Interaction of free-floating planets with a star-planet pair

The recent discovery of free-floating planets and their theoretical interpretation as celestial bodies, either condensed independently or ejected from parent stars in tight clusters, introduced an intriguing possibility. Namely, that some exoplanets are not condensed from the protoplanetary disk of their parent star. In this novel scenario a free-floating planet interacts with an already existing planetary system, created in a tight cluster, and is captured as a new planet. In the present work we study this interaction process by integrating trajectories of planet-sized bodies, which encounter a binary system consisting of a Jupiter-sized planet revolving around a Sun-like star. To simplify the problem we assume coplanar orbits for the bound and the free-floating planet and an initially parabolic orbit for the free-floating planet. By calculating the uncertainty exponent, a quantity that measures the dependence of the final state of the system on small changes of the initial conditions, we show that the interaction process is a fractal classical scattering. The uncertainty exponent is in the range (0.2-0.3) and is a decreasing function of time. In this way we see that the statistical approach we follow to tackle the problem is justified. The possible final outcomes of this interaction are only four, namely flyby, planet exchange, capture or disruption. We give the probability of each outcome as a function of the incoming planet's mass. We find that the probability of exchange or capture (in prograde as well as retrograde orbits and for very long times) is non-negligible, a fact that might explain the possible future observations of planetary systems with orbits that are either retrograde or tight and highly eccentric.Comment: 19 pages, 12 figure

Workshop to scope and preselect indicators for criterion D3C3 under MSFD decision (EU) 2017/848 (WKD3C3SCOPE)

The workshop to scope and preselect indicators for Descriptor 3 criterion 3 under MSFD Commission Decision (EU) 2017/848 (WKD3C3SCOPE) provided a platform for experts from the EU member states and relevant regional bodies to meet and support development and progress the assessment methodology, based on a request by the EC (DGENV). WKD3C3SCOPE is the first of a series of three workshops (WKD3C3THRESHOLDS and WKSIMULD3) to provide guidance in relation to operational indicators for MSFD D3C3. The workshop was organized as a series of presentations with intermittent group discussions. On the first day of the workshop the participants discussed what defines a ‘healthy population structure’ for species with different life history traits (ToR a). During the following days, the group discussed and identified relevant D3C3 indicators (ToR b) and developed criteria to select among the identified D3C3 indicators to allow further testing and setting of thresholds at WKD3C3THRESHOLDS (ToR c). The participants found that overall, healthy fish stocks are characterized by high productivity, wide age and size structuring in the population, and the ability to quickly recover from disturbances. The groups noted that environmental factors, along with stock biomass and fishing pressure, influence the productivity and health of a stock, with environment playing a particularly large role in the recruitment of short-lived stocks. It was suggested that the age structure of a stock might be more relevant for evaluating the health of long-lived stocks. However, it was acknowledged that not all stocks have sufficient data to evaluate all proposed indicators, and a single indicator is unlikely to suffice for all stocks. Data availability, species- specific factors and regional or sub-regional variation are thus also important considerations. In relation to ToR b, the participants presented their work on potential indicators including: recruitment time-series, proportion of fish larger than the mean size of first sexual maturation, F rec/Fbar, length distribution L 90, relative proportion of old fish above A 90, indicators of spawner quality, and SSB/R. A discussion on pros/cons, benefits to the population of high or low indicator values, benefits supported by empirical evidence, applicability to data-poor stocks and benefits supported by simulation/theoretical considerations followed the presentations. Finally, in relation to ToR c, the difficulty emerged in ranking the indicators alone without considering the data used to estimate them and a new set of evaluation criteria for use in WKD3C3THRESHOLDS were defined. Based on the outputs of the meeting a list of indicators to be further evaluated has been drafted, which also emphasizes the stocks for which studies have empirically demonstrated effects on productivity. In addition to the listed indicators, indicators of genetic diversity and proportion of fish with parasite infestation were mentioned but to the knowledge of the participants, widespread data for these are currently not publicly available.info:eu-repo/semantics/publishedVersio

