Climate Change: Defining Reference Conditions and Restoring Freshwater Ecosystems - Climate Change Impacts on Freshwater Ecosystems - page 206

Fish abundance
Fish age structure
Fish sensitive taxa
Invertebrate abundance
Invertebrate sensitive taxa
Invertebrate diversity
Phytobenthos

Macrophyte

Phytoplankton abundance
Phytoplankton blooms

0 20 40 60 80 100

Fish abundance
Fish sensitive taxa
Fish age structure
Invertebrate abundance
Invertebrate sensitive taxa
Invertebrate diversity
Phytobenthos abundance
Macrophyte abundance
Phytoplankton abundance
Phytoplankton blooms

Spatial
Palaeoecology
Model
Historical
Expert

0 20 40 60 80 100

Percent

Figure 9.1 Frequency (%) of methods used by 12 European countries to establish
reference conditions. (Data are taken from the REFCOND, http://www-nrciws.slu.se/
REFCOND/doc_rew2.html.)

to define a more holistic reference condition that includes ecosystem-level
attributes. However, one caveat with expert judgement is that it often consists of
a narrative articulation of a perceived reference condition, and consequently this
approach may introduce subjectivity (e.g. the common perception that it was
always better in the past) and bias (e.g. experts may disregard sites having naturally
low diversity) and can be extremely inaccurate. Another weakness is that the
measure obtained is often static and therefore neglects the dynamic and inherent
variability often associated with natural ecosystems. Consequently, expert
judgement is seldom used as a single method to establish reference conditions,
but may be a strong complement when combined with other methods.
Methods used to establish reference conditions of European inland surface
waters were reviewed by the EU-funded project REFCOND (Development of a
protocol for identification of reference conditions, and boundaries between high,
good and moderate status in lakes and watercourses) (Wallin et al . 2003).
Approaches were found to vary between lakes and watercourses and with
biological quality elements (Fig. 9.1). Spatial approaches were the most common
methods used by the 12 countries that participated in the survey (mean = 31%