Large-Scale Impacts of Land-Use Change in a Scottish Farming Catchment
A catchment is an area of land defined by the origins and discharges of all tributary streams feeding large rivers flowing into the sea. It is therefore a natural bio-physical unit distinct from adjacent catchments and forms the obvious basis for integrat
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Large-Scale Impacts of Land-Use Change in a Scottish Farming Catchment A.F. Zuur, D. Raffaelli, A.A. Saveliev, N.J. Walker, E.N. Ieno, and G.M. Smith
15.1 Introduction A catchment is an area of land defined by the origins and discharges of all tributary streams feeding large rivers flowing into the sea. It is therefore a natural bio-physical unit distinct from adjacent catchments and forms the obvious basis for integrated environmental management policies. In Europe, river catchments tend to be dominated by agriculture, at least at lower altitudes. In the case of the Ythan catchment (Fig. 15.1), Aberdeenshire, Scotland, where the river rises at only a few hundred metres, more than 90% of the land area is now under agricultural production. Much of this is arable crops like wheat, barley, and oil-seed rape, which demand high inputs of chemical nitrogen. The Ythan catchment also hosts large numbers of pigs and other livestock (and also some of the authors of this book). Whilst the Ythan catchment has always been prime agricultural land, there have been major changes in land-use over the past 40 years because of market trends and drivers such as the Common Agriculture Policy. This policy encouraged growing of crops through subsidies not previously available for crops such as barley and wheat at the expense of less profitable crops such as oats. The conversion of grassland to cereals, increased application of nitrogen, and increase in animal manures and slurries over the past 40 years have inevitably affected water quality, specifically elevated levels of nitrate. These levels were so high in the 1990s that the Ythan catchment had the distinction of being the first in the UK to be designated a Nitrogen Vulnerable Zone under the European Community Nitrates Directive. Staff at Culterty Field Station, University of Aberdeen, were able to document and describe trends in this process in great detail through a series of monitoring programmes, data analyses, and field experiments. Data on land-use were obtained from ‘parish returns’ – records of amounts of land under different crops and numbers of animals held for each farm in the parish that are returned to the Scottish Records Office annually. These data were extracted for all parishes (community A.F. Zuur (B) Highland Statistics Ltd., Newburgh, AB41 6FN, United Kingdom
A.F. Zuur et al., Mixed Effects Models and Extensions in Ecology with R, Statistics for Biology and Health, DOI 10.1007/978-0-387-87458-6 15, C Springer Science+Business Media, LLC 2009
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Fig. 15.1 Small part of the Ythan estuary. The photograph was taken by Alain Zuur
administrative areas) within the catchment for land under oats, wheat, oil-seed rape, barley, and for numbers of pigs, cattle and sheep for the period 1960s to 1990s. Levels of nitrates (only small amounts can be attributed to sewage) were extracted from databases held by the North-East River Purification Board and supplemented by the field station’s own observations. The environmental impact of high levels of n
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