Introduction and background: interpretations of landscape change (1999)

Research into the origins of landscape has a long and distinguished tradition. In America, landscape studies form the core of physical geology while elsewhere the study of landscape development has spread beyond the confines of geology to develop a firmer foothold in the geographical tradition, particularly in geomorphology. The development of ideas in landscape study has, however, been neither steady nor sequential. It has been characterized instead by several major conceptual shifts interspersed with periods of reinforcement or neglect. Within geomorphology, and certainly within the English-speaking world, the most important of these shifts occurred in the early 1960s with the move from denudation chronology of landscapes as a core activity to an emphasis on process-based investigation of individual landforms. In geology, the 1960s also marked an important change in perspective. Publication of plate tectonic theories (sea-floor spreading, continental drift, subduction and mountain building) had far-reaching consequences for all earth science. In particular, plate tectonics made the study of apparently ancient processes (billions of years old) applicable to the present-day with, for example, application to earthquake studies. Whilst the initial shift towards process studies was a response to the desire for a better understanding of the mechanisms driving landscape change, it was not long before this goal became relegated in the eyes of many of its practitioners. As a consequence, process study became an end in itself, rather than a means to an end. This movement has been reinforced in recent years by a demand for greater 'relevance' from, for example, research funding bodies resulting in an emphasis on problem solving and wealth generation that has moved away from studies at the landscape scale. Consequently, within geomorphology, process studies and applied geomorphology have come to dominate the literature a dominance reinforced by the increasing division and separation of the discipline into process domains such as fluvial and glacial studies. This has reached the point where many researchers would now naturally identify themselves as specialists in a particular process rather than as geomorphologists. A similar trend can be identified within geology, whereby studies of uplift, erosion and stability clearly fall into pre-plate tectonics and post-plate tectonics generations. In the 1920s, studies of denudation were popular, as evidenced by the volume of work conducted in southern England and based largely on observations of palaeovaUeys, tilted strata and unconformities. Sediment provenance became important in the 1920s and 1930s and early works on the use of heavy minerals in studies of past erosion were developed. By the 1960s geologists were standing back and viewing many processes in terms of their global plate tectonic significance. However, this emphasis on processes inevitably led to the development of more labour-intensive analytical methods, as a consequence of which, the wider perspective began to be neglected. Through the 1970s and 1980s, therefore, studies of uplift developed using methods that determine heating or pressurization of the uplifted rocks. Thermal estimates of uplift, including spore or conodont alteration indexes, fluid inclusion studies and diagenetic models were developed, together with estimates of pressurization including studies of mineralogy and sonic borehole logs. However, perhaps the most significant advance in the determination of uplift rates and amounts has been in the field of apatite fission track analysis (AFTA) (Carter 1999). The widespread use of AFTA in the oil industry has provided large datasets that encompass the offshore basins formerly ignored by those concerned with land erosion (Buchanan & Buchanan 1995). Studies of erosion and palaeoerosion have also developed from the study of derived clasts to clay minerals and heavy minerals, requiring increasingly labourintensive, and hence specialist, methods to derive local or even regional perspectives. Specialization clearly has many advantages. If, however, it is allowed to proceed unchecked, these advantages eventually come to be outweighed by the effects of an increasingly reductionist approach whereby concentration on small-scale studies and the pursuit of ever greater detail detracts from appreciation of the largescale picture and ultimately fragmentation and loss of the subject core. Clearly, the longer this reductionist/segregationist approach persists the more difficult it is to define and to justify the existence of the original parent discipline.