From virtually extinct to superabundant in 35 years: establishment, population growth and shifts in management focus of the Swedish wild boar (Sus scrofa) population

Background The wild boar (Sus scrofa) was extinct in Sweden when a few animals established in the 1970s. Over the past 35 years, the species has made a substantial comeback. In this paper, we analyse wild boar population growth using three indices of population size. We also map the legislative decisions and research prompted by the expanding population. We discuss to what extent, in the eyes of the state, the view of wild boar and the management focus has shifted over time, from a perceived pest (eradication) to scarce (conservation), overabundant (reduction/control) or somewhere in between (sustainable management). Results Wild boar harvest started in the early 1990s with a few hundred animals annually and peaked at 161,000 in 2020/2021. The distribution now comprises most of southern Sweden. Analyses of harvest and traffic accidents involving wild boar showed that the population grew exponentially until 2010/2011, after which the increase levelled off. Thus, logistic growth models showed the best fit for the full study period. We recorded 38 legislative decisions or commissions to government agencies regarding wild boar. The first decision in 1981 was to eradicate the free-ranging population. In 1987 however, the parliament decided that wild boar is native to Sweden and should be allowed in restricted extent. Later decisions mainly concerned hunting regulations and hunting methods as direct means to increase harvest and regulate the population. Another topic, increasing in importance over time, was to facilitate the use of wild boar meat to indirectly stimulate harvest. A local outbreak of African swine fever in 2023 necessitated a stamping out strategy in the affected area. We found 44 scientific papers regarding the present free-ranging population. Topics include movements and feeding patterns, hunting, reproduction, and population development. Conclusions The state historically regarded wild boar as a pest to be eradicated. This changed with the decision that wild boar should be allowed in restricted extent, suggesting a conservation approach. In response to population growth, the focus shifted to means facilitating sustainable management and, lately, reducing growth. The story of wild boar in Sweden illustrates attempts to mitigate conflicts and balance interests in wildlife management

From virtually extinct to superabundant in 35 years: establishment, population growth and shifts in management focus of the Swedish wild boar (Sus scrofa) population

Background The wild boar (Sus scrofa) was extinct in Sweden when a few animals established in the 1970s. Over the past 35 years, the species has made a substantial comeback. In this paper, we analyse wild boar population growth using three indices of population size. We also map the legislative decisions and research prompted by the expanding population. We discuss to what extent, in the eyes of the state, the view of wild boar and the management focus has shifted over time, from a perceived pest (eradication) to scarce (conservation), overabundant (reduction/control) or somewhere in between (sustainable management). Results Wild boar harvest started in the early 1990s with a few hundred animals annually and peaked at 161,000 in 2020/2021. The distribution now comprises most of southern Sweden. Analyses of harvest and traffic accidents involving wild boar showed that the population grew exponentially until 2010/2011, after which the increase levelled off. Thus, logistic growth models showed the best fit for the full study period. We recorded 38 legislative decisions or commissions to government agencies regarding wild boar. The first decision in 1981 was to eradicate the free-ranging population. In 1987 however, the parliament decided that wild boar is native to Sweden and should be allowed in restricted extent. Later decisions mainly concerned hunting regulations and hunting methods as direct means to increase harvest and regulate the population. Another topic, increasing in importance over time, was to facilitate the use of wild boar meat to indirectly stimulate harvest. A local outbreak of African swine fever in 2023 necessitated a stamping out strategy in the affected area. We found 44 scientific papers regarding the present free-ranging population. Topics include movements and feeding patterns, hunting, reproduction, and population development. Conclusions The state historically regarded wild boar as a pest to be eradicated. This changed with the decision that wild boar should be allowed in restricted extent, suggesting a conservation approach. In response to population growth, the focus shifted to means facilitating sustainable management and, lately, reducing growth. The story of wild boar in Sweden illustrates attempts to mitigate conflicts and balance interests in wildlife management. Act, Commission, Exponential, Legislation, Logistic, OrdinancepublishedVersio

