Journal
MARINE AND FRESHWATER RESEARCH
Volume 66, Issue 11, Pages 957-969Publisher
CSIRO PUBLISHING
DOI: 10.1071/MF14067
Keywords
ecosystem resilience; environmental condition; environmental flow; freshwater; historical data; meta-analysis; monitoring; population dynamics; state-space model
Funding
- CSIRO Water for a Healthy Country National Research Flagship
- Murray-Darling Basin Authority as part of the CSIRO Multiple Benefits of the Basin Plan Project
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The case for restoring water to the environment in the Murray-Darling Basin, Australia, is based mainly on condition assessments, although time series provide valuable information on trends. We assessed trends of 301 ecological time series (mean 23 years, range 1905-2013) in two categories: (1) population' (abundance, biomass, extent) and (2) non-population' (condition, occurrence, composition). We analysed trends using log-linear regression, accounting for observation error only, and a state-space model that accounts for observation error and environmental noise'. Of the log-linear series (n=239), 50 (22%) showed statistically significant decline, but 180 (78%) showed no trend. For state-space series (n=197) one increased, but others were stable. Distribution of median exponential rates of increase (r) indicated a small but statistically significant declining trend, though 35-39% of the series were positive. Our analysis only partly supports, though does not refute, prevailing assumptions of recent ecological decline in the Murray-Darling Basin. The pattern is of fluctuating stability, with declines during droughts and recovery after flood. The overall trend from our meta-analysis is consistent with a pattern of historical decline to a hybrid ecosystem followed by slow, recent decline for some components and stability for others, with considerable variation in trends of specific ecological components: in short, there are ecological winners' and losers'.
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