Good, bad or 'necessary evil'? Reinterpreting the colonial burning experiments in the savanna landscapes of West Africa

A simple ecological model underlies contemporary fire policy in many West African countries. The model holds that the timing (or seasonality) of annual savanna fires is a principal determinant of vegetation cover. The model's origin can be traced to the ideas held by influential colonial scientists who viewed anthropogenic fire as a prime force of regional environmental degradation. The main evidence in support of the model derives from the results of a series of long-term burning experiments carried out during last century. The experimental results have been repeatedly mapped onto fire policy often taking the form of a three-tiered model in which fire exclusion is considered the ultimate management objective, late dry-season fire is discouraged and early dry-season fire is allowed but only under specific, often state-controlled circumstances. This paper provides a critique of contemporary fire policy in the region and the fire ecology model on which it is based. Through an analysis of burn scars for the 2002–3 fire season generated from ETM+ imagery, the study documents the spatiotemporal pattern of burning for an area in southern Mali. It argues that current policy, which is informed by an a-spatial model, cannot adequately account for the critical pattern of burning that is characteristic of the region. A reinterpretation of the burning experiments is presented in light of four factors: empirical data; recent developments in patch-mosaic theory; historical evidence on the effects of fire suppression; and data on indigenous burning strategies, all of which suggest a need to reconsider current fire policy.     

Separated by common ground? Bringing (post)development and (post)colonialism together

The relationship between mainstream development policy (and perhaps also development studies) and postcolonial theorists has often been characterized as a dialogue of the deaf. Rather like in the old 'debates' between adherents of modernization and neo-Marxist theories, the protagonists are often thought to be talking at or past one another, rather than with each other. This paper reassesses some firmly held views on both sides of the schism. On the one hand, many official development agencies appear to promote business as usual (often quite literally, as a recent War on Want report attests in the case of the UK's DFID using its aid budget to promote profitable opportunities for British corporations). On the other hand, some postcolonial purists rely on surprisingly modernist, totalizing discursive techniques while claiming post-structural credentials, or baulk at the prospects of practical engagement. Discrepancies between theory, discourse, policy and practice are not the preserve of one side. However, the middle ground is firmer and better trodden than most believe. Considerable progress has been made and the paper assesses examples of productive engagement and concludes with suggestions for carrying forward the challenges.     

Lithofacies and origin of late Quaternary mass transport deposits in submarine canyons, central Scotian Slope, Canada

Mass transport deposits, up to 3·9 m thick, have been identified from piston cores collected from canyon floors and inter-canyon ridges on the central Scotian Slope. These deposits are characterized by four distinct mass-transport facies – folded mud, dipping stratified mud, various types of mud-clast conglomerate, and diamicton. Commonly, the folded and stratified mud facies are overlain by mud-clast conglomerate, followed by diamicton and then by turbidity current deposits of well-sorted sand. Stratified and folded mud facies were sourced from canyon walls. Overconsolidation in clasts in some mud-clast conglomerates indicates that the source sediment was buried 12–33 m, much deeper than the present cored depth, implying a source in canyon heads and canyon walls. The known stratigraphic framework for the region and new radiocarbon dating suggests that there were four or five episodes of sediment failure within the past 17 ka, most of which are found in more than one canyon system. The most likely mechanism for triggering occasional, synchronous failures in separate canyons is seismic ground shaking. The facies sequence is interpreted as resulting from local slides being overlain by mud-clast conglomerate deposits derived from failures farther upslope and finally by coarser-grained deposits resulting from retrogressive failure re-mobilizing upper slope sediments to form debrisflows and turbidity currents.     

HYDROLOGY AND GEOMORPHIC EFFECTS OF A HIGH-MAGNITUDE FLOOD IN AN ALPINE RIVER

The catchment of the River Partnach, a torrent situated in a glacial valley in the Northern Calcareous Alps of Bavaria/Germany, was affected by a high‐magnitude flood on 22/23 August 2005 with a peak discharge of more than 16 m³s^‐1 at the spring and about 50 m³s^‐1 at the catchment outlet. This flood was caused by a long period of intense rainfall with a maximum intensity of 230 mm per day. During this event, a landslide dam, which previously held a small lake, failed. The flood wave originating from the dam breach transported a large volume of sediment (more than 50 000 m³) derived from bank erosion and the massive undercutting of a talus cone. This caused a fundamental transformation of the downstream channel system including the redistribution of large woody debris and channel switching. Using terrestrial survey and aerial photography, erosional and depositional consequences of the event were mapped, pre‐ and post‐event surfaces were compared and the sediment budget of the event calculated for ten consecutive channel reaches downstream of the former lake. According to the calculations more than 100 000 tonnes of sediment were eroded, 75% of which was redeposited within the channel and the proximal floodplain. A previous large flood which occurred a few weeks prior to the August 2005 event had a significant effect on controlling the impact of this event.     

Effects of basin size on low-flow stream chemistry and subsurface contact time in the Neversink River watershed,New York

The effects of basin size on low-flow stream chemistry and subsurface contact time were examined for a part of the Neversink River watershed in southern New York State. Acid neutralizing capacity (ANC), the sum of base cation concentrations (SBC), pH and concentrations of total aluminum (Al), dissolved organic carbon (DOC) and silicon (Si) were measured during low stream flow at the outlets of nested basins ranging in size from 0·2 to 166·3 km². ANC, SBC, pH, Al and DOC showed pronounced changes as basin size increased from 0·2 to 3 km², but relatively small variations were observed as basin size increased beyond 3 km². An index of subsurface contact time computed from basin topography and soil hydraulic conductivity also showed pronounced changes as basin size increased from 0·2 to 3 km² and smaller changes as basin size increased beyond 3 km². These results suggest that basin size affects low-flow stream chemistry because of the effects of basin size on subsurface contact time. © 1997 John Wiley & Sons, Ltd.