Cape cormorants decrease,move east and adapt foraging strategies following eastward displacement of their main prey

Numbers of Cape cormorants Phalacrocorax capensis breeding in South Africa decreased by nearly 50% from approximately 107 000 pairs in 1977–1981 to 57 000 pairs in 2010–2014. Although four colonies had >10 000 pairs in 1977–1981, there was just one such colony in 2010–2014. Almost all the decrease occurred after the early 1990s off north-west South Africa, between the Orange River estuary and Dassen Island. South of this, the number breeding in the two periods was stable, with some colonies being formed or growing rapidly in the 2000s. The proportion of South Africa’s Cape cormorants that bred south of Dassen Island increased from 35% in 1977–1981 to 66% in 2010–2014, with the opposite situation observed in the north-west. This matched a shift to the south and east in the distributions of two of the Cape cormorant’s main prey species, anchovy Engraulis encrasicolus and sardine Sardinops sagax. In 2014, an apparent scarcity of prey in the north-west resulted in Cape cormorants attempting to take bait from hooks of fishing lines over an extended period, a behaviour not previously recorded. The number of Cape cormorants breeding in the south may be constrained by the absence of large islands between Dyer Island in the west and Algoa Bay in the east. If so, it may be possible to bolster the southern population through the provision of appropriate breeding habitat, such as platforms, or restricting human disturbance at suitable mainland cliff breeding sites.     

Carrying capacity of the eastern ecological gradient of Kenya

Kenya's rate of natural population increase exceeds 4.0%/year. At this rate, Kenya's population of 23.5 million will expand to 35 million by the year 2000. Rural migrants are being forced out of the highlands into marginal arid and semiarid regions to the east and south in the eastern ecological gradient including Meru, Kitui, Machakos, and Kajiado districts. The people have become victims of marginalization by which the productivity of a unit of land declines relative to the demands of its occupants. The concept of carrying capacity means the number of people a given area can sustain over the long term. In Maasailand, 3.5 standard stock units (450 kg each) are required per adult equivalent for full subsistence, about 7 cows/person. For the Maasai pastoralists, carrying capacities were examined at 2 levels of subsistence: 100% from the herds and 80% from the herds; 2 technological levels; and population-growth rates of 2%, 2.5%, and 3%/annum. Using the median, 3.5%/year, population-growth scenario these districts will have almost 5 million inhabitants in the year 2000. Poverty at technology level I for 40% of them, or for 2 million people, is implausible. Technology level II implies that current rural-development programs will succeed with technological innovations for farm households, access to credit, and markets for their produce. Level II is likely to prevail toward the end of the century for the majority of farmers. Level III necessitates best agricultural and livestock technology as well as the best management. At most, 25% of the households of the eastern ecological gradient could enter this realm by the year 2000. Current strategies of voluntary family planning, rural development emerging from an antiquated extension system, inability to address inequity in land distribution, and laissez-faire resource management are inadequate to deal with the pace of change.     

The frequency of hail occurrence

Summary Hail occurrence, being a comparatively rare event, is fit well by the Poisson distribution providing the hail storms are independent. When this condition is not met, hail occurrence follows the negative binomial distribution. A test is given which determines whether the Poisson distribution may be used, or whether the negative binomial is necessary. The parameter of the Poisson distribution is always estimated efficiently by the method of moments. The parameters of the negative binomial distribution, however, are only efficiently estimated by the method of moments under certain conditions; when the method of moments fails, the method of maximum likelihood must be employed. A criterion to determine when this method must be used is given together with the method of obtaining the estimates. The methods presented are illustrated by application to several hail records.

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Zusammenfassung Unter der Voraussetzung, daß die Hagelfälle voneinander unabhängig sind, kann das Auftreten dieses verhältnismäßig seltenen Ereignisses gut durch eine Poissonsche Verteilung dargestellt werden; ist dies nicht der Fall, dann folgt es einer negativ binomischen Verteilung. Es wird eine Testmethode mitgeteilt, nach welcher man entscheiden kann, ob die Poissonsche oder die negativ binomische Verteilung zu verwenden ist. Die Parameter der Poissonschen Verteilung können mit der Methode der Momente immer zuverlässig bestimmt werden. Die Parameter der negativ binomischen Verteilung jedoch können mit dieser Methode nur unter bestimmten Umständen ermittelt werden. Falls die Methode der Momente versagt, ist die Methode der größten Wahrscheinlichkeit anzuwenden. Ein Kriterium zur Entscheidung, wann diese Methode angewendet werden muß, sowie eine Methode zur Ermittlung genäherter Werte werden mitgeteilt. Die beschriebenen statistischen Methoden werden durch Anwendung auf einige Hagelbeobachtungsreihen erläutert.

