A commentary on climate change, stone decay dynamics and the ‘greening’ of natural stone buildings: new perspectives on ‘deep wetting’

Environmental controls on stone decay processes are rapidly changing as a result of changing climate. UKCP09 projections for the 2020s (2010–2039) indicate that over much of the UK seasonality of precipitation will increase. Summer dryness and winter wetness are both set to increase, the latter linked to projected precipitation increases in autumn and spring months. If so, this could increase the time that stone structures remain wet and possibly the depth of moisture penetration, and it appears that building stone in Northern Ireland has already responded through an increased incidence of algal ‘greening’.This paper highlights the need for understanding the effects of climate change through a series of studies of largely sandstone structures. Current and projected climatic trends are therefore considered to have aesthetic, physical and chemical implications that are not currently built into our models of sandstone decay, especially with respect to the role played by deep-seated wetness on sandstone deterioration and decay progression and the feedbacks associated with, for example surface algal growth. In particular,it is proposed that algal biofilms will aid moisture retention and further facilitate moisture and dissolved salt penetration to depth. Thus, whilst the outer surface of stone may continue to experience frequent wetting and drying associated with individual precipitation events, the latter is less likely to be complete, and the interiors of building blocks may only experience wetting/drying in response to seasonal cycling. A possible consequence of deeper salt penetration could be a delay in the onset of surface deterioration,but more rapid and effective retreat once it commences as decay mechanisms ‘tap into a reservoir of deep salt’.

Understanding the decay of stone-built heritage

The problem of the decay and conservation of stone-built heritage is a complex one, requiring input across many disciplines to identify appropriate remedial steps and management strategies. Over the past few decades, earth scientists have brought a unique perspective to this challenging area, drawing on traditions and knowledge obtained from research into landscape development and the natural environment. This paper reviews the crucial themes that have arisen particularly, although not exclusively, from the work of physical geographers — themes that have sought to correct common misconceptions held by the public, as well as those directly engaged in construction and conservation, regarding the nature, causes and controls of building stone decay. It also looks to the future, suggesting how the behaviour of building stones (and hence the work of stone decay scientists) might alter in response to the looming challenge of climate change.

Like a rolling stone: the mobility of maerl (Corallinaceae) and the neutrality of the associated assemblages

Beds of nonattached coralline algae (maerl or rhodoliths) are widespread and considered relatively species rich. This habitat is generally found in areas where there is chronic physical disturbance such that maerl thalli are frequently moved. Little is known, however, about how natural disturbance regimes affect the species associated with maerl. This study compared the richness, animal abundance, and algal biomass of maerl-associated species over a two-year period in a wave-disturbed bed and a sheltered maerl bed. Changes in associated species over time were assessed for departures from a neutral model in which the dissimilarity between samples reflects random sampling from a common species pool. Algal biomass and species richness at the wave-exposed site and on stabilized maerl at the sheltered site were reduced at times of higher wind speeds. The changes in species richness were not distinguishable from a neutral model, implying that algal species were added at random to the assemblage as the level of disturbance lessened. Results for animal species were more mixed. Although mobile species were less abundant during windy periods at the exposed site, both neutral and non-neutral patterns were evident in the assemblages. Artificial stabilization of maerl had inconsistent effects on the richness of animals but always resulted in more attached algal species. While the results show that the response of a community to disturbance can be neutral, the domain of neutral changes in communities may be relatively small. Alongside non-neutral responses to natural disturbance, artificial stabilization always resulted in an assemblage that was more distinct than would be expected under random sampling from a common pool. Community responses to stabilization treatments did not consistently follow the predictions of the dynamic equilibrium model, the intermediate disturbance model, or a facilitation model. These inconsistencies may reflect site-specific variation in both the disturbance regime and the adjacent habitats that provide source populations for many of the species found associated with maerl.

Welfare epidemiology as a tool to assess the welfare impact of inherited defects on the pedigree dog population

The effect that breed standards and selective breeding practices have on the welfare of pedigree dogs has recently come under scrutiny from both the general public and scientific community. Recent research has suggested that breeding for particular aesthetic traits, such as tightly curled tails, highly domed skulls and short muzzles predisposes dogs with these traits to certain inherited defects, such as spina bifida, syringomyelia and brachycephalic airway obstruction syndrome, respectively. Further to this, there is a very large number of inherited diseases that are not related to breed standards, which are thought to be prevalent, partly as a consequence of inbreeding and restricted breeding pools. Inherited diseases, whether linked to conformation or not, have varying impact on the individuals affected by them, and affect varying proportions of the pedigree dog population. Some diseases affect few breeds but are highly prevalent in predisposed breeds. Other diseases affect many breeds, but have low prevalence within each breed. In this paper, we discuss the use of risk analysis and severity diagrams as means of mapping the overall problem of inherited disorders in pedigree dogs and, more specifically, the welfare impact of specific diseases in particular breeds.

Measuring health-related quality of life after stroke: A brief tool.

Routine assessment of health-related quality of life (HRQoL) can be time consuming and burdensome for a person with stroke. Therefore the aim of this study was to develop and test a brief instrument for assessing HRQoL among people with stroke. The Quality of Life after Stroke Scale (QLASS) was constructed from items within the Quality of Life Index-Stroke Version and the Chronic Respiratory Disease Questionnaire. It was administered to 92 people with stroke at three points in time: immediately after discharge from hospital, 6 months and 12 months later. Results suggest that the QLASS has 19 items which represent three factors: emotional functioning, mastery and fatigue which correlate with valid measures of health status and activities of daily living. The QLASS is proposed as a brief, valid HRQoL tool for use among people with stroke.

The pressure distribution along stone columns in soft clay under consolidation and foundation loading

The mechanism whereby foundation loading is transmitted through the column has received little attention from researchers. This paper reports on some interesting findings obtained from a laboratory-based model study in respect of this issue. The model tests were carried out on samples of soft clay, 300 mm in diameter and 400 mm high. The samples were reinforced with fully penetrating stone columns, of three different diameters, made of crushed basalt. Four pressure cells were located along each stone column. The 60 mm diameter footing used in the model was supported on a clay bed reinforced with a stone column and subjected to foundation loading under drained conditions. The results show that the dissipation of excess pore water pressure developed during the initial application of total stresses, when the foundation was subjected to no loading, generated considerable stresses within the column, and that this was directly attributable to the development of negative skin friction. The pressure distributions in the column during foundation loading showed some complex behaviour.