Duncan Mcgregor

• University of London

This paper outlines pressures on agricultural land in periurban Kumasi, Ghana. A survey of agricultural practices underlines the recent and rapid transition from agricultural to urban land use in the periurban interface, and shows how farmers are reacting by reducing fallow periods. Farmers are also intensifying agriculture near streams and rivers...

The purpose of this study is to reach a basic understanding of drought and climate change in southwestern Jamaica through an integration of local knowledge and perception of drought and its physical characteristics manifested in remotely sensed precipitation and vegetation data. Local knowledge and perception are investigated through a survey of si...

This paper reports on ongoing research on the impact of global environmental and economic change on small farming in Jamaica using a case study of southern St. Elizabeth. The area is one of the principal small farming regions in the country and supplies both the domestic market and the Jamaican tourist industry. Farmers in this rain shadow region a...

International discourses on environment and development help to shape global shared understandings of environmental issues. This paper describes the environment and development history of Guyana and Jamaica through pre-colonial, colonial, independence and market liberalisation stages. Two opposing discourses are used to frame this history: a domina...

Variability of composition and of pebble shape in river gravels are discussed. Catchment changes, progressive down-valley changes and less systematic cross-valley effects are recognized as sources of variability. Intercomponent ratios and pebble shape are analysed in the Pleistocene gravels of the Thames and its tributaries between High Wycombe and...

The recognition of materials and structures which are unrelated to the original floodplain processes of terrace formation is essential to the proper understanding of terrace morphology and stratigraphy. Two groups of processes have been active in modifying the Lower and Middle Pleistocene terraces of the River Thames since their formation: non-fluv...

Examines the physical conditions of a small area on the southern flank of the Fall River Basin. In much of the area, inappropriate methods of cultivation have led to severe soil erosion, and progressive deterioration of agricultural land is evident throughout the area. -Author

This paper discusses the growing interest among researchers and international agencies in better understanding the rural-urban interface in Africa. It also illustrates the key features of this interface and associated definitional issues, drawing on research in eight villages around the city of Kumasi in Ghana. All villages had processes of change...

Incl. abstract and bibl. references This paper reflects critically on issues of North-South collaboration and participatory research arising from a project on participatory and sustainable local-level environmental management in the peri-urban area surrounding Kumasi, Ghana. Rapid immigration, uncoordinated conversion of farmland to housing, intens...

River-channel and colluvial deposits, near Marsworth, Buckinghamshire, record a temperate-periglacial-temperate sequence during the late Middle Pleistocene. The deposits of a lower channel contain tufa clasts bearing leaf impressions that include Acer sp., and Sorbus aucuparia and containing temperate arboreal pollen attributed to ash-dominated woo...

On the basis of gravel composition, the earliest evidence of a Thames drainage system that extended into East Anglia is in the Norwich Crag. An influx of quartz into the high level pebble gravels of the middle Thames is traced across Essex into the Creeting Sands in the Norwich Crag near Ipswich. Another influx of far-travelled material entered the...

The contemporary geomorphological and agricultural status of the Fall River catchment, Jamaica, is examined. The principal constraints which have hampered development are steeply sloping terrain, application of inappropriate soil conservation measures, and the cessation of direct funding associated with the demise of the former Yallahs Valley Land...

Clearance of evergreen seasonal forest for cattle pasture is examined in an area of northern Roraima. Colonião (Panicum maximum Jacq.) and kikuyu grass (Brachiaria humidicola (Rendle) Schweik.) are commonly established on cleared forest land. Current rates of clearance are rather low as also is grazing intensity (1–2 animals ha−1), but soil physica...

Soil conditions under pasture were examined in a range of sites representing the sequence of conversion of forest to pasture at two locations in the vicinity of Ilha de Maracã, Roraima. Comparisons were made with adjacent savana. Soil bulk densities shown to increase after forest clearance and soil chemical data indicate that the initial beneficial...

The geomorphological materials and forms of the Maraca area of Roraima, Brazil are described, an their sgnificance for land development examined. Significant contrasts are noted in areas presently under rainforest and savanna vegetation. Lateritic gravels and extensive shetwash accumulations in savanna areas constrast with incipient or absent plint...