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Résumé En admettant que les chutes de grêle sont indépendantes les unes des autres, on peut convenablement représenter leur apparition par une distribution de fréquences de Poisson. Si cen'est pas le cas, ces chutes obéissent à une distribution binomiale négative. L'auteur propose un test permettant de décider s'il convient d'appliquer la première ou la seconde distribution. On peut toujours déterminer les paramètres de la distribution de Poisson par la méthode des moments; pour la distribution binomiale négative ce n'est possible que sous certaines conditions. Si la méthode des moments échoue, on aura recours à celle de la plus grande probabilité. L'auteur discute un critère pour l'emploi de cette dernière ainsi qu'une méthode pour obtenir des valeurs approchées. Les méthodes statistiques décrites sont illustrées par des applications à quelques séries d'observations de la grèle.

     

Climatological analysis of snowfall thresholds

The climatological analysis for the first occurrence of 24-hour snowfalls of various depths is developed. This gives the probability function of snowfall thresholds which in turn makes any quantiles or probability values readily available. The probability function together with a special convention on years with no threshold value leads also to a definition of mean or expected threshold date. Examples of applications to several thresholds for New England data are presented.

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Zusammenfassung Es wird eine klimatologische Analyse für das erste Auftreten von 24stündigen Schneefällen verschiedener Schneehöhe entwickelt. Dies führt zu der Wahrscheinlichkeitsfunktion von Schneefall-Schwellenwerten, woraus sich beliebige Teilquantile oder Wahrscheinlichkeitswerte gewinnen lassen. Die Wahrscheinlichkeitsfunktion zusammen mit einer Annahme über die Jahre ohne Erreichen des Schwellenwerts führt auch zu einer Definition des mittleren oder zu erwartenden Schwellenwertdatums. Schließlich werden Anwendungsbeispiele für bestimmte Schwellenwerte an Hand von Daten aus Neu-England gegeben.

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Résumé L'auteur développe une analyse climatologique de la première apparition de chutes de neige dans l'intervalle de 24 heures d'épaisseur différente. Celle-ci conduit à la fonction de probabilité des valeurs limites des chutes de neige à partir de laquelle on peut calculer à volonté de quantiles et de valeurs de probabilité. En admettant une convention spéciale concernant les années qui n'atteignent pas de valeurs limites, la fonction de probabilité perment aussi de déterminer la date limite moyenne ou probable. Pour terminer, l'auteur donne quelques exemples d'application pour certaines valeurs limites à partir de données de la Nouvelle Angleterre.

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With 3 Figures

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Presented at the meeting of the Northeast Snow Conference Burlington, Vermont, February 10, 1955.     

Geography,planning and the law: a coastal perspective

This paper examines how legal structures interact with land‐use decisions in the coastal zone. The emphasis is on NSW where there has been a steady evolution of legislative and other measures to regulate how the coast is to be planned and managed. These measures arise from a long history of individual, corporate, local government and State agency actions directed more at private benefit than at protecting and conserving environmental values for the public good. Alienation of foreshores, restrictions on access, buildings located in hazardous areas, canals exposing soils rich in acids, and pollution of waterways are examples of degradation on this coast. Yet much remains to be protected. Expansion of coastal national parks over the past decade has helped. But new planning controls have been introduced to support the NSW Coastal Policy (1997 NSW Coastal Policy (1997) A sustainable future for the New South Wales coast NSW Government, Sydney  [Google Scholar]). In essence, there is evidence that the State government seeks to implement environmentally sustainable development principles to ensure that as the population continues to grow, decisions on future land uses will reflect the functioning of ecosystems and the dynamics of coastal and catchment geomorphology and hydrology. Pressures from individuals and corporations exercising traditional property rights need to be managed within a statutory framework that facilitates sustainability of coastal environmental values cherished by so many.     