Πρόβλεψη ρυθμών μείωσης βιοποικιλότητας που οφείλονται σε απώλεια ενδιαιτήματος

Biodiversity loss is accelerating as a result of the destruction of species natural habitats. Today there is no single framework for predicting the effects of habitat loss on biodiversity. However, the recent development of stochastic models of community assembly, in particular Hubbell’s neutral theory of biodiversity, gives the opportunity to model community dynamics. The purpose of this thesis is to investigate the capacity of the neutral model to describe the process of biodiversity decline following habitat loss (relaxation process), which we study in three applications of the model. First, the model is used to qualitatively describe the relaxation process in habitats that became isolated due to habitat loss. We estimate delayed extinctions as the difference between the species-area relationship (SAR), describing the habitat before the loss, and the isolate SAR, characterizing the remaining fragments, while both SARs are predicted from the model. Interestingly, delayed extinctions can be up to two orders of magnitude more than imminent extinctions. This shows the importance of including delayed extinctions in extinction forecasts, a fact that has been neglected in relevant studies. The second application deals with the problem of attribution of community temporal turnover to external drivers, like climate change; an observed turnover can be due to a systematic external driver or it can just be the result of natural drift (i.e. stochastic demography and random dispersal). Using the model, we estimated the expected (due to natural drift) temporal turnover of a community of butterflies. This is found to be less than the observed turnover. Still, a considerable amount of the observed turnover is explained by natural drift. This highlights the need for careful statistical tests before attributing observed alterations in communities to climate change, habitat loss or other external drivers. In the third application we present a mathematical description of the relaxation process. Solving the neutral model’s master equation, we derive a closed-form expression for the variation of species richness with time in a community that is subject to speciation. This is an extension of already existing results applying to completely isolated habitats. We used the equation to estimate relaxation times in islands and forest fragments that suffered habitat loss and found that the new formula improves the predictions. We conclude that the neutral model can provide a basis for a unified framework to describe the process of biodiversity loss.Η απώλεια ενδιαιτήματος αποτελεί σήμερα την κυριότερη αιτία εξαφάνισης ειδών. Ωστόσο, η πρόβλεψη των συνεπειών της απώλειας ενδιαιτήματος για τη βιοποικιλότητα δεν είναι εύκολη. Τα τελευταία χρόνια, η ανάπτυξη στοχαστικών μοντέλων οργάνωσης των βιοκοινοτήτων, όπως το ουδέτερο μοντέλο, έχει δώσει τη δυνατότητα να μελετηθεί η δυναμική των βιοκοινοτήτων. Στόχος της διατριβής είναι να διερευνηθεί η δυνατότητα του ουδέτερου μοντέλου να περιγράψει τη μείωση της βιοποικιλότητας που ακολουθεί την απώλεια ενδιαιτήματος, την οποία εξετάζουμε σε τρεις εφαρμογές του μοντέλου. Αρχικά κάνουμε μια ποιοτική περιγραφή της διαδικασίας των εξαφανίσεων. Το μοντέλο προβλέπει τις έμμεσες εξαφανίσεις (εξαφανίσεις που συμβαίνουν σε βάθος χρόνου μετά την απώλεια ενδιαιτήματος) ως τη διαφορά μεταξύ της σχέσης επιφάνειας-ειδών που περιγράφει το αρχικό ενδιαίτημα και της αντίστοιχης σχέσης που περιγράφει τα εναπομείναντα απομονωμένα ενδιαιτήματα, ενώ και οι δύο σχέσεις προκύπτουν από το μοντέλο. Όπως προκύπτει, οι έμμεσες εξαφανίσεις μπορεί να είναι τάξεις μεγέθους περισσότερες από τις ενδημικές. Παράλληλα με την απώλεια ενδιαιτήματος, η μεταβολή των κλιματικών συνθηκών μπορεί να αυξήσει τον ρυθμό εξαφάνισης ειδών. Ωστόσο η ανίχνευση των επιδράσεων της κλιματικής αλλαγής δεν είναι εύκολη, αφού οι κοινότητες μεταβάλλονται συνεχώς, χωρίς την επίδραση εξωτερικών παραγόντων, λόγω δημογραφικής στοχαστικότητας και διασποράς (φυσική διακύμανση). Στην δεύτερη εφαρμογή χρησιμοποιούμε το μοντέλο για να εκτιμήσουμε το μέγεθος της φυσικής διακύμανσης σε μια κοινότητα πεταλούδων. Βρήκαμε ότι η παρατηρούμενη διακύμανση είναι μεγαλύτερη από αυτήν που προβλέπεται λόγω φυσικής διακύμανσης. Παρόλα αυτά, η φυσική διακύμανση προκαλεί μεγάλη μεταβολή αφθονίας σε αρκετές περιπτώσεις. Αυτό τονίζει τη σημασία του στατιστικού ελέγχου για την εξαγωγή συμπερασμάτων σχετικά με τις παρατηρούμενες μεταβολές σε μια κοινότητα. Τέλος, χρησιμοποιούμε το μοντέλο για να προβλέψουμε την δυναμική της διαδικασίας των εξαφανίσεων. Με επίλυση της καταστατικής εξίσωσης του μοντέλου, διατυπώσαμε μια εξίσωση που περιγράφει τη μεταβολή του αριθμού ειδών με τον χρόνο σε μια κοινότητα που υπόκειται σε ειδογένεση. Η εξίσωση αποτελεί επέκταση αντίστοιχων λύσεων που αφορούν εντελώς απομονωμένες κοινότητες και βελτιώνει τις προβλέψεις για τον χαρακτηριστικό χρόνο ημιζωής της διαδικασίας. Καταλήγουμε ότι το ουδέτερο μοντέλο μπορεί να αποτελέσει βάση για την οικοδόμηση μιας ενοποιημένης περιγραφής της διαδικασίας των εξαφανίσεων που ακολουθεί την απώλεια ενδιαιτήματος

