Showing papers on "Marginal land published in 1975"

Secular climatic change and marginal agriculture

Abstract: An assessment is made of the significance of secular climatic change to marginal cultivation in south-east Scotland Climatic limits to cultivation in this region occur at levels of about 1050 day-degrees C, 60 mm PWS and 6-2 m/s average windspeed. These limits stood at 320-350 m in the late nineteenth century, yet 700 ha of abandoned medieval cultivation lie above them. Secular changes in temperature and rainfall are resolved into trends in accumulated temperature and PWS. These reveal a substantial deterioration in upland growing conditions after 1250. The climatic limit to cultivation may have fallen 140 m over 300 years. Isopleths of this limit, drawn for selected periods, point to an upland fringe which may have become submarginal to cultivation. A spatial correlation between this submarginal fringe and the distribution of abandoned farmland may suggest an indirect causal relationship. IT HAS recently been recognized that fluctuations of climate have a special significance for mar- ginal areas, where agriculture is often poorly adapted to climatic conditions.1 The implication is that future decisions on the use of marginal land will require information on the variability of climate and the likelihood of sequences of poor years.2 But the implications of climatic change for the former use of marginal land have not been satisfactorily assessed. Although Manley, Lamb and Ladurie have shown that substantial long-term fluctuations of climate have occurred over the last millenium,3 it is evident that some historians and geographers have not seriously considered these to have been important agents of agricultural change.4 Where attention has been given to climatic change, it has generally been drawn toward short-term fluctuations that are more readily measured and were more frequently recognized by contemporary observers.5 This paper seeks to assess the significance of long-term climatic change in upland Britain. It aims to test the hypothesis that a secular deterioration of climate caused much of the high- lying cultivation in Scotland to become profoundly sub-marginal in the seventeenth century; that, while the immediate stimuli to abandonment of this cultivation may have been short-term harvest failure, soil exhaustion, a fall in population or the decay of the monastic farming system, the response to these stimuli would neither have been so widespread nor so permanent had the potential for upland cropping not been so severely reduced over the preceding two or three centuries. Particular reference is made to those changes of climate which may have occurred in the Lammermuir Hills in south-east Scotland, and to their possible correlation with the advance and retreat of early cultivation in this region. The choice of this study area was dictated by its low relief and gentle slopes, which ensured that any response by the cultivation limit to alti- tudinal or temporal changes in climate was manifested over a wide range of marginal foothill. The significance of climatic change in this region may be discussed as a sequence of four operations. First, parameters are established for selected climatic restraints on subsistence cereal cultivation in upland Scotland. Secondly, the nature in which these restraints operate is discussed as a probability of harvest failure. Secular changes in rainfall and temperature are then resolved into movements of isopleths of these restraints. Finally, movements of the isopleths are compared with the advance and retreat of cultivation to test for a causal relationship.