes driven by tectonic dynamics. These dynamics are not the source of the stress per se; rather, they have increased the exposure of the species to pre-existing stressors. The case illustrates important principles for managing subtle, yet widespread, change. Adaptive conservation methods and investments in information are priorities for avoiding management failure following environmental change.Item Open Access Whitebait conservation and protected areas at non-tidal rivermouths: integrating biogeography and environmental controls on īnanga (Galaxias maculatus) spawning grounds(CSIRO Publishing, 2022) Orchard, Shane; Schiel, DGalaxias maculatus is a declining amphidromous fish that supports New Zealand's culturally important whitebait fisheries targeting the migratory juvenile stage. Spawning ground protection and rehabilitation is required to reverse historical degradation and improve fisheries prospects alongside conservation goals. Although spawning habitat has been characterised in tidal rivers, there has been no previous study of spawning in non-tidal rivermouths that are open to the sea. We assessed seven non-tidal rivers over 4 months using census surveys to quantify spawning activity, identify environmental cues, and characterise fundamental aspects of the biogeography of spawning grounds. Results include the identification of compact spawning reaches near the rivermouths. Spawning events were triggered by periods of elevated water levels that were often of very short duration, suggesting that potential lunar cues were less important, and that rapid fish movements had likely occurred within the catchment prior to spawning events. Spawning grounds exhibited consistent vertical structuring above typical low-flow levels, with associated horizontal translation away from the river channel leading to increased exposure to anthropogenic stressors and associated management implications for protecting the areas concerned. These consistent patterns provide a sound basis for advancing protective management at non-tidal rivermouths. Attention to flood management, vegetation control, and bankside recreational activities is needed and may be assisted by elucidating the biogeography of spawning grounds. The identification of rapid responses to environmental cues deserves further research to assess floodplain connectivity aspects that enable fish movements in ephemeral flowpaths, and as a confounding factor in commonly used fish survey techniques.Item Open Access Threshold Effects of Relative Sea-Level Change in Intertidal Ecosystems: Empirical Evidence from Earthquake-Induced Uplift on a Rocky Coast(MDPI AG, 2021) Orchard, Shane; Fischman HS; Gerrity S; Alestra T; Dunmore R; Schiel DRWidespread mortality of intertidal biota was observed following the 7.8 Mw Kaikōura earthquake in November 2016. To understand drivers of change and recovery in nearshore ecosystems, we quantified the variation in relative sea-level changes caused by tectonic uplift and evaluated their relationships with ecological impacts with a view to establishing the minimum threshold and overall extent of the major effects on rocky shores. Vertical displacement of contiguous 50 m shoreline sections was assessed using comparable LiDAR data to address initial and potential ongoing change across a 100 km study area. Co-seismic uplift accounted for the majority of relative sea-level change at most locations. Only small changes were detected beyond the initial earthquake event, but they included the weathering of reef platforms and accumulation of mobile gravels that continue to shape the coast. Intertidal vegetation losses were evident in equivalent intertidal zones at all uplifted sites despite considerable variation in the vertical displacement they experienced. Nine of ten uplifted sites suffered severe (>80%) loss in habitat-forming algae and included the lowest uplift values (0.6 m). These results show a functional threshold of c.1/4 of the tidal range above which major impacts were sustained. Evidently, compensatory recovery has not occurred—but more notably, previously subtidal algae that were uplifted into the low intertidal zone where they ought to persist (but did not) suggests additional post-disturbance adversities that have contributed to the overall effect. Continuing research will investigate differences in recovery trajectories across the affected area to identify factors and processes that will lead to the regeneration of ecosystems and resources.Item Open Access Drivers of participation in digital citizen science: Case studies on Järviwiki and safecast(Ubiquity Press, Ltd., 2020) Palacin V; Gilbert S; Orchard, Shane; Eaton A; Ferrario MA; Happonen ADigital citizen science platforms are prominent examples of modern volunteerism that provide people with opportunities to observe natural phenomena and to engage in scientific processes. In this study, we explore the values and motivations underlying sustained participation in digital citizen science projects through the lenses of two social psychology theories (Schwartz’s Human Values Theory and Self-Determination Theory). We present in-depth analyses of interviews with 15 long-term volunteers in two digital citizen science initiatives (Järviwiki and Safecast) that have been collecting environmental data for a decade in Finland and Japan. Our results advance the understanding of the values underpinning motivations. Our analyses show that openness-to-change values, such as self-direction, are important for initial