Runoff and sediment losses from 27 upland catchments in Southeast Asia: Impact of rapid land use changes and conservation practices

Rapid changes in upland farming systems in Southeast Asia generated predominantly by increased population pressure and ‘market forces’ have resulted in widespread land degradation that has been well documented at the plot scale. Yet, the links between agricultural activities in the uplands and downstream off-site effects remain largely unknown because of the difficulties in transferring results from plots to a larger scale. Many authors have thus pointed out the need for long-term catchment studies. The objective of this paper is to summarize the results obtained by the Management of Soil Erosion Consortium (MSEC) over the last 5 years from 27 catchments in five countries (Indonesia, Laos, Philippines, Thailand, and Vietnam). The purpose of the study was to assess the impacts of cultivation practices on annual runoff and erosion rates. Initial surveys in each catchment included topography, soils and land use. Monitoring included climatic, hydrologic and erosion (total sediment yield including bed load and suspended sediment load) data, land use and crop yields, and farmers’ income. In addition, new land management options were introduced through consultations with farmers and evaluated in terms of runoff and erosion. These included tree plantations, fruit trees, improved fallow with legumes, maize intercropped with legumes, planted fodder, native grass strips and agro-ecological practices (direct sowing and mulch-based conservation agriculture). Regressions analyses showed that runoff during the rainy season, and normalized runoff flow coefficient based on erosive rainfall during the rainy season (rainfall with intensity exceeding 25 mm h⁻¹) increase with the percentage of the catchment covered by maize. Both variables decrease with increasing soil depth, standard deviation of catchment slope (that reflects terrain roughness), and the percentages of the catchment covered by fallow (regular and improved), tree plantations and planted fodder. The best predictors of sediment yield were the surface percentages of maize, Job's tears, cassava and footpaths. The main conclusions generated from this study were: (i) soil erosion is predominantly influenced by land use rather than environmental characteristics not only at the plot scale but also at the catchment scale; (ii) slash-and-burn shifting cultivation with sufficiently long rotations (1 year of cultivation, 8 years of fallow) is too often unjustly blamed for degradation; (iii) in its place, continuous cropping of maize and cassava promotes high rates of soil erosion at the catchment scale; (iv) conservation technologies are efficient in reducing runoff and total sediment yield at the catchment scale; (v) the adoption of improved soil management technologies by upland farmers is not a function of the degree of intensification of their farming system and/or of their incomes. The results suggest that if expansion of maize and cassava into already degraded upland systems were to occur due to increased demand for biofuels, there is a risk of higher runoff and sediment generation. A failure to adopt appropriate land use management strategies will result in further rapid resource degradation with negative impacts to downstream communities.     

A new approach to assessment and management of the impact from medical liquid radioactive waste

The Swedish regulations concerning disposal of clinical radioactive waste are currently under revision and a graded approach is proposed for risk limitation purposes. To assist the revision procedures, a screening study was performed to estimate public exposures from liquid releases from hospitals to public sewers. The results showed that doses to sewage workers were above the dose constraint of 100muSva(-1) especially for (131)I and (99m)Tc. Hence, a dynamic model, LUCIA, was developed for realistic assessments in which radionuclide transportation in sewers was modelled. Probabilistic simulations were performed to obtain probability distributions of radionuclide concentrations in sludge. Concurrently, estimates of the effective doses to sewage workers decreased significantly and were below 10muSva(-1) except for (111)In and (131)I. However, the Kd-coefficients representing the partition of radioactivity between water and sludge in sewers are highly uncertain for (111)In. As shown by sensitivity studies, these values are the major determinant of the exposures in sewers.     

Calibration of a portable HPGe detector using MCNP code for the determination of 137Cs in soils

In situ gamma spectrometry provides a fast method to determine (137)Cs inventories in soils. To improve the accuracy of the estimates, one can use not only the information on the photopeak count rates but also on the peak to forward-scatter ratios. Before applying this procedure to field measurements, a calibration including several experimental simulations must be carried out in the laboratory. In this paper it is shown that Monte Carlo methods are a valuable tool to minimize the number of experimental measurements needed for the calibration.     

