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Characterization factors for water consumption and
greenhouse gas emissions based on freshwater fish
species extinction
Marlia M. Hanafiah§¥, Marguerite A. XenopoulosStephan Pfistei#, Rob S.E. W. Leuven§,
Mark A.J. Huijbregts §
^Department of Environmental Science, Institute for Water and Wetland Research, Radboud
University Nijmegen, Nijmegen, The Netherlands
^Department o f Environmental Science, National University of Malaysia, 43600 UKM Bangi,
Selangor, Malaysia
^Department of Biology, Trent University, Peterborough, Ontario, K9J 7B8, Canada
#ETH Zurich, Institute of Environmental Engineering, 8093 Zurich, Switzerland
Corresponding author e-mail: M.Huijbregts@science.ru.nl; phone: +31-243652835
This document is the unedited Author’s version of a Submitted W ork that was
subsequently accepted for publication in Environmental Science & Technology,
copyright © American Chemical Society after peer review. To access the final edited and
published w ork see http://pubs.acs.org/doi/abs/10.1021/es1039634.
Abstract
Human-induced changes in water consumption and global warming are likely to reduce the
species richness of freshwater ecosystems. So far, these impacts have not been addressed in
the context of life cycle assessment (LCA). Here, we derived characterization factors for
water consumption and global warming based on freshwater fish species loss. Calculation of
characterization factors for potential freshwater fish losses from water consumption were
estimated using a generic species-river discharge curve for 214 global river basins. We also
derived characterization factors for potential freshwater fish species losses per unit of
greenhouse gas emission. Based on five global climate scenarios, characterization factors for
63 greenhouse gas emissions were calculated. Depending on the river considered,
characterization factors for water consumption can differ up to 3 orders of magnitude.
Characterization factors for greenhouse gas emissions can vary up to 5 orders of magnitude,
depending on the atmospheric residence time and radiative forcing efficiency of greenhouse
gas emissions. An emission of 1 ton of CO2 is expected to cause the same impact on potential
fish species disappearance as the water consumption of 10-1000 m3, depending on the river
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basin considered. Our results make it possible to compare the impact of water consumption
with greenhouse gas emissions.
Keywords: water consumption, global warming, life cycle assessment, freshwater ecosystems
Brief: Development of a life cycle impact assessment method to address effects of water
consumption and greenhouse gas emissions on freshwater fish species disappearance.
Introduction
Life cycle assessment (LCA) is a technique used to assess the environmental impacts
associated with a product, process or service.1 This paper focuses on life cycle impact
assessment (LCIA), the phase where inventory data are assessed in terms of environmental
impacts. Impact categories in LCIA can be associated with areas of protection (AoPs), such as
natural resources, ecosystem quality and human health.2 The relationship between inventory
data and the magnitude of impacts on the AoPs in LCIA are expressed in terms of
characterization factors.3
Global freshwater biodiversity is one of the AoPs which has experienced large adverse
effects.4 Although freshwater fish species losses due to anthropogenic impacts have been
addressed in earlier studies,5-7 less attention has been paid to assessing these impacts in an
LCA perspective.8 At present, freshwater-related studies using LCA techniques have mostly
focused on toxicological effects.3,9-11 The environmental impacts of water consumption on
terrestrial ecosystems has only recently been conducted by Pfister et al.12 Impacts of water
consumption and greenhouse gas emissions in relation to freshwater biodiversity have so far
not been addressed in LCA context.
Global warming and increases in water consumption can significantly affect freshwater
ecosystems.13,14 For example, reduced river discharge (the volume of water flowing through a
river per unit time) due to water consumption and greenhouse gas emissions could lead to
freshwater fish species losses.15 In lotic freshwater ecosystems, river discharge can be used as
a surrogate of habitat space to generate species-discharge relationships similar to terrestrial
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species-area curves.15-17 Because climate warming and water consumption is expected to
reduce river discharge in many parts of the world,18 these species-discharge relationships have
been used to forecast species diversity losses associated with reductions in freshwater. In
addition, river discharge reduction can, for instance, lead to a higher concentration of
nutrients and pollutants in freshwater15 thus compounding the negative effects of water
quantity reductions alone on biodiversity. Changes in temperature and precipitation associated
with global warming can also adversely affect water availability. It is expected that river
discharge reduction due to global warming can negatively influence the distribution and
occurrence of many fish species (Figure
1
).7,19,20
The aim of this paper is to derive characterization factors related to freshwater ecosystem
damage for water consumption and greenhouse gas emissions. The present study focuses on
the occurrence of freshwater native fish species in global rivers. In order to put our results into
LCA perspective, we also calculate normalization factors for water consumption and global
warming as input for overall normalization factors that represent biodiversity impacts in
freshwater. Normalization factors provide information about the relative importance of each
impact category considered, such as impacts on freshwater biodiversity. .
Methods
Fram ework. Figure 1 gives an overview of the cause-effect chain regarding the
disappearance of freshwater fish species caused by greenhouse gas emissions and water
consumption. In this study, water consumption refers to water used for human activities, (e.g.
communal, agricultural and industrial) that is not returned to the river. The influence of
reduced flow rates on fish species numbers can be quantified with the global species-
discharge model, an index of habitat space, feeding and reproductive opportunities. This
model was developed on the basis of information on native fish species and river discharges
in various river basins (Xenopoulos et al.).14 This model assumes a positive correlation
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between the number of freshwater fish species and average river discharges at the mouth of
river basins.
R = 4 2 • QHLh (1)
where R is the freshwater fish species richness and Qmouth is the annual average river discharge
at the river mouth of basin i (m3.s-1).
The species-discharge relationship can be used as a basis to calculate characterization
factors for water consumption that specify freshwater fish species extinction per unit of
reduced river discharge for river basins in different regions of the world.14 This has been done
in a river basin-specific way. Using the data provided in Xenopoulos et al.,14 information of
the average river discharge for 326 river basins was considered. These 326 rivers include
well-known river basins in the world, representing a wide geographical distribution of rivers
around the various continents. However, we excluded 83 river basins which are located at
latitudes higher than 42o, because these river basins were recently (in geological time)
glaciated, i.e. covered by ice. As such, these rivers have not had enough time to evolve to
their maximum species richness potential. It follows that the species-discharge relationship
for these river basins is weak as they have much fewer species per unit discharge than the
rivers below 42o. This indicates that most of the world’s river basins located in the high
latitudes including Northern Europe, Northern America and Canada were not taken into
account. In addition, due to data limitations in the river volume and length calculations, 29
river basins were also excluded. Thus, a total of 214 river basins were used in our final
models.
The species-discharge relationship can also be used to derive characterization factors that
quantify the potential extinction of freshwater fish species per unit of greenhouse gas
emission. The endpoint modelling for global warming further includes the influence of
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