participation, yet a diverse range of values, except for power, play a role in sustaining participation. Our study also shows that the values related to sustained participation are linked with extrinsic motivations, suggesting that when extrinsic motivators are self-directed, people will not only perform tasks willingly and enthusiastically but also in a sustained manner. Conceptualizing the behavioral continuum that drives volunteering actions provides practical insights that can assist the design, development, and evaluation of digital citizen science platforms.Item Open Access Allocations, quota and abalone fishery management: the Tragedy of the commons revisited(Informa UK Limited, 2023) Schiel DR; Gerrity S; Orchard, ShaneFisheries management uses a variety of methods to assess stocks, assign quota or allocations, and calculate potential for sustainability. In the New Zealand abalone (pāua) fishery, neither the total stocks nor amount removed in any fishing year are well-known because a major portion is fished ‘recreationally’, for which there is no requirement for a licence or catch reporting. Actual harvests relative to allocations cannot be established until well after the fishing season, and require data not typically collected. This was demonstrated over a 3-month fishing season opened after a 5-year closure along the earthquake-affected northeastern coast of the South Island. Recreational fishers removed c.74% of nearshore biomass of Haliotis iris populations. This was, in effect, a Tragedy of the Commons, whereby a common resource is exploited by those who harvest first, with scant regard for what remains. The underlying weakness is in the recreational fishing management rules which, in this instance, provide stark lessons in why abalone populations have come under pressure worldwide. We discuss concepts, prior knowledge, inertia in management, and a potential way forward, with the aim of preventing serial depletion of pāua populations and fostering more effective management that ends the Tragedy of the Commons.Item Open Access New Zealand Southern Alps Blanketed by Red Australian Dust During 2019/2020 Severe Bushfire and Dust Event(2024) Winton VHL; Charlier BLA; Purdie, Heather; Anderson B; Hunt JE; Dadic R; Taylor S; Petherick L; Novis PMEpisodic deposition of light absorbing impurities on glaciers reduces albedo and exacerbates snow melt. In 2019/2020 a devastating Australian bushfire and desert dust event combined with favorable meteorological conditions transported an unprecedented mass of impurities across the Tasman Sea turning the Southern Alps of Aotearoa New Zealand red. Here we use time lapse cameras, airmass back trajectories, snow impurity geochemistry, and remote sensing to quantify the timing, provenance, and mass deposition of the event. Deposited in late November 2019, the impurities were dominated by mineral dust with a distinct southeastern Australian geochemical fingerprint. The event deposited ∼4,500 ± 500 tons of red dust to Southern Alps permanent snow and ice with a mean dust mass concentration of 6.5 ± 0.7 g m− 2 . A southeast Australian desert dust storm generated by the same type of meteorological conditions as the 2020 New Year bushfires was the main driver of the glacier discoloration.Item Open Access A global review of legal protection mechanisms for the management of surf breaks(Elsevier BV, 2023) Orchard, Shane; Reiblich J; dos Santos MDLegal protection has become essential for managing the world's surf breaks much as it has for other marine and coastal protected areas. This paper presents the first systematic review of global developments in this field. We used a keyword literature search and thematic content analysis to characterise legal protection mechanisms that are designed for surf breaks or have been specifically applied to address surf break protection needs. They are currently found in six countries, protect over 500 surf breaks, and include examples of single-location mechanisms (e.g., Malibu in USA, Punta de Lobos in Chile) and national-level protection mechanisms addressing multiple surf breaks (e.g., New Zealand and Peru). Across all examples we identified 63 discrete themes that can be drawn upon to design and communicate protection measures and present these in a typology that highlights contributing ideas. Thematic analysis identified a major distinction between process and outcome-based requirements. More comprehensive protections can be recognised by attention to a wider range of threat classes and in the detail provided for decision support, with the two ideally working together to identify the minimum assessment requirements for development proposals. Variation in levels of protection is a key topic for consideration as is the process by which locations are identified or qualified for legal protections to apply. There is also a need to evaluate the effectiveness of provisions already in place, carrying with it the need for outcomes-based monitoring which is currently rare.Item Open Access Legal protection of New Zealand’s surf breaks: top-down and bottom-up aspects of a natural resource challenge(Informa UK Limited, 2020) Orchard, ShaneSurf breaks are natural resources that have experienced degradation in many countries worldwide. In response, protection initiatives have been established that are typically led by non-governmental groups. In 2010, New Zealand became the first country to establish legal protection for surf breaks at a national scale, as the result of a policy review. This