How LCA studies deal with uncertainty

In recent years many workers have examined the implications of various sources of uncertainty for the reliability of Life Cycle Assessment (LCA). Indeed, the International Standardization Organization (ISO) has recognised the relevance of this work by including several cautionary statements in the ISO 14040 series of standards. However, in practice, there is a risk that the significance of these uncertainties for the results of an LCA could be overlooked as practitioners strive to complete studies on time and within budget. This paper presents the findings of a survey of LCA studies we made to determine the extent to which the problem of uncertainty had been dealt with in practice. This survey revealed that the significance of the limitations on the reliability of LCA results given in the standards has not been fully appreciated by practitioners. We conclude that the standards need to be revised to ensure that LCA studies include at least a qualitative discussion on all relevant aspects of uncertainty.     

Discounting and the environment should current impacts be weighted differently than impacts harming future generations?

Background  In Life-Cycle Assessment (LCA), decision makers are often faced with tradeoffs between current and future impacts. One typical example is waste incineration, where immediate emissions to the air from the incineration process have to be weighted against future emissions of slag landfills. Long-term impacts are either completely taken into account or they are entirely disregarded in case of a temporal cut-off. Temporal cutoffs are a special case of discounting. Objective  In this paper, discounting is defined as valuing damages differently at different points of time using a positive or negative discount rate. Apart from temporal cut-offs, discounting has rarely been applied in LCA so far. It is the goal of this paper to discuss the concept of discounting and its applicability in the context of LCA. Methods  For this purpose, we first review the arguments for discounting and its principles in economic sciences. Discounting in economics can be motivated by pure time preference, productivity of capital, diminishing marginal utility of consumption, and uncertainties. The nominal discount rate additionally includes changes in the price level. These arguments and their justification are discussed in the context of environmental impacts harming future generations. Results and Discussion  It is concluded that discounting across generations because of pure time preference contradicts fundamental ethical values and should therefore not be applied in LCA. However, it has to be acknowledged that in practice decision makers often use positive discount rates because of pure time preference — either because they might profit from imposing environmental damage on others instead of themselves or because people in the far future are not of immediate concern to them. Discounting because of the productivity of capital assumes a relationship between monetary values and environmental impact. If such a relationship is accepted, discounting could be applied. However, future generations should be compensated for the environmental damage. It is likely that they would demand a higher compensation if the real per capita income increases. As both the compensation and the discount rate are related to economic growth, the overall discount rate might be close to zero. It is shown that the overall discount rate might even be negative considering that the required compensation could increase (even to infinite) if natural assets remain scarce, whereas the utility of consumption diminishes with increasing income. Uncertainties could justify both positive and negative discount rates. Since the relationship between uncertainties and the magnitude of damage is generally not exponential, we recommend to model changes in the magnitude of damage in scenario analysis instead of considering it in discounting (which requires an exponential function of time in the case of a constant discount rate). We investigated the influence of discounting in a case study of heavy metal emissions from slag landfills. It could be shown that even small discount rates of less than 1 % lead to a significant reduction of the impact score, whereas negative discount rates inflate the results. Conclusions and Recommendations  Discounting is only applicable when temporally differentiated data is available. In some cases, such a temporal differentiation is necessary to take sound decisions, especially when long emission periods are involved. An example is the disposal of nuclear or heavy metal-containing waste. In these cases, the results might completely depend on the discount rate. This paper helps to structure arguments and thus to support the decision about whether or not discounting should be applied in an LCA.     

Effects of sand bar openings on some limnological variables in a hypertrophic tropical coastal lagoon of Brazil

This study describes the spatial and temporal dynamics of several physical, chemical and biological variables in the Grussai lagoon, and their relationship to ephemeral sand bar openings and to a constant in natura waste water input. The spatial variation in pH, dissolved oxygen, electrical conductivity, total alkalinity and nutrients (e.g. soluble reactive silicate, soluble reactive phosphate and ammonium) was associated to the anoxic and nutrient rich groundwater discharge, the development of aquatic macrophytes, the biological activities of phytoplanktonic community and the marine influence. During the period when the sand bar was closed (isolated), the lagoon water was supersaturated with dissolved oxygen and exhibited high values of pH (8–10), total alkalinity (3.000–5.000 μeq l^-1), and chlorophyll a contents (60-300 μg l^-1), and had low values of dissolved nutrients (nearly undetectable). These suggest a biological processes dominance. When the sand bar was opened, there was an enrichment with dissolved inorganic nutrients (e.g. ammonium and soluble reactive phosphorus up to 120 and 5 μM, respectively) and a decrease in pH (below 8), total alkalinity (below 3.000 μeq l^-1) and dissolved oxygen during the initial second to eight days. Subsequently there was a period when the physical and chemical characteristics of seawater prevailed. The lagoon returned chemical to the pre-opening water conditions in a few days (∼ 10–20). This quick return implies highly efficient biological mechanisms. The high levels of chlorophyll a, total nitrogen and phosphorus in the water column indicate a high eutrophication stage in the Grussai lagoon during the sand bar closed periods. This revised version was published online in July 2006 with corrections to the Cover Date.     