Future Socio-political Scenarios for Aquatic Resources in Europe : An Operationalized Framework for Marine Fisheries Projections

Climate change is anticipated to have long-term and widespread direct consequences for the European marine ecosystems and subsequently for the European fishery sector. Additionally, many socio-economic and political factors linked to climate change scenarios will impact the future development of fishing industries. Robust projection modeling of bioeconomic consequences of climate change on the European fishing sector must identify all these factors and their potential future interaction. In this study, four socio-political scenarios developed in the EU project CERES (Climate change and European aquatic RESources) were operationalized and used in model projections of marine wild capture fisheries. Four CERES scenarios (“World Markets,” “National Enterprise,” “Global Sustainability” and “Local Stewardship”) were based on the IPCC framework of Shared Socio-economic Pathways (SSPs). For each of these scenarios, a set of quantitative outputs was generated to allow projections of bio-economic impacts to mid-century (2050) on wild-capture fisheries operating in different European regions. Specifically, projections accounted for future changes in fisheries management targets, access regulations, international agreements, fish and fuel prices, technological developments and marine spatial planning. This study thoroughly describes the elements of these four fisheries scenarios and demonstrates an example of the “regionalization” of these scenarios by summarizing how they were applied to the North Sea flatfish fishery. Bioeconomic projections highlight the importance of future developments in fuel and fish price development to the viability of that and other fisheries. Adapting these scenarios for use in other models and regions outside the 10 European fisheries examined in CERES would be highly beneficial by allowing direct comparison of the bioeconomic risks and opportunities posed by climate change.</p

SEAwise Report on improved predictive models of recruitment under different environmental scenarios

This report investigates how key environmental variables influence the recruitment process of target fish stocks. Understanding how the environment affects recruitment may allow more accurate predictions of fish stock dynamics under scenarios of environmental change and in particular their response to global warming, supporting the development and implementation of robust management policies. Case studies from the four Seawise case study regions have been analysed, and the main results obtained so far are summarized below.In the Baltic Sea, the Gulf of Riga spring spawning herring showed effects of spawning stock biomass on individual weight of age-1 fish, with prey abundance in May and previous year feeding period temperature also playing significant roles. The explanatory power of the final model was moderate. Higher weight of herring is achieved at higher prey densities, lower SSB levels and lower temperatures during the main feeding season of age-0 fish. Recruitment of Western Baltic cod and herring showed decreasing reproductive potential at increasing temperature.In the North Sea, the effects of temperature, salinity, currents, chlorophyll and zooplankton on recruitment of cod, haddock, saithe, whiting, plaice, sole, sprat and herring were investigated using a semi-automated, machine learning framework. The incorporation of environmental signals in recruitment predictions showed improved predictions over a stock recruitment model without environmental effects in six out of the eight stocks. For small pelagic foirage fish, four stock-recruitment models were fitted for three sandeel stocks and the North Sea sprat stock Linear regressions revealed various relationships between recruitment and environmental variables. Short-term time scales based on monthly averages produced a noisier and less consistent pattern for most stock.In the Western Waters, Bayesian online change point detection models were applied to three Irish Sea stocks: Atlantic cod, whiting and common sole. Irish Sea cod recruitment was reduced at high sea surface temperatures and low copepod prey. Whiting and sole recruitment was less affected by environment but impacts for sole my occur in sole nursery areas. The Bay of Biscay anchovy recruitment was impacted by upwelling and turbulence whereas the Iberian sardine, productivity was low in the regime from 2006 onwards. Additional regime shifts for sardine were identified around 1993 and 2015. A numerical model was developed for European seabass simulating the impact of environmental factors on reproduction. The western channel sole recruitment is affected by spawning stock biomass and mean winter temperatures. The slightly closer link to Channel average temperatures rather than inshore site temperatures is consistent with temperature impacts directly on the survival rates of fish that were about to recruit.In the Mediterranean Sea, the influence of sea surface temperature, bottom temperature, salinity, bottom salinity and net primary production on recrutiment were investigated in the Adriatic and western Ionian Seas (GSAs17-18-19), and in most cases, these variables improved the predictive power. A study of the exchange of hake larvae and early juveniles between spawning grounds (the areas where adult hakes lay their eggs) and nurseries (where juveniles settle at the end of the larval phase) is still ongoing. In the Eastern Ionian Sea (GSA 20) improved predictive models of recruitment for European hake and red mullet incorporated environmental factors. Hake spawning stock biomass has a positive effect on recruitment up to a certain stock size but recruitment decreases at larger stock sizes. Recruitment is also influenced by microphytoplankton-related chlorophyll (chl4). Red mullet recruitment was also density dependent and influenced by chlorophyll-a and salinity

SEAwise Report on consistency of existing targets and limits for indicators in an ecosystem context

The SEAwise project works to deliver a fully operational tool that will allow fishers, managers, and policy makers to easily apply Ecosystem Based Fisheries Management (EBFM) in their fisheries. This SEAwise report investigates the consistency of existing targets and limits from the Common Fisheries Policy (CFP) and the Marine Strategy Framework Directive (MSFD). Trade-offs between different objectives (ecological, economic, social), targets and limits are highlighted. A wide range of model types (from bio-economic to full ecosystem models) has been applied to various case study areas accross the North East Atlantic and Mediterranean. Although model predictions are by nature uncertain, this study provides important information on likely inconsistencies between existing targets and limits and trade-offs expected under ecosystem- based fisheries management (EBFM). The scenarios investigated include the current range of management applied in terms of the Maximum Sustainable Yield (MSY) concept (i.e. strict MSY approach vs. Pretty Good Yield (PGY) approach allowing sustainable deviations from single species point estimates). The landing obligation is a key aspect of current fisheries management and was fully considered, in particular for mixed demersal fisheries.Maintaining current fishing effort without further management measures was the least sustainable option in nearly all cases studies. This approach led to increased risk of stocks falling below critical biomass limits. Although the fishing effort adaptions needed is highly case specific, this indicates that further management measures are likely to be needed to ensure a sustainable exploitation of all stocks.Scenarios applying a strict MSY approach in combination with the landing obligation as upper limit with fisheries ending when the first stock reaches in most case studies led to the lowest fishing effort. This had positive effects on MSFD related indicators such as bycatch of Protected, Endangered and Threatened (PET) species, benthic impact and the Large Fish Indicator as well as global indicators such as CO emission or ecosystem-based indicators like catch per . However, this scenario often led to the lowest catches from mixed demersal fisheries due to strong choke effects because fleets had to stop when their first quota was exhausted. This reduces social indicators such as food security, employment and wages. In terms of economic performance, the gains and loses were highly case specific. Scenarios applying the Pretty Good Yield concept and allowing sustainable deviations from the point estimate when stocks are in a healthy state often outperformed the scenarios applying as strict upper limit. Such scenarios, applying a more flexible interpretation of the MSY concept, led to reduced fishing effort compared to the status quo effort, but relaxed choke situations in mixed demersal fisheries to some extent leading to higher gross profits and in some case studies also to higher catches. Hence, they may constitute a compromise between the need to attain social as well as ecological objectives. Whether the associated effort levels lead to conflicts with MSFD objectives must be analysed when more internationally agreed thresholds become available for e.g., bycatch of PET species or benthic impact.The majority of case studies exceeded suggested thresholds for the global ecosystem indicators catch per km or primary production even under scenarios with high effort reductions. This can be explained to some extent by the fact that these indices are mainly driven by pelagic and industrial fisheries not always part of the models applied. Nevertheless, it indicates potential conflicts with such more holistic ecosystem indicators in their current form.Additional trade-offs in terms of yield were identified within the food web if e.g., demersal piscivorous predators feed on small pelagic fish and both groups are fished. Further, in case studies where small-scale fisheries (SSF) play an important role (e.g., Eastern Ionian Sea) additional trade-offs became apparent as different scenarios led to different ratios between revenues from small scale fisheries and revenues from large-scale fisheries. This adds another level of complexity when such aspects need to be taken more into account in future fisheries management under EBFM.The modelling assumed current selectivities and catchabilities will be maintained in the future. Especially trade-offs arising from fleets having to stop fishing when their first quota is exhausted or when e.g., a threshold for bycatch of PET species is reached may be resolved by improving selectivities via technical measures (e.g., closed areas or innovative gears) in the future. Deliverable 6.8 in month 36 will test such scenarios. Furthermore, the list of indicators and their targets and limits will be updated based on research within and outside SEAwise. Predictive capability of models will be enhanced by incorporating improved biological and economic sub-models in relation to environmental change. Climate change scenarios will be run and new harvest control rules (HCRs), proposed by SEAwise, will be tested. Finally, consistent targets and limits will be proposed for implementing EBFM

