Understanding the effects of cattle grazing in English chalk streams

Abstract

Accounting for much of the landscape of southern England, chalk stream environments hold significant cultural, economic and ecological value. However, attempts to retain this value are often hindered by the remnants of historic management practices that have occurred across several millennia, as well as contemporary demands upon chalk stream amenity, including water abstraction, recreational use and fisheries management. One land-use that is believed to have a detrimental effect upon chalk streams, but which has been inadequately researched, is cattle grazing.

Within this thesis the effects of cattle grazing in English chalk streams are assessed using a range of techniques. Terrestrial laser-scanning is employed to show that cattle can cause small, local changes in river bank topography. Direct and remote observations are used to link cattle behaviour to landscape utilisation, and a staticially significant correlation between air temperature and in-stream cattle activity is identified. Laboratory faecal analysis is conducted to establish the nutrient loading due to cattle, with results showing that cattle faeces contain signfiicant concentrations of phosphate. In-stream water turbidity monitoring is combined with remotely sensed cattle behaviour data to demonstrate that in-stream cattle activity has a minimal effect upon suspended sediment concentrations in an English chalk stream. A study using the diffuse fine sediment risk model, SCIMAP, highlights the hydrologically disconnected nature of English chalk streams, with model outputs concluding that topography, rather than land-use (cattle grazing), is the key control on diffuse fine sediment risk in English chalk streams.

Combined, these individual findings provide a detailed, inter-disciplinary assessment that concludes the effects of cattle grazing in English chalk streams are different to those recorded in research from other environments, with physio-chemical effects (i.e. nutrient loading) being of greater significance than geomorphological agency (i.e. river bank destabilisation). This overarching conclusion has implications for the management of cattle grazing in English chalk streams, and these are discussed.

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ORCID for D.A. Sear: orcid.org/0000-0003-0191-6179

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