The Orfordness shingle consists largely of flint. However, depending on particle size, non-flint components usually form 5–10 per cent of the material. Composition of the non-flint fraction indicates derivation from Pleistocene outcrops to the north. Typical of such outcrops are relative scarcity of quartz and the common presence of Rhaxella and Ca...

In the Pleistocene sediments of the north Norfolk coast, four main types of gravel deposit are distinguished in terms of composition and stratigraphic position. The oldest gravels, of Pre-Pastonian age or older, reached the area from the south through the main artery of the proto-Thames system. They include material which entered that system from t...

Pasture development on cleared forest land has been investigated near Ilha de Maracá in northern Roraima, Brazil. Initial forest clearance and burning in the area is followed by short-term crop cultivation, and conversion to pasture based on introduced grasses such as Panicum maximum and Brachiaria humidicola. Derived pasture is initially productiv...

This paper considers the issue of geomorphological conservation. General concepts are illustrated by reference to a survey of the scientific importance of geomorphological features within the Nature Conservancy Council's Geological Conservation Review Oxfordness/Havergate site. The effects of coastal defence works on geomorphological processes are...

While the general geomorphological importance of coastal shingle systems may be the primary basis for their conservation, within-site management has often been guided by concern for the distinctive floras and faunas associated with the shingle. The present paper exemplifies the potential role of specific geomorphological criteria in conservation as...

A historical review is made of land degradation in the Yallahs River Basin, Jamaica, an area of steep slopes and highly dissected terrain. The contemporary persistence of land degradation is examined, and strategies for its amelioration suggested. -Authors

The stratigraphic significance of river terraces is discussed within the context of changing hydrological regimes in the Quaternary. A hypothetical example illustrates the complex relationship between environmental change, expressed in terms of geomorphological response, and river terrace stratigraphy. -Authors

In the British Quaternary, two post-Cromerian interglacials, the Hoxnian and the Ipswichian, are recognized. Evidence of additional interglacials in this interval is widely accepted in the oceanic record of Quaternary events, and the possibility that at least one additional interglacial of this age is represented in Britain has been discussed. Howe...

A semiquantitative method has been developed for the classification of lowland forest terrain in Colombian Amazonia. The method, which makes use of SLAR imagery at a scale of 1:200 000, is hierarchic in character and provides for the recognition of up to seven terrain classes. The morphological evolution of the landscape is discussed in the light o...

Sediments and an associated molluscan and ostracod fauna were exposed in 1974 in a temporary excavation at Fisherton, near Salisbury. The sections showed a chalk rubble at the base, overlain by terrace deposits of the River Nadder, comprising fluvial gravels below, and sandy clays with colluvial affinities above, from which the fauna was collected....

Roadworks associated with the M1 Motorway improvement in Hertfordshire revealed a sequence of four pre-Anglian depositional stages of the proto-Thames, and Anglian fluvioglacial gravels. The altitudinal relationships of the deposits are clearly demonstrated and the results reinforce the value of component ratios and roundness values in establishing...

Concerned with four gravels: the Higher Pebble Gravel, Westland Green Gravel, Higher Gravel Train and Lower Gravel Train. The far-travelled component peaks in the Westland Green gravel and then declines over time. There is also comment on the Chiltern drift. -K.Clayton

Pre-Anglian terrace stages of the proto-Thames system are traced from the present middle Thames area into Essex and south East Anglia. Gravel composition indicates that each of the main terrace stages is associated with an influx of far-travelled material, probably signifying at least three phases of pre-Anglian glaciation in the south Midlands. Gr...

Experimental plots were installed on seven sites (five field, one grassland and one rainforest) in the Colombian Amazonas region. Rainfall, runoff and sediment yield were recorded over a period of eight weeks. The grassland plot showed highest runoff but lowest sediment yield. Wide fluctuations of runoff were measured on the rainforest plot but sed...

The incidence of volcanic pebbles in the gravels of the middle Thames basin is noted. The detailed petrography of volcanic clasts at two sites is described and found to be broadly similar to that of material from sites in East Anglia, thought to be of Welsh origin. The frequency of volcanic pebbles in the two areas is also similar. This evidence su...

The Gravel Trains of the Thames have been examined in an area between Bourne End (Bucks) and Bricket Wood (Herts), and have been compared with gravels at higher and lower levels. Pebble lithology and the roundness of flint pebbles have been determined in the half-phi size range 11·2-16·0 mm. The Mann-Whitney U test is used to measure the significan...