Biogeomorphology in the Anthropocene: a hierarchical, traits-based approach

The complex web of interactions between ecological communities and the physical landscape (biogeomorphology) is being affected by the global scale environmental changes of the Anthropocene. Climate change, habitat destruction, invasions and extinctions are having profound impacts on biogeomorphological process regimes through changes in the composition and activity of ecological communities. However, on the other hand, deliberately-targeted human interventions to biogeomorphic systems have the potential to help mitigate against, and adapt to, the Anthropocene, by managing biogeomorphic processes to enhance resilience. To evaluate these relationships, we propose a conceptual framework based on the ecological concept of functional traits. We review how the Anthropocene is causing changes in species composition, abundance and the prevalence of functional traits to produce changes to biogeomorphic processes and functions that are, as yet, only partly understood. We use examples of fluvial, dryland and coastal biogeomorphic systems to illustrate how purposeful manipulation of biogeomorphic systems (as a type of Nature-based solution) can conserve, enhance or add biogeomorphic functions that are capable of enhancing geomorphic resilience. By focussing on function, this approach offers a range of advantages/avenues for biogeomorphological research. This includes the detection and prediction of human impacts, and an improved understanding of how biogeomorphology can contribute to tackling environmental challenges in the Anthropocene

A controlled field experiment to investigate the deterioration of earthen heritage by wind and rain

Earthen heritage constitutes 10% of sites on the World Heritage List and many of these sites are experiencing extensive deterioration caused by environmental forces, such as wind and rain. This study used a well-established test wall to investigate the impact of environmental conditions on the deterioration of earthen heritage at the remote and under-studied site of Suoyang Ancient City, Gansu Province, China, which is exhibiting widespread deterioration. Test walls have previously been used in earthen heritage research as they allow controlled experiments to be undertaken on complex, realistic structures without risking damage or loss of value to the historic material. This study used portable wind and rain erosion simulation devices to investigate experimentally (i) the comparative effect of wind, sediment-laden wind and wind-driven rain in causing deterioration to earthen heritage and (ii) how the incipient deterioration features produced by wind, sediment-laden wind and wind-driven rain on the test wall relate to the deterioration features recorded on the historic city walls. The test wall was subjected to low, medium and high intensities of clean wind, sediment-laden wind and wind-driven rain. The extent of deterioration produced was measured using repeat, high resolution laser scans before and after each test run. The deterioration features caused by each environmental force were notably different with clean wind removing the loose surface material, sediment-laden wind causing pitting and wind-driven rain causing incipient gullying. These incipient features compare well with more developed features seen on the historic walls. Wind-driven rain caused the greatest amount of deterioration while clean wind caused the least. However, as the frequency and duration of wind events at Suoyang is much greater than those of rain events, wind is likely to play an important role in the deterioration of earthen heritage over annual timescales. These findings show that conservation strategies at rammed earth sites like Suoyang need to address the impact of multiple environmental forces, such as clean wind, sediment laden wind and wind-driven rain

Comparability of non-destructive moisture measurement techniques on masonry during simulated wetting

Detecting the presence of moisture in historical masonry is essential to understanding how a structure interacts with the environment, and diagnosing the potential for damage from a range of physical, chemical, and biological processes. In-situ, non-invasive diagnostic techniques have been developed in preference to methods that require irreversible modifications to a structure. These techniques include: electrical resistivity, microwaves, and infrared thermography. Independently, these approaches provide limited snapshots of surficial and internal moisture regimes; this project sought to assess the comparability of multiple techniques. Simulated post-rain spell drying was monitored over 48 h on limestone and sandstone monoliths in a controlled laboratory environment and also in ambient conditions on purpose-built masonry located in Oxfordshire, UK. Repeat measurements were taken using electrical resistance tomography (ERT), electrical and microwave moisture meters, and infrared thermography. Three aspects of comparability are discussed: i) data transformations and geological comparability, ii) depth-resolving meter readings, iii) the localised benefits of employing multiple technologies and instruments

Assessing the Long-term Success of Reigate Stone Conservation at Hampton Court Palace and the Tower of London

Reigate stone was extensively used in medieval London and is prone to rapid decay. A variety of different conservation treatments has been applied in the past; in many cases, these have not mitigated on-going decay. This paper presents an overview of wax, limewash, silane and ammonium tartrate treatment at the Tower of London and Hampton Court Palace. Documentary analysis and visual inspection indicate that whilst these methods have provided protection to some stones, no single method has resulted in the protection of all stones. Non-destructive and minimally-destructive testing is used to more closely assess the effects of ammonium tartrate treatment. The results imply that inherent stone mineralogy, past decay pathways and/or present environmental factors are a greater influence on on-going decay than treatment histories

Characterisation of building exposure to wind-driven rain in the UK and evaluation of current standards

One method of estimating WDR exposure is semi-empirical formulae based on hourly meteorological data including ISO 15927–3:2009 and BS 8104:1992. These provide protocols to estimate extreme WDR exposure, such as the worst spell likely to occur in any given three-year period. This study characterises the amount of annual WDR exposure and the frequency and duration of directional WDR spells for eight sites in the UK from 1986 to 2015. To assess the utility of these standards for evaluating extreme WDR exposure at those sites, the worst spell likely to occur in any given three-year period is determined using a ‘return period’ approach from extreme value analysis (EVA). It is shown that in the context of the prevailing wind patterns in the UK wall orientation is an important factor in determining the frequency and duration of WDR spell properties. EVA is applied for eight sites in the UK from 1959 to 1991 to evaluate the methods and climatic data used in BS 8104:1992 and their relevance to current climate. Both standards underestimate the volumetric exposure of the ‘once every three years’ spell compared to EVA for methodological reasons but are useful tools to assess annual exposure and compare between sites