Making Space for Failure in Geographic Research

The idea that field research is an inherently “messy” process has become widely accepted by geographers in recent years. There has thus far been little acknowledgment, however, of the role that failure plays in doing human geography. In this article we push back against this, arguing that failure should be recognized as a central component of what it means to do qualitative geographical field research. This article seeks to use failure proactively and provocatively as a powerful resource to improve research practice and outcomes, reconsidering and giving voice to it as everyday, productive, and necessary to our continual development as researchers and academics. This article argues that there is much value to be found in failure if it is critically examined and shared, and—crucially—if there is a supportive space in which to exchange our experiences of failing in the field.     

Biologically induced mineralization of dypingite by cyanobacteria from an alkaline wetland near Atlin,British Columbia,Canada

Background  

This study provides experimental evidence for biologically induced precipitation of magnesium carbonates, specifically dypingite (Mg₅(CO₃)₄(OH)₂·5H₂O), by cyanobacteria from an alkaline wetland near Atlin, British Columbia. This wetland is part of a larger hydromagnesite (Mg₅(CO₃)₄(OH)₂·4H₂O) playa. Abiotic and biotic processes for magnesium carbonate precipitation in this environment are compared.     

An Improved Mean-Gravity Model for GPS Hydrostatic Delay Calibration

The determination of global positioning system (GPS) heights with submillimeter accuracy needs proper correction of tropospheric delay. In this letter, the modeling of zenith hydrostatic delay (ZHD) was addressed, considering that wet delay must be treated separately. ZHD is traditionally estimated from Saastamoinen's formula using a mean-gravity model and surface pressure observations. The uncertainty in ZHD associated with the mean-gravity model is about 0.3 mm. An improved parametric model is derived here, which yields an uncertainty in the ZHD less than 0.1 mm when the surface altitude lies in the range of 0-9 km. A second parametric model is derived for higher altitudes (such as above radiosonde observations or atmospheric models). Both parametric models depend on latitude, height, and time variables. This dependence is due to the link between the mean gravity and temperature profiles between the surface and ~80-km altitude. The uncertainty in the parametric models due to short-term temporal variability of the temperature profiles is shown to produce an uncertainty in ZHD smaller than 0.1 mm     

Patterns and trends in seabird bycatch in the pelagic longline fishery off South Africa

Both foreign and domestic pelagic longline fishing vessels operate in South Africa’s Exclusive Economic Zone and adjacent international waters where they kill hundreds of seabirds each year as bycatch. To update assessments of the impact of the pelagic longline fishery on seabirds off South Africa, information on necropsied seabirds and national fisheries observer bycatch records were summarised for 2006–2013. Foreign-flagged (Asian) vessels had 100% observer coverage throughout the study period, whereas only 6% of the fishing effort by South African-flagged vessels was observed (with no coverage in 2011–2013). Vessels with observers caught seabirds at a rate of 0.132 birds per 1 000 hooks, resulting in an estimated mortality of 2 851 individuals (356 per year) comprising 14 species. Extrapolation of the observed fishing sets to the unobserved fishing sets by the South African domestic longline fleet suggested that approximately 750 additional birds were likely killed during the study period, therefore a combined 450 birds were killed per year. White-chinned petrel Procellaria aequinoctialis was the most frequently killed species (66%), followed by ‘shy-type’ albatrosses Thalassarche cauta/steadi (21%), black-browed albatross T. melanophris (7%), Indian yellow-nosed albatross T. carteri (3%), and Cape gannet Morus capensis (2%). The seabird bycatch rates were lower than in 1998–2005. Nationality of the vessel, time of line-setting, moon phase, year, season, fishing area, and seabird bycatch mitigation measures all influenced seabird mortality. Concurrent with 100% observer coverage, significant reductions in the seabird bycatch rate occurred in the Asian fleet in the latter years of the study, and these rates now approximate the national target (0.05 birds per 1 000 hooks). However, seabird bycatch rates remained high in the South African fleet, where no observers were deployed during 2011–2013, highlighting the need for independent observer programmes in fisheries—a matter of global interest. Suggestions are made as to how seabird bycatch by pelagic longline fisheries off South Africa may be further reduced.