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freshwater from the hinterland was embargoed in order to preserve its perceived ecological
character. Salinity increased further during a drought in 2001-2009, leading to the replace-
ment of a complex system dominated by aquatic plants to a simple system dominated by
phytoplankton and brine shrimps. This regime shift was also associated with declines in fish
and migratory bird populations (Gell 2010, Dick et al. 2011). Analysis of diatoms and nitrogen
and carbon isotopes from sediment showed that the system had been naturally sub-saline
and tidal for most of its 7,000 year history and that the 1985 'baseline' salinity was far too high,
leaving the system vulnerable to the effects of drought and water extraction for agriculture
(Fluin et al. 2007, Krull et al. 2009). In this case, misunderstanding of the true baseline con-
tributed to ecological collapse (Gell et al. 2013). In another example, a catchment manager in
northwestern Victoria claimed that a shallow floodplain lake lying alongside the Murray
River was naturally saline, when in fact salinity had increased dramatically when irrigation
waters were diverted away from the lagoon, illustrating a case of misrepresentation of base-
line conditions in order to avoid liability for restoration (Gell 2010).
In contrast, salinity may also become too low relative to natural baselines, if wetlands
become 'polluted' with freshwater. Fossil diatom records shows that some coastal wetlands
and estuaries in the southeast of South Australia have been artificially freshened by water
from government drainage schemes further inland, aimed at creating pasture lands on sea-
sonal wetland areas (Haynes et al. 2007). Diatom records from Lake Alexandrina, for example,
show a high proportion of salt-tolerant taxa for most of the past 6,000 years, their abundance
only declining since the construction of barrages in the 1940s, which prevented saltwater
incursions and created conditions of artificially low salinity. This suggests that the proposed
environmental watering plan is misguided and costly, and anyway may become increasingly
difficult to achieve, given projected decreases in rainfall and runoff (Gell, 2010, Mac Nally
et al. 2011, Gell et al. 2012).
Wetland environments are variable and highly sensitive to environmental change, there-
fore baseline conditions need to be set carefully in the context of the long-term resilience and
variability of the ecosystem. The assumption that a wetland is in its natural state, or is at equi-
librium is likely to be unsafe in the Anthropocene, and wetlands are more likely to be in flux
than at equilibrium (Gell et al. 2013). Short-term perspectives can misleadingly skew environ-
mental goals, as illustrated by management issues that arose in the Peace-Athabasca Delta
(PAD), in northern Alberta, Canada (Wolfe et al. 2012). Covering over 6,000 km
2
, PAD is the
world's largest freshwater boreal delta, and comprises a productive landscape mosaic of shal-
low freshwater lakes, wetland and meadows. The delta is home to the world's largest herd of
bison and is an important oasis for migrating birds. Wood Buffalo National Park was created
in 1922, a UNESCO World Heritage Site, and a Ramsar Wetland of International Importance.
It is also highly culturally significant to the Mikisew Cree and Athabasca Chipewyan First
Nations and Métis (Wolfe et al 2007).
Unusually low levels in Lake Athabasca in the late 1960s coincided with the construction of
the Bennett Dam on the Peace River in British Columbia, leading to concern that reduced
frequency of ice-jam floods and floodplain water levels were threatening the replenishment of
perched basins that provide shoreline habitat for wildlife. Fears about future water availability
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