Poor correlation between large-scale environmental flow violations and
freshwater biodiversity: implications for water resource management and
water planetary boundary
Abstract
The freshwater ecosystems around the world are degrading, such that
maintaining environmental flow (EF) in river networks is critical to
their preservation. The relationship between streamflow alterations and,
respectively, EF violations, and freshwater biodiversity is well
established at the scale of stream reaches or small basins
(~<100 km²). However, it is unclear if this
relationship is robust at larger scales even though there are
large-scale initiatives to legalize the EF requirement. Moreover, EFs
have been used in assessing a planetary boundary for freshwater.
Therefore, this study intends to carry out an exploratory evaluation of
the relationship between EF violation and freshwater biodiversity at
globally aggregated scales and for freshwater ecoregions. Four EF
violation indices (severity, frequency, the probability to shift to
violated state, and probability to stay violated) and seven independent
freshwater biodiversity indicators (calculated from observed biota data)
were used for correlation analysis. No statistically significant
negative relationship between EF violation and freshwater biodiversity
was found at global or ecoregion scales. While our results thus suggest
that streamflow and EF may not be an only determinant of freshwater
biodiversity at large scales, they do not preclude the existence of
relationships at smaller scales or with more holistic EF methods (e.g.,
including water temperature, water quality, intermittency, connectivity
etc.) or with other biodiversity data or metrics.