Speciation and long- and short-term molecular-level dynamics of soil organic sulfur studied by X-ray absorption near-edge structure spectroscopy

We investigated speciation, oxidative state changes, and long- and short-term molecular-level dynamics of organic S after 365 d of aerobic incubation with and without the addition of sugarcane residue using XANES spectroscopy. Soil samples were collected from the upper 15 cm of undisturbed grasslands since 1880, from undisturbed grasslands since 1931, and from cultivated fields since 1880 in the western United States. We found three distinct groups of organosulfur compounds in these grassland-derived soils: (i) strongly reduced (S to S) organic S that encompasses thiols, monosulfides, disulfides, polysulfides, and thiophenes; (ii) organic S in intermediate oxidation (S to S) states, which include sulfoxides and sulfonates; and (iii) strongly oxidized (S) organic S, which comprises ester-SO-S. The first two groups represent S directly linked to C and accounted for 80% of the total organic S detected by XANES from the undisturbed soils. Aerobic incubation without the addition of sugarcane residue led to a 21% decline in organanosulfur compounds directly linked to C and to up to an 82% increase inorganic S directly bonded to O. Among the C-bonded S compounds, low-valence thiols, sulfides, thiophenic S, and intermediate-valence sulfoxide S seem to be highly susceptible to microbial attack and may represent the most reactive components of organic S pool in these grassland soils. Sulfonate S exhibited a much lower short-term reactivity. The incorporation of sugarcane residue resulted in an increase in organosulfur compounds directly bonded to C at the early stage of incubation. However, similar to soils incubated without residue addition, the proportion of organic S directly linked to C continued to decline with increasing duration of aerobic incubation, whereas the proportion of organic S directly bonded to O showed a steady rise.     

Putting the cart before the horse: Water governance and IWRM

Water governance has emerged as perhaps the most important topic of the international water community in the 21^st century, and achieving “good” water governance is now a focus of both policy discourse and innumerable development projects. Somewhat surprisingly in light of this attention, there is widespread confusion about the meaning of the term “water governance”. This paper reviews the history of the term's use and misuse to reveal how the concept is frequently inflated to include issues that go well beyond governance. Further, it highlights how calls to improve water governance often espouse predetermined goals that should instead be the very function of water governance to define. To help overcome this confusion, the paper suggests a more refined definition of water governance and related qualities of good water governance that are consistent with broader notions of the concepts. In light of the substantial resources allocated in its name, this paper's findings show there is significant potential to strengthen efforts at improving water governance.     

Ethnobotany and ecological perspectives on the management and use of plant species for a traditional fishing trap, southern coast of São Paulo, Brazil

The cerco-fixo is an artisanal fishing trap widely used by traditional communities in the estuarine region of the southern coast of the state of São Paulo, Brazil. The primary goal of the study was to investigate, through ethnobotanical and ecological approaches, the use of plant species by traditional fishermen to build the cerco-fixo at Cardoso Island State Park and Cananéia Island. Ethnobotanical data were collected through interviews, direct observation, plant collection and identification, and document analysis. An ecological evaluation was also done comparing five 20 × 20 m plots in a managed area to five 20 × 20m plots in an unmanaged area, both within arboreal sandy soil vegetation called restinga arbórea, found within the Brazilian Atlantic Forest domain. This study involved 34 fishermen living at Cardoso and Cananéia Islands. The fishermen know more than 90 Atlantic Forest plant species that can be used to build the cerco-fixo. Tree species from the family Myrtaceae were the most quoted in the interviews. With respect to the ecological evaluation, the cluster analyses showed greater heterogeneity in terms of floristic composition (i.e. greater floristic dissimilarity) within the plots of the managed area. The analyses of diversity showed a slightly higher species richness and slightly lower values for Shannon, Simpson, Hurlbert’s PIE and Evenness indices in the managed area (59 species; H′ = 3.28; 1/D = 10.77; E = 0.80; Hurlbert’s PIE = 0.91) compared to the unmanaged area (54 species; H′ = 3.39; 1/D = 20.21; E = 0.85; Hurlbert’s PIE = 0.95). The Hutcheson’s t test showed no significant difference between both areas’ Shannon diversity indices (t: −1.04; p: 0.30). These results are attributed to the greater dominance of the palm species Euterpe edulis Mart. in the managed area (28.2% of the trees sampled at this area; n = 118), which equals twice the percentage of individuals of the same species found for the unmanaged area (14.6% of the sampled trees; n = 48). We discuss the impact of the fishermen’s harvesting practices in the managed area with an emphasis on three main points: (1) the harvesting practices are likely not contributing to a decrease in diversity in the managed area; (2) the greater heterogeneity in terms of floristic composition found for the managed area may reflect a mosaic pattern created by the opening of small tree-gaps distributed across this area over the course of more than 50 years; (3) the disturbance promoted by the fishermen’s harvesting practices can be compared to natural disturbances of low impact that create mosaic patterns in tropical forests. This study emphasizes the prominence of the human dimension in ecological processes and the importance of considering the perspectives of local people when discussing the conservation of the natural environments in which these people live.     

