Assessing the relative impacts of land‐use change and river regulation on Burdekin River (Australia) floodplain wetlands

Abstract

The Burdekin River floodplain wetlands are internationally important and act as a sink for sediments and nutrients that would otherwise enter the World Heritage‐listed Great Barrier Reef lagoon. The Burdekin River has the highest natural discharge of any Great Barrier Reef catchment and contributes the greatest mass of sediment to the reef. The river and its catchment have been substantially modified by land clearance, river regulation introduced in the 1960s, the construction of the Burdekin Falls Dam in 1987 and invasive aquatic plants. We hypothesised that the natural variability of Burdekin River discharge would render its wetland ecosystems resistant to human‐induced pressures. Diatoms were analysed from the sediments of two lower Burdekin River floodplain wetlands with contrasting regulation histories. Labatt Lagoon has a long history of flow alteration, whereas Swan's Lagoon has experienced limited regulation. Both wetlands experienced dramatic increases in sedimentation as a result of land clearance, yet the Swan's Lagoon diatom record indicates that the wetland's ecology remains within the range of natural variability. In contrast, Labatt Lagoon is markedly different from its pre‐settlement state. It is now permanent, having been ephemeral for more than