The contributions of C. F. Charter to tropical soil survey and classification

Cecil Charter had taught botany and biology in China and Antigua for five years, when in 1931 he was engaged to conduct a soil survey of the sugarcane-growing areas of Antigua. This was followed by similar surveys elsewhere in the Caribbean. In 1944, he joined the West African Cacao Research Institute in the Gold Coast (now Ghana) to carry out soil investigations in the forest zones of West Africa. In 1949 he moved to organise the soil survey unit in the Gold Coast Department of Agriculture, and, in 1951, to found and direct the new Soil and Land Use Survey Department. He rapidly built up a highly professional unit that produced many practical and useful reports of high quality. He based the surveys on ecological principles, selecting river basins as mapping regions. In the initial absence of qualified soil scientists, he subdivided the soil survey process and trained school leavers as technicians for separate tasks. Teams of these technicians examined soils, vegetation and land use at regular intervals on regularly-spaced traverses cut across the topography. Charter’s contributions to soil science included his recognition of non-residual tropical soils formed in material brought to the surface by soil fauna and treefall. Also, he differentiated between highly acidic upland Oxysols in high-rainfall areas, which he considered unsuitable for cocoa cultivation, and less acidic Ochrosols, which were more suitable. Based on farmers’ experience and his ecological background, he differentiated between forest, thicket and savannah soils within these groups. He strongly advocated genetic and contextual classification of tropical soils

Bangladesh’s dynamic coastal regions and sea-level rise

The physical geography of Bangladesh’s coastal area is more diverse and dynamic than is generally recognised. Failure to recognise this has led to serious misconceptions about the potential impacts of a rising sea-level on Bangladesh with global warming. This situation has been aggravated by accounts giving incorrect information on current rates of coastal erosion and land subsidence. This paper describes physical conditions within individual physiographic regions in Bangladesh’s coastal area based on ground-surveyed information, and it reviews possible area-specific mitigation measures to counter predicted rates of sea-level rise in the 21st century. Two important conclusions are drawn: the adoption of appropriate measures based on knowledge of the physical geography of potentially-affected areas could significantly reduce the currently-predicted displacement of many millions of people; and the impacts of a slowly-rising sea-level are currently much less than those generated by rapidly increasing population pressure on Bangladesh’s available land and water resources and by exposure to existing environmental hazards, and the latter problems need priority attention

The historical avulsion of the Tista River, and its relationship to the Brahmaputra: Map and archive evidence from 1750 to 1835

Alluvial fans are constructed when river deposition raises local elevations until the river “avulses” to an alternative lower elevation alignment. Avulsions may be triggered by exogenous events, such as floods that locally overtop the river’s banks; they may then cause extreme flooding on a fan and have major impacts. Rivers draining the Himalayas into the Gangetic plain have behaved historically in this way; for example, the Kosi River’s historical westward migration (1731–1963), and its recent eastward shift (1980). In the major fan‐delta of the Bengal Basin, the Brahmaputra and its tributary, the Tista, have both undergone historical avulsions, with some suggestion that these may have been causally linked. Between the Rennell survey of Bengal (1765–77) and the partial re‐survey by Wilcox and Ommanney (1828–35), the Brahmaputra River substantially changed its course. In Rennell’s time it turned south‐east into the Sylhet Basin leaving the higher land of the Madhupur Tract on its right; by 1830, it flowed due south with the Tract on its left. One hypothesis for the timing and cause of this avulsion relates it to the impact of a major flood and avulsion in the River Tista in 1787. This paper examines the evidence of the Rennell maps, the East India Company archives of correspondence between District Collectors about flooding and avulsion in the Tista, and the diaries of Francis Hamilton Buchanan who travelled along the Tista in 1807–11. From these contemporary sources it is possible to re‐construct the changes in the River Tista in the late 18th century, and to conclude that its avulsion had little direct influence on that of the Brahmaputra, although it went through some radical rearrangements of its own

Variation in Rice Cadmium Related to Human Exposure

Cereal grains are the dominant source of cadmium in the human diet, with rice being to the fore. Here we explore the effect of geographic, genetic, and processing (milling) factors on rice grain cadmium and rice consumption rates that lead to dietary variance in cadmium intake. From a survey of 12 countries on four continents, cadmium levels in rice grain were the highest in Bangladesh and Sri Lanka, with both these countries also having high <i>per capita</i> rice intakes. For Bangladesh and Sri Lanka, there was high weekly intake of cadmium from rice, leading to intakes deemed unsafe by international and national regulators. While genetic variance, and to a lesser extent milling, provide strategies for reducing cadmium in rice, caution has to be used, as there is environmental regulation as well as genetic regulation of cadmium accumulation within rice grains. For countries that import rice, grain cadmium can be controlled by where that rice is sourced, but for countries with subsistence rice economies that have high levels of cadmium in rice grain, agronomic and breeding strategies are required to lower grain cadmium

Organic Matter-Solid Phase Interactions Are Critical for Predicting Arsenic Release and Plant Uptake in Bangladesh Paddy Soils

Agroecological zones within Bangladesh with low levels of arsenic in groundwater and soils produce rice that is high in arsenic with respect to other producing regions of the globe. Little is known about arsenic cycling in these soils and the labile fractions relevant for plant uptake when flooded. Soil porewater dynamics of field soils (n = 39) were recreated under standardized laboratory conditions to investigate the mobility and interplay of arsenic, Fe, Si, C, and other elements, in relation to rice grain element composition, using the dynamic sampling technique diffusive gradients in thin films (DGT). Based on a simple model using only labile DGT measured arsenic and dissolved organic carbon (DOC), concentrations of arsenic in Aman (Monsoon season) rice grain were predicted reliably. DOC was the strongest determinant of arsenic solid-solution phase partitioning, while arsenic release to the soil porewater was shown to be decoupled from that of Fe. This study demonstrates the dual importance of organic matter (OM), in terms of enhancing arsenic release from soils, while reducing bioavailability by sequestering arsenic in solution