A harvest failure approach to assess the threat from an invasive species

We present the idea of using potential infringements on annual allowable harvest targets as an approach to estimate threats from invasive species to the forest products sector. The approach uses present-day harvest levels as a reference level to estimate when and where the impact of a nonnative forest pest could become economically damaging. We use a generic model that simulates spread and damage by nonnative invasive species, basic harvest and forest growth through time. The concept is illustrated with a case study of a new nonnative invasive pest, Sirex noctilio Fabricius on pine resources in eastern Canada. Impacts of invasion on wood supply, in particular, the point at which present-day harvest levels are not attainable, were identified for 77 non-overlapping geographical regions that delimit the primary wood supply areas around large mills and wood processing facilities in eastern Canada. The results identify the minimum area of a pest outbreak that could trigger harvest shortages (approximately 12.5–14 M ha of pine forests in Ontario and Quebec). Beyond this level, the amount of host resource available for harvesting in any given year declines rapidly. The failure to sustain broad-scale harvest targets may be an attractive and intuitive indicator for policy makers and regulators interested in developing control and “slow-the-spread” programs for non-native forest pests.     

An unconventional method for the recovery of caustic soda from spent Al-rich pickling solutions

This work presents an unconventional procedure for the recovery of spent Al-rich caustic soda solutions from the pickling of dies for the production of aluminium extrusions. Caustic soda was regenerated at roughly 70%, by precipitating aluminate, after addition of a silica source, in the form of zeolite A, a microporous material that is widely used in many technological sectors. It was shown that the process is reliable and can be repeated for several cycles, provided the concentration of the caustic soda solution is suitably restored. The by-product obtained, zeolite A, proved to be a high-grade material with performance as a cation exchanger and physical sorbent that is certainly comparable to that reported in literature (e.g., cation exchange capacity equal to 5.14 meq g(-1) vs. 5.48 meq g(-1) and water vapour adsorption capacity of 26.5% vs. 27.6% at 16 torr and 298 K). The economics of the process, although not examined yet, would appear generally favourable, considering that zeolite A is a valuable by-product which widely covers the costs for the recovery of the spent solutions. There are, therefore, significant prospects for the use of zeolite A, particularly as a builder in detergent formulation.     

Economic analysis of conventional versus selective demolition—A case study

Studies on selective demolition (also named deconstruction) in the past few years have produced some high quality economic, material and environmental information. Economic data, however, varies considerably between regions since local conditions strongly influence labour costs, tipping fees and/or market prices for recovered materials. Regional financial and regulatory constraints will bind the economic viability of conventional and selective demolition choices, which are essentially economic in a free market. Given this, the present study evaluates the economic implications of the two demolition types by analyzing a case study in Portugal. A few scenarios are considered, based on possible waste management options, some of which favour selective demolition over the conventional type.