article identifies contributions to these new developments with a focus on top-down and bottom-up activities that influenced the outcomes achieved. The substantive protection developments originated from the input of concerned individuals whose participation was not directly assured. These voluntary inputs were underpinned by a series of community-led activities that helped formulate and refine proposals to be put forward when the formal consultation opportunities arose. Although these bottom-up aspects had a strong influence on outcomes, top-down aspects of the context included decisions on the process adopted for policy review. This shaped the participation opportunities and therefore point of entry for bottom-up activities to engage. The case illustrates important principles for policy development where connections between top-down and bottom-up approaches are desired. Benefits include the potential for community-led solutions to natural resource challenges to be developed, and supported, as exemplified here.Item Open Access Cascading impacts of earthquakes and extreme heatwaves have destroyed populations of an iconic marine foundation species(Wiley, 2021) Thomsen, Mads; Mondardini L; Thoral F; Gerber D; Montie S; South PM; Tait, Leigh; Orchard, Shane; Alestra T; Schiel DR; Blakeslee AAim: Ecologists traditionally study how contemporary local processes, such as biological interactions and physical stressors, affect the distribution and abundance of organisms. By comparison, biogeographers study the distribution of the same organisms, but focus on historic, larger-scale processes that can cause mass mortalities, such as earthquakes. Here we document cascading effects of rare biogeographical (seismic) and more common ecological (temperature-related) processes on the distribution and abundances of coastal foundation species. Location: Intertidal wave-exposed rocky reefs around Kaikōura, New Zealand, dominated by large, long-lived, and iconic southern bull kelps (Durvillaea antarctica and Durvillaea willana). Methods: In November 2016, a 7.8 Mw earthquake uplifted the coastline around Kaikōura by up to 2 m, and a year later the region experienced the hottest summer on record. Extensive sampling of intertidal communities over 15 km coastline were done shortly after the earthquake and heatwaves and 4 years after the earthquake. Results: Durvillaea lost 75% of its canopy to uplift and the heatwaves reduced canopies that had survived the uplift by an additional 35%. The survey done 4 years after the earthquake showed that Durvillaea had not recovered and that the intertidal zone in many places now was dominated by small turfs and foliose seaweed. Main conclusions: Cascading impacts from seismic uplift and heatwaves have destroyed populations of Durvillaea around Kaikōura. Surviving smaller and sparser Durvillaea patches will likely compromise capacity for self-replacement and lower resilience to future stressors. These results are discussed in a global biogeographical-ecological context of seismic activity and extreme heatwaves and highlight that these events, which are not particularly rare in a geological context, may have common long-lasting ecological legacies.Item Open Access Hydrological modelling of niche construction at the Waitetoke Cultivation Complex, Ahuahu, Aotearoa New Zealand(Elsevier BV, 2024) Prebble, Matthew; Dijks A; Ladefoged TThe early Māori settlers of Ahuahu, a small island off the Coromandel Peninsula of Aotearoa New Zealand, engineered the environment to create a raised-bed irrigation system to grow taro (Colocasia esculenta). Three-dimensional computational fluid dynamic (CFD) modelling of water flow provides insights into how the irrigation system functioned. Excavation and coring data and a digital elevation model combine to simulate the hydrology of the raised-bed irrigation system at Waitetoke on Ahuahu. This modelling demonstrates that for operation, the system required a series of channels and weirs to divert water from a nearby spring. The slow-moving water delivered nutrients to the cultivation area and also promoted the growth of nitrogen fixing algae. Exogenous nutrients including wood ash and calcium carbonate along with fire modified rocks derived from nearby household hearths added to the cultivation matrix created ideal conditions for taro growth. Over the span of over two hundred years, Māori engaged in various forms of niche construction to enhance taro production by altering feedback relationships between the geomorphology of the area, a natural spring, the constructed channels and weirs, water, cultivars, algae, and soil nutrients.Item Open Access Are null segregants new combinations of heritable material and should they be regulated?