Global Change Abstracts The Swiss Contribution - SCNAT

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206 Global Change Abstracts – The Swiss Contribution | General Topics 08.1-446 Restoring dense vegetation can slow mountain erosion to near natural benchmark levels Vanacker V, von Blanckenburg F, Govers G, Molina A, Poesen J, Deckers J, Kubik P W Germany, Belgium, Switzerland Geomorphology , Geology , Agriculture, Soil Sciences Tropical mountain areas may undergo rapid land degradation as demographic growth and intensified agriculture cause more people to migrate to fragile ecosystems. To assess the extent of the resulting damage, an erosion rate benchmark against which changes in erosion can be evaluated is required. Benchmarks reflecting natural erosion rates are usually not provided by conventional sediment fluxes, which are often biased due to modern land use change, and also miss large, episodic events within the measuring period. To overcome this, we combined three independent assessment tools in the southern Ecuadorian Andes, an area that is severely affected by soil erosion. First, denudation rates from cosmogenic nuclides in river sediment average over time periods of 1-100 k.y. and establish a natural benchmark of only 150 +/- 100 t km(-2) yr(-1). Second, we find that land use practices have increased modern sediment yields as derived from reservoir sedimentation rates, which average over periods of 10-100 yr to as much as 15 x 10(3) t km(-2)yr(-1). Third, our land cover analysis has shown us that vegetation cover exerts first-order control over present-day erosion rates at the catchment scale. Areas with high vegetation density erode at rates that are characteristically similar to those of the natural benchmark, regardless of whether the type of vegetation is native or anthropogenic. Therefore, our data suggest that even in steep mountain environments sediment fluxes can slow to near their natural benchmark levels with suitable revegetation programs. A set of techniques is now in place to evaluate the effectiveness of erosion mitigation strategies. Geology, 2007, V35, N4, APR, pp 303-306. 08.1-447 Wooden building products in comparative LCA Werner F, Richter K Switzerland Engineering , Energy & Fuels Background, Aim and Scope. We revised the results of approx. 20 years of international research on the environmental impact of the life cycle of wood products used in the building sector compared to functionally equivalent products from other materials. Main Features. Original studies either technical reports or scientific papers in English or German were considered. This literature was obtained via an extensive literature review (February 2006), via a consultation of compilations of life cycle assessments (LCA) of wood products (e.g. elaborated during the COST action E9) and from secondary literature. The resulting list of literature is considered to be quite complete and therefore covers the most relevant original comparative LCA studies of wood products in the building sector in Europe, Northern America and Australia. The documentation of the studies differs considerably in terms of completeness (life cycle stages included, assessment methods), transparency (description of methodological assumptions, characteristics of the products, available data, etc.) and scientific rigor (e.g. related to the functional equivalency). All encountered original studies are cited and their scope and transparency is shortly described. For the environmental ranking of wood products compared to functionally equivalent products, only quantitative, transparently described studies with no obvious methodological flaws were included, preferably covering the whole life cycle and conducted according to the ISO series of standards 14’040ff. For the assessment, the contribution of each product to an impact category was compared to the mean of all functionally equivalent products included in a study. Results and Discussion. Among the most important results are: fossil fuel consumption, potential contributions to the greenhouse effect and quantities of solid waste tend to be minor for wood products compared to competing products; impregnated wood products tend to be more critical than comparative products with respect to toxicological effects and/or photosmog depending on the type of preservative; incineration of wood products can cause higher impacts of acidification and eutrophication than other products, whereas thermal energy can be recovered; although composed wood products such as particle board or fibreboard make use of a larger share of wood of a tree compared to products out of solid wood, there is a high consumption of fossil energy associated with the production of fibres and particles/chips as well as with the production of glues, resins, etc. In LCAs of whole buildings, the materials used outside the areas of applicability of wood dominate the environmental profile of the building; current methods used for the impact assessment do not allow to consider (also favourable) impacts of forests, such as land occupation, impacts on biodiversity, purification of air, etc. Conclusions. Wood products that have been installed and are used in an appropriate way
Global Change Abstracts – The Swiss Contribution | General Topics tend to have a favourable environmental profile compared to functionally equivalent products from other materials. For the dispersion and application of these conclusions, it is necessary to adapt LCA to a form, which can be used on a regular basis for the decision making of different actors in the construction sector. Perspectives. LCA methodology in general (the series of standards ISO 14’040ff) and for the environmental assessment of wood products in particular have been developed and consolidated considerably in Europe and Northern America during the last decade; the more and more representative and reliable LCI data for wood products and competing products has become available. For the future use of the environmental value of wood products within sustainable development, the general perception of the beneficiary use of wood products has to be increased at various stages of decision-making. International Journal of Life Cycle Assessment, 2007, V12, N7, NOV, pp 470-479. 207
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