EVIDENCE FOR IMPACTS OF NONINDIGENOUS MACROALGAE: A META‐ANALYSIS OF EXPERIMENTAL FIELD STUDIES1

Invasions by nonindigenous macroalgal species (NIMS) potentially cause severe impacts on native species. We conducted a meta‐analysis of 18 field‐based manipulative experiments to quantify the direction and magnitude of impacts (Hedges effect size d, hereafter ES). We found significant small‐to‐medium negative effects on “macrophyte abundance” (cover, biomass of native taxa; ES_cumulative = ?0.30) and medium‐to‐large negative effects on “macrophyte assemblages” (richness, diversity, total abundance; ES_cumulative = ?0.70). In contrast, ES_cumulative were not significant for “macrophyte processes” (growth, mortality; ES_cumulative = ?0.39), “animal abundance” (densities; ES_cumulative = ?0.13), or “animal assemblages” (richness, diversity; ES_cumulative = 0.75). The nonsignificant effect sizes were characterized by low sample sizes and should be interpreted with caution. Three study‐specific effect sizes were particularly large (cumulative are likely biased toward larger effects because only the most conspicuous NIMS have been tested and because nonsignificant results are less likely to be published. To better understand the impacts of NIMS, more manipulative experiments are needed, testing more species and under contrasting environmental conditions. Future studies should include procedural control treatments and report the abundance of the NIMS to avoid ambiguous interpretations. In conclusion, current experimental evidence shows that NIMS have, on average, small‐to‐large negative impacts on native plant species and assemblages. It is possible that these effects can result in severe consequences when accumulated over long time periods and large spatial scales.     

Climate change increases risk of fusarium ear blight on wheat in central China

To estimate potential impact of climate change on wheat fusarium ear blight (FEB), simulated weather for the A1B climate change scenario was input into a model for estimating FEB in central China. In this article, a logistic weather‐based regression model for estimating incidence of wheat FEB in central China was developed, using up to 10 years (2001–2010) of disease, anthesis date and weather data available for 10 locations in Anhui and Hubei provinces. In the model, the weather variables were defined with respect to the anthesis date for each location in each year. The model suggested that incidence of FEB is related to number of days of rainfall in a 30‐day period after anthesis and that high temperatures before anthesis increase the incidence of disease. Validation was done to test whether this relationship was satisfied for another five locations in Anhui province with FEB data for 4–5 years but no nearby weather data, using simulated weather data obtained employing the regional climate modelling system PRECIS. How climate change may affect wheat anthesis date and FEB in central China was investigated for period 2020–2050 using wheat growth model Sirius and climate data simulated using PRECIS. The projection suggested that wheat anthesis dates will generally be earlier and FEB incidence will increase substantially for most locations.     

Above ground perennial plant biomass across an altitudinal and land-use gradient in Namaqualand,South Africa

This study set out to generate estimates of the standing perennial biomass for six different vegetation types, and associated upland and lowland habitats, across the altitudinal gradient presented by the Kamiesberg mountain range in the Namaqualand region of the Northern Cape Province of South Africa. Volume-biomass regressions, established for 94 perennial species accounting for 70–80% of the plant cover, were used to generate these estimations. Comparisons to other studies give similar findings, corroborating the method adopted. Biomass was found to vary significantly in relation to the altitudinal, and associated rainfall, gradient, as well as by habitat type where the rocky uplands have considerably more biomass that the sandy lowland habitats. An examination of the impact of sustained heavy grazing associated with a communal rangeland on this standing perennial biomass, showed a significant decrease in on the lowland habitats. This loss in biomass is principally of palatable species, with no evidence of a response in terms of perennial biomass. These findings point to degradation on the lowland habitats of the communal rangeland, with negative consequences for livestock farmers in the region.     

The Impacts of Household Consumption and Options for Change

This introductory article situates the contributions that comprise this special issue within the field of sustainable consumption and production (SCP) studies. After a brief review of the policy history surrounding SCP, we organize our discussion and the subsequent collection of articles into two groups. The first suite of articles views the environmental impacts associated with household consumption from the perspectives of different consumer groups, income levels, and geographic areas. This work confirms and refines several insights that have been developing over the past several years, namely that food and beverages, mobility, housing, and energy-using products are the most critical consumption domains from the standpoint of environmental sustainability and that higher household income leads to greater (but less than proportional) impacts. The second subset of articles analyzes the potential for mitigating these impacts through behavioral changes and innovation strategies. Although the contributions to this special issue describe several noteworthy examples of information- and team-based initiatives to catalyze behavioral changes, the state of knowledge pertaining to this aspect of the consumption problem is much more inchoate. Research on the formulation and implementation of effective "change management for sustainable consumption" should be treated as an area of priority attention for industrial ecologists.     

Off-Highway Vehicle Trail Impacts on Breeding Songbirds in Northeastern California

Abstract: Rapid growth in off-highway vehicle (OHV) use in North America leads to concerns about potential impacts on wildlife populations. We studied the relationship between distance to active OHV trail and songbird nesting success and abundance in northeastern California, USA, from 2002 to 2004. We found evidence of greater nest desertion and abandonment and reduced predation on shrub nests <100 m from OHV trails than at nests >100 m from OHV trails. Two of 18 species studied were less abundant at sites on trails than at sites 250 m from trails, and no species were more abundant on trails. Management of OHV trail development should consider possible negative impacts on nesting success and abundance of breeding birds.