Fälttestav viltskyddsmedlen PW-viltskydd och Mota

Viltbetning av plantskog utgör idag ett av de svåraste problemen vid föryngring av skog i södra Sverige. Problemet är relativt nytt och har funnits i skogsbruket i större omfattning sedan slutet av 1980-talet. Rådjuren anses vara huvudansvariga för skadorna. För närvarande anses skyddsmedel som appliceras på plantorna vara den metod som är mest kostnadseffektiv. Ett flertal sådana preparat har sedan slutet av 1980-talet introducerats på den svenska marknaden. Tidigare har fälttester av sådana genomförts på Asa försökspark. Denna rapport redovisar två försök som är utförda Med PW-viltskydd och Mota under säsongerna 1995-96 och 1996-97. Den aktiva substansen i både PW-viltskydd och Mota består av starkt doftande eteriska oljor. Medlen sprutas på den övre delen av plantorna med lämplig sprututrustning, eller stryks på med pensel. I ett jämförande repellentförsökjämfördes betningsfrekvens och eventuella skador på plantor vid användning av viltskyddsmedlen PW-viltskydd och Mota i jämförelse med obehandlade kontrollplantor under två säsonger med en ombehandling år 2. I ett dosförsökjämfördes effekten av olika doser av viltskyddsmedlet Mota på betningsfrekvens och eventuella skador på plantorna vid användning av olika doser av medlet under två säsonger med en ombehandling år 2. Doserna i försöket var 1,5 ml/planta, 3 ml/planta, ( normaldos) och 6 ml/planta. Både PW-viltskydd och Mota visade en god viltavskräckande förmåga. Inga skillnader i viltavskräckningseffekt mellan de båda medlen kunde observeras. Betningsskadoma reducerades något vid ökande dos av Mota. Skillnaden var liten i förhållande till den ökade preparatåtgången. Båda preparaten gav upphov till skador på plantornas barr och knoppar. Denna typ av skador kunde konstateras både på nyplanterade plantor och på plantor som växt på hygget under ett år. Plantavgången till följd av både betningsskador och preparatskador var obetydlig. Troligen förvärrades skadorna på plantornas barr och knoppar av klimatisk stress under vårvintern. Barr och knoppskadorna ökade tydligt med ökad dosering av Mota. Vi rekommenderar att tillverkarna av Mota och PW-viltskydd ser över sina doseringsanvisningar och att de även undersöker vilka ingredienser som orsakar plantskadorna och utreder om dessa kan uteslutas ur produkten

The Chevreton Tensor and Einstein-Maxwell Spacetimes Conformal to Einstein Spaces

In this paper we characterize the source-free Einstein-Maxwell spacetimes which have a trace-free Chevreton tensor. We show that this is equivalent to the Chevreton tensor being of pure-radiation type and that it restricts the spacetimes to Petrov types \textbf{N} or \textbf{O}. We prove that the trace of the Chevreton tensor is related to the Bach tensor and use this to find all Einstein-Maxwell spacetimes with a zero cosmological constant that have a vanishing Bach tensor. Among these spacetimes we then look for those which are conformal to Einstein spaces. We find that the electromagnetic field and the Weyl tensor must be aligned, and in the case that the electromagnetic field is null, the spacetime must be conformally Ricci-flat and all such solutions are known. In the non-null case, since the general solution is not known on closed form, we settle with giving the integrability conditions in the general case, but we do give new explicit examples of Einstein-Maxwell spacetimes that are conformal to Einstein spaces, and we also find examples where the vanishing of the Bach tensor does not imply that the spacetime is conformal to a $C$-space. The non-aligned Einstein-Maxwell spacetimes with vanishing Bach tensor are conformally $C$-spaces, but none of them are conformal to Einstein spaces.Comment: 22 pages. Corrected equation (12

Appearance of remodelled and dendritic cell-rich alveolar-lymphoid interfaces provides a structural basis for increased alveolar antigen uptake in chronic obstructive pulmonary disease.

RATIONALE: The alveolar pathology in chronic obstructive pulmonary disease (COPD) involves antigen-driven immune events. However, the induction sites of alveolar adaptive immune responses have remained poorly investigated. OBJECTIVES: To explore the hypothesis that interfaces between the alveolar lumen and lymphoid aggregates (LAs) provide a structural basis for increased alveolar antigen uptake in COPD lungs. METHODS: Lung samples from patients with mild (Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I), moderate-severe (GOLD II-III), and very severe (GOLD IV) COPD were subjected to detailed histological assessments of adaptive immune system components. Never smokers and smokers without COPD served as controls. RESULTS: Quantitative histology, involving computerised three-dimensional reconstructions, confirmed a rich occurrence of alveolar-restricted LAs and revealed, for the first time, that the vast majority of vascular or bronchiolar associated LAs had alveolar interfaces but also an intricate network of lymphatic vessels. Uniquely to COPD lungs, the interface epithelium had transformed into a columnar phenotype. Accumulation of langerin (CD207)(+) dendritic cells occurred in the interface epithelium in patients with COPD but not controls. The antigen-capturing capacity of langerin(+) dendritic cells was confirmed by increased alveolar protrusions and physical T cell contact. Several of these immune remodelling parameters correlated with lung function parameters. CONCLUSIONS: Severe stages of COPD are associated with an emergence of remodelled and dendritic cell-rich alveolar-lymphoid interfaces. This novel type of immune remodelling, which predicts an increased capacity to respond to alveolar antigens, is suggested to contribute to aggravated inflammation in COPD