SEAwise Report on consistency of existing targets and limits for indicators in an ecosystem context

The SEAwise project works to deliver a fully operational tool that will allow fishers, managers, and policy makers to easily apply Ecosystem Based Fisheries Management (EBFM) in their fisheries. This SEAwise report investigates the consistency of existing targets and limits from the Common Fisheries Policy (CFP) and the Marine Strategy Framework Directive (MSFD). Trade-offs between different objectives (ecological, economic, social), targets and limits are highlighted. A wide range of model types (from bio-economic to full ecosystem models) has been applied to various case study areas across the North East Atlantic and Mediterranean. Although model predictions are by nature uncertain, this study provides important information on likely inconsistencies between existing targets and limits and trade-offs expected under ecosystem- based fisheries management (EBFM). The scenarios investigated include the current range of management applied in terms of the Maximum Sustainable Yield (MSY) concept (i.e. strict MSY approach vs. Pretty Good Yield (PGY) approach allowing sustainable deviations from single species FMSY point estimates). The landing obligation is a key aspect of current fisheries management and was fully considered, in particular for mixed demersal fisheries.Maintaining current fishing effort without further management measures was the least sustainable option in nearly all cases studies. This approach led to increased risk of stocks falling below critical biomass limits. Although the fishing effort adaptions needed is highly case specific, this indicates that further management measures are likely to be needed to ensure a sustainable exploitation of all stocks.Scenarios applying a strict MSY approach in combination with the landing obligation (i.e. FMSY as upper limit with fisheries ending when the first stock reaches FMSY) in most case studies led to the lowest fishing effort. This had positive effects on MSFD related indicators such as bycatch of Protected, Endangered and Threatened (PET) species, benthic impact and the Large Fish Indicator as well as global indicators such as CO2 emission or ecosystem-based indicators like catch per km2. However, this scenario often led to the lowest catches from mixed demersal fisheries due to strong choke effects because fleets had to stop when their first quota was exhausted. This reduces social indicators such as food security, employment and wages. In terms of economic performance, the gains and loses were highly case specific. Scenarios applying the Pretty Good Yield concept and allowing sustainable deviations from the FMSY point estimate when stocks are in a healthy state often outperformed the scenarios applying FMSY as strict upper limit. Such scenarios, applying a more flexible interpretation of the MSY concept, led to reduced fishing effort compared to the status quo effort, but relaxed choke situations in mixed demersal fisheries to some extent leading to higher gross profits and in some case studies also to higher catches. Hence, they may constitute a compromise between the need to attain social as well as ecological objectives. Whether the associated effort levels lead to conflicts with MSFD objectives must be analysed when more internationally agreed thresholds become available for e.g., bycatch of PET species or benthic impact.The majority of case studies exceeded suggested thresholds for the global ecosystem indicators catch per km2 or primary production even under scenarios with high effort reductions. This can be explained to some extent by the fact that these indices are mainly driven by pelagic and industrial fisheries not always part of the models applied. Nevertheless, it indicates potential conflicts with such more holistic ecosystem indicators in their current form.Additional trade-offs in terms of yield were identified within the food web if e.g., demersal piscivorous predators feed on small pelagic fish and both groups are fished. Further, in case studies where small-scale fisheries (SSF) play an important role (e.g., Eastern Ionian Sea) additional trade-offs became apparent as different scenarios led to different ratios between revenues from small scale fisheries and revenues from large-scale fisheries. This adds another level of complexity when such aspects need to be taken more into account in future fisheries management under EBFM.The modelling assumed current selectivities and catchabilities will be maintained in the future. Especially trade-offs arising from fleets having to stop fishing when their first quota is exhausted or when e.g., a threshold for bycatch of PET species is reached may be resolved by improving selectivities via technical measures (e.g., closed areas or innovative gears) in the future. Deliverable 6.8 in month 36 will test such scenarios. Furthermore, the list of indicators and their targets and limits will be updated based on research within and outside SEAwise. Predictive capability of models will be enhanced by incorporating improved biological and economic sub-models in relation to environmental change. Climate change scenarios will be run and new harvest control rules (HCRs), proposed by SEAwise, will be tested. Finally, consistent targets and limits will be proposed for implementing EBFM.</p