(Frontiers Media SA, 2022) Heinemann JA; Clark K; Hiscox TC; McCabe AW; Agapito-Tenfen SZThrough genome editing and other techniques of gene technology, it is possible to create a class of organism called null segregants. These genetically modified organisms (GMOs) are products of gene technology but are argued to have no lingering vestige of the technology after the segregation of chromosomes or deletion of insertions. From that viewpoint regulations are redundant because any unique potential for the use of gene technology to cause harm has also been removed. We tackle this question of international interest by reviewing the early history of the purpose of gene technology regulation. The active ingredients of techniques used for guided mutagenesis, e.g., site-directed nucleases, such as CRISPR/Cas, are promoted for having a lower potential per reaction to create a hazard. However, others see this as a desirable industrial property of the reagents that will lead to genome editing being used more and nullifying the promised hazard mitigation. The contest between views revolves around whether regulations could alter the risks in the responsible use of gene technology. We conclude that gene technology, even when used to make null segregants, has characteristics that make regulation a reasonable option for mitigating potential harm. Those characteristics are that it allows people to create more harm faster, even if it creates benefits as well; the potential for harm increases with increased use of the technique, but safety does not; and regulations can control harm scaling.Item Open Access Missing the forest and the trees: Utility, limits and caveats for drone imaging of coastal marine ecosystems(MDPI AG, 2021) Tait , Leigh W.; Orchard, Shane; Schiel , David R.Coastal marine ecosystems are under stress, yet actionable information about the cumulative effects of human impacts has eluded ecologists. Habitat-forming seaweeds in temperate regions provide myriad irreplaceable ecosystem services, but they are increasingly at risk of local and regional extinction from extreme climatic events and the cumulative impacts of land-use change and extractive activities. Informing appropriate management strategies to reduce the impacts of stressors requires comprehensive knowledge of species diversity, abundance and distributions. Remote sensing un-doubtedly provides answers, but collecting imagery at appropriate resolution and spatial extent, and then accurately and precisely validating these datasets is not straightforward. Comprehensive and long-running monitoring of rocky reefs exist globally but are often limited to a small subset of reef platforms readily accessible to in-situ studies. Key vulnerable habitat-forming seaweeds are often not well-assessed by traditional in-situ methods, nor are they well-captured by passive remote sensing by satellites. Here we describe the utility of drone-based methods for monitoring and detecting key rocky intertidal habitat types, the limitations and caveats of these methods, and suggest a standardised workflow for achieving consistent results that will fulfil the needs of managers for conservation efforts.Item Open Access Negative resistance and resilience: Biotic mechanisms underpin delayed biological recovery in stream restoration(The Royal Society, 2021) Barrett , Isabelle C.; McIntosh, Angus; Febria , Catherine M.; Warburton, HelenTraditionally, resistance and resilience are associated with good ecological health, often underpinning restoration goals. However, degraded ecosystems can also be highly resistant and resilient, making restoration difficult: degraded communities often become dominated by hyper-tolerant species, preventing recolonization and resulting in low biodiversity and poor ecosystem function. Using streams as a model, we undertook a mesocosm experiment to test if degraded community presence hindered biological recovery. We established 12 mesocosms, simulating physically healthy streams. Degraded invertebrate communities were established in half, mimicking the post-restoration scenario of physical recovery without biological recovery. We then introduced a healthy colonist community to all mesocosms, testing if degraded community presence influenced healthy community establishment. Colonists established less readily in degraded community mesocosms, with larger decreases in abundance of sensitive taxa, likely driven by biotic interactions rather than abiotic constraints. Resource depletion by the degraded community likely increased competition, driving priority effects. Colonists left by drifting, but also by accelerating development, reducing time to emergence but sacrificing larger body size. Since degraded community presence prevented colonist establishment, our experiment suggests successful restoration must address both abiotic and biotic factors, especially those that reinforce the 'negative' resistance and resilience which perpetuate degraded communities and are typically overlooked.Item Open Access The dynamic threat from landslides following large continental earthquakes(2024) Arrell , Katherine; Rosser , Nick J.; Kincey , Mark E.; Robinson, Tom; Horton , Pascal; Densmore , Alex L.; Oven , Katie J.; Shrestha , Ram; Pujara, Dammar SinghEarthquake-triggered landslides show three important characteristics: they are often responsible for a considerable proportion of the damage sustained during mountain region earthquakes, they are non-randomly distributed across space, and they continue to evolve in the years after the earthquake. Despite this, planning for future earthquakes rarely takes into consideration either landslides or their evolution with time. Here we couple a unique timeseries of mapped landslides between 2014–2020 across the area of Nepal impacted by the 2015 Mw 7.8 Gorkha earthquake and a numerical landslide runout model overlain with building locations to examine how the distributions of both evolving landslide hazard and exposure intersect to generate a dynamic threat to buildings. The threat from landslide runout is shown to change in predictable ways after the earthquake, becoming more pronounced at mid- and lower-hillslope positions and remaining in the landscape for multiple years. Using the positions of our mapped landslides as a starting point, we can identify a priori the locations of 78% of buildings that were subsequently impacted by landslide debris. We show that landslide exposure and hazard vary from negligible to high, in relative terms, over lateral distances of as little as 10s of m. Our findings hold important implications for guiding reconstruction and for taking steps to reduce the risks from future earthquakes.Item Open Access Floristic homogenization of South Pacific islands commenced with human arrival(Springer Science and Business Media LLC, 2024) Strandberg NA; Steinbauer MJ; Walentowitz A; Gosling WD; Fall PL; Prebble, Matthew; Stevenson J; Wilmshurst JM; Sear DA; Langdon PG; Edwards ME; Nogué SThe increasing similarity of plant species composition among distinct areas is leading to the homogenization of ecosystems globally. Human actions such as ecosystem modification, the introduction of non-native plant species and the extinction or extirpation of endemic and native plant species are considered the main drivers of this trend. However, little is known about when floristic homogenization began or about pre-human patterns of floristic similarity. Here we investigate vegetation trends during the past 5,000 years across the tropical, sub-tropical and warm temperate South Pacific using fossil pollen records from 15 sites on 13 islands within the biogeographical realm of Oceania. The site comparisons show that floristic homogenization has increased over the past 5,000 years. Pairwise Bray–Curtis similarity results also show that when two islands were settled by people in a given time interval, their floristic similarity is greater than when one or neither of the islands were settled. Importantly, higher elevation sites, which are less likely to have experienced human impacts, tended to show less floristic homogenization. While biotic homogenization is often referred to as a contemporary issue, we have identified a much earlier trend, likely driven by human colonization of the islands and subsequent impacts.Item Open Access A Decision-Support Tool to Augment Global Mountain Protection and Conservation, including a Case Study from Western Himalaya(MDPI AG, 2023) Jacobs P; Carbutt C; Beever EA; Foggin JM; Martin M; Orchard, Shane; Sayre RMountains are remarkable storehouses of global biodiversity that provide a broad range of ecosystem services underpinning billions of livelihoods. The world’s network of protected areas includes many iconic mountain landscapes. However, only ca. 19% of mountain areas globally are protected (excluding Antarctica); many mountain areas are inadequately (<30% of their total terrestrial area) or completely unprotected. To support the UN Convention on Biological Diversity’s Global Biodiversity Framework goal of protecting at least 30% of the world’s lands by 2030, we have developed a strategic decision-support tool for identifying and prioritizing which candidate mountain areas most urgently require protection. To test its efficacy, we applied the tool to the Western Himalaya Case Study Area (WHCSA). The six-step algorithm harnesses multiple datasets including mountain Key Biodiversity Areas (KBAs), World Terrestrial Ecosystems, Biodiversity Hotspots, and Red List species and ecosystems. It also makes use of other key attributes including opportunities for disaster risk reduction, climate change adaptation, developing mountain tourism, maintaining elevational gradients and natural ecological corridors, and conserving flagship species. This method resulted in nine categories of potential action—four categories for follow-up action (ranked by order of importance and priority), and five categories requiring no further immediate action (either because countries are inadequately equipped to respond to protection deficits or because their KBAs are deemed adequately protected). An area-based analysis of the WHCSA identified 33 mountain KBAs regarded as inadequately protected, which included 29 inadequately protected World Mountain Ecosystems. All 33 inadequately protected KBAs in the WHCSA are Category A1: first-priority mountain KBAs (located in the Himalaya Biodiversity Hotspot in developing countries), requiring the most urgent attention for protection and conservation. Priorities for action can be fine-filtered by regional teams with sufficient local knowledge and country-specific values to finalize lists of priority mountain areas for protection. This rapid assessment tool ensures a repeatable, unbiased, and scientifically credible method for allocating resources and priorities to safeguard the world’s most biodiverse mountain areas facing myriad threats in the Anthropocene.Item Open Access "Blizzard blowing again and considerable discomfort on board as usual." Personal accounts of weather as scientific data, and the weather's influence on expedition members during the Heroic Age(Informa UK Limited, 2015) Rack, UrsulaThis paper presents an historic view on diaries and correspondence; in particular, how information related to weather was personally recorded and how Antarctic weather conditions influenced the expedition members in the Heroic Age (1897-1922). The paper is based on a presentation made at the Scientific Committee on Antarctic Research Open Science Conference in Auckland 2014. In this study, diaries have been used from the German “Gauss”-Expedition (also known as the “German South Polar Expedition”), led by Erich von Drygalski and the British “Discovery”-Expedition (also known as the “British National Antarctic Expedition”), led by Robert Falcon Scott. Both expeditions were undertaken during the period from 1901 through 1904. The timeframe is of particular interest, because it is a time when the men who went south did not have reliable comparative accounts in order to adequately mentally prepare for what they were about to experience. To put the research into a wider context, there are links drawn between otherItem Open Access Collective action problems led to the cultural transformation of Sāmoa 800 years ago(Public Library of Science (PLoS), 2024) Cochrane EE; Quintus S; Prebble, Matthew; Tautunu TAAM; Autufuga D; Laumea M; Queenin A; Augustinus P; Lincoln NK; Freeman JIn this research we identify the processes leading to hierarchical society in a region of Sāmoa, the often-labelled ‘birthplace’ of the Polynesian chiefdoms. Our analyses in the Falefa Valley on ‘Upolu island combine lidar mapping and ground survey to reveal an extensive system of archaeological features: rock walls, ditches, and platforms. Excavation and radiocarbon dating underpin a feature chronology and characterize feature variation. Soil nutrient analyses and geoarchaeological coring indicate spatial differences in the agricultural potentional of the valley and human modification of the environment over time. Our results demonstrate that the construction of large rock walls, some several hundred meters long, began approximately 900–600 years ago, shortly after rapid population rise in Sāmoa. This was followed by the building of small rock walls, often enclosing rectilinear fields or platforms. Both rock wall types are concentrated in the western and northern regions of the valley and greater rock wall densities are associated with areas of higher agricultural potential. The earliest wall construction was penecontemporaneous with partial forest removal that created a more productive wetland environment in the southeastern region of the valley, an area later a focus of agricultural ditching. We propose that with population rise the variable fertility of agricultural land became a significant resource gradient, influencing the population in two ways. First, areas of more fertile agricultural land promoted territorial behaviour, including large rock walls, and led to a collective action problem. Second, niche construction in the form of human-induced environmental change created a productive wetland agricultural system that was enhanced with a reticulate ditch network, the maintenance of which also led to a collective action problem. We conclude that in the Falefa Valley, the second largest catchment in Sāmoa, collective action problems were the cause of increased social hierarchy and may underlie the origins of chiefdoms throughout Polynesia.Item Open Access A demographic model to support customary management of a culturally important waterfowl species(Resilience Alliance, Inc., 2022) Herse MR; Lyver POB; Gormley AM; Scott NJ; McIntosh, Angus; Fletcher D; Tylianakis, JasonScientific support invited by Indigenous peoples and local communities (IPLC) to assist with customary environmental management can improve conservation and community livelihoods. For example, demographic models can help to understand how alternative wildlife management strategies affect population dynamics and harvest sustainability. We developed a demographic model to assist Ngāi Tahu, the southern-most Māori tribe in Aotearoa/New Zealand, in customary management of a culturally important population of Black Swans (kakī anau, Cygnus atratus). We used recent demographic data, including results of an experimental egg harvest study, to inform tangata tiaki (Ngāi Tahu environmental guardians) about how customary egg harvest and background pressure from sport hunting of swans aged ≥ 1 year differentially affect population growth. We also assessed how sport hunting of swans affects the sustainability of customary egg harvest. Estimated population growth (1.018 or presently growing 1.8% annually; 95% CI: 0.808– 1.241) was most sensitive to changes in adult and subadult survival, followed by juvenile (first-year) survival, breeding propensity, and nest hatching success. Uncertainty in population growth was almost entirely attributable to uncertainty in swan survival rates after hatching. Sustainable population-level rates of egg harvest varied from none to more than half of all eggs, depending on small changes in adult and subadult survival. Population sensitivity to adult and subadult survival suggests that limiting and monitoring their mortality are crucial to population and egg harvest sustainability, whereas contemporary government-mandated species management, through Fish and Game New Zealand, allows adult and subadult mortality from sport hunting, with little record of offtake. Recognizing the rights and interests of Ngāi Tahu, and monitoring swan mortality more closely, could improve Ngāi Tahu abilities to practice customary harvest, enhance population and environmental monitoring, and, when appropriate, control swan numbers in a culturally appropriate and less wasteful way. The model we present could aid decision making and communication between Ngāi Tahu and New Zealand’s Crown government within a potential future co-management arrangement. Demographic models can be useful tools for supporting customary environmental management, but developing, maintaining, and implementing these tools requires support for adaptive policies and management arrangements that recognize IPLC rights to the environment and decision making.