Null cone preserving maps, causal tensors and algebraic Rainich theory

A rank-n tensor on a Lorentzian manifold V whose contraction with n arbitrary causal future directed vectors is non-negative is said to have the dominant property. These tensors, up to sign, are called causal tensors, and we determine their general properties in dimension N. We prove that rank-2 tensors which map the null cone on itself are causal. It is known that, to any tensor A on V there is a corresponding ``superenergy'' (s-e) tensor T{A} which always has the dominant property. We prove that, conversely, any symmetric rank-2 tensor with the dominant property can be written in a canonical way as a sum of N s-e tensors of simple forms. We show that the square of any rank-2 s-e tensor is proportional to the metric if N<5, and that this holds for the s-e tensor of any simple form for arbitrary N. Conversely, we prove that any symmetric rank-2 tensor T whose square is proportional to the metric must be, up to sign, the s-e of a simple p-form, and that the trace of T determines the rank p of the form. This generalises, both with respect to N and the rank p, the classical algebraic Rainich conditions, which are necessary and sufficient conditions for a metric to originate in some physical field, and has a geometric interpretation: the set of s-e tensors of simple forms is precisely the set of tensors which preserve the null cone and its time orientation. It also means that all involutory Lorentz transformations (LT) can be represented as s-e tensors of simple forms, and that any rank-2 s-e tensor is the sum of at most N conformally involutory LT. Non-symmetric null cone preserving maps are shown to have a causal symmetric part and are classified according to the null eigenvectors of the skew-symmetric part. We thus obtain a complete classification of all conformal LT and singular null cone preserving maps on V.Comment: 36 pages, no figures, LaTeX fil

Exact probabilities for typical ranks of 2 × 2 × 2 and 3 × 3 × 2 tensors

We show that the probability to be of rank 2 for a 2×2×2 tensor with elements from a standard normal distribution is π/4, and that the probability to be of rank 3 for a 3×3×2 tensor is 1/2. In the proof results on the expected number of real generalized eigenvalues of random matrices are applied. For n×n×2 tensors with n≥4 we also present some new aspects of their rank

Wood density traits in Norway spruce understorey: effects of growth rate and birch shelterwood density

Effects of growth rate and birch shelterwood density (0, 300 and 600 trees ha-1) on wood density traits in Norway spruce (Picea abies (L.) Karst.) understorey were evaluated for a trial in the boreal coniferous forest 56 years after establishment of the stand and 19 years after establishment of the trial. Wood density traits were measured by micro-densitometry for annual rings 21-30 extracted at breast height. In addition, ring width and mean density were measured for all annual rings. Growth rate was generally low with a mean ring width of 1.3 mm. Radial variations in ring width and density depended more on calendar year than on cambial age. The shelterwoods had moderate d fluctuations in ring width, but not in wood density. For annual rings 21-30, the mean density was 12 % higher in trees of the lowest growth rate compared to trees of the highest growth rate. Also, minimum density and latewood percentage were higher in trees with the lowest growth rate compared to all other trees, while there were no significant effects due to shelterwood treatment for any of the wood density traits tested. An increase in ring width from 1 to 2 mm resulted in an 18 % decrease in wood density. Latewood percentage explained 84 % of the variation in wood density. (© Inra /Elsevier, Paris.)Caractéristiques de la densité du peuplement dans le sous-étage de sapin de Norvège : effets du taux de croissance et de la densité du peuplement de bouleaux résultant de la régénération par coupes progressives. Les effets du taux de croissance et de la densité du peuplement de bouleau résultant de la régénération par coupe progressive (0, 300 et 600 arbres ha-1) sur les caractéristiques de la densité du peuplement de sapin de Norvège (Picea abies (L.) Karst.) sont évalués pour un essai dans la forêt de conifères boréale 56 ans après l'établissement du peuplement forestier et 19 ans après la mise en place de l'essai. Les caractéristiques de la densité forestière sont mesurées par microdensitométrie pour les anneaux annuels 21-30 extraits à hauteur de poitrine. En outre, la largeur et la densité moyenne des anneaux sont mesurées pour tous les anneaux annuels. On note un taux de croissance généralement faible, avec une largeur moyenne des anneaux de 1,3 mm. Il apparaît que les variations radiales de la largeur et de la densité des anneaux dépendent plus de l'année que de l'âge cambial. Les peuplements résultant de la régénération par coupes progressives présentent des fluctuations modérées dans la largeur des anneaux mais pas dans la densité. Pour les anneaux annuels 21-30, la densité moyenne est supérieure de 12 % pour les arbres ayant le taux de croissance le plus faible par rapport aux arbres dont le taux de croissance est le plus élevé. D'autre part, la densité minimale et le pourcentage de bois d'automne sont plus élevés pour les arbres dont le taux de croissance est le plus faible par rapport à tous les autres arbres, tandis que l'on ne constate aucun effet significatif résultant du mode de régénération par coupes progressives pour aucune des caractéristiques de la densité du peuplement étudiées. On note qu'une augmentation de la largeur des anneaux de 1 à 2 mm se traduit par une baisse de 18 % de la densité du peuplement. Le pourcentage de bois d'automne explique 84 % de la variation dans la densité du peuplement. (© Inra /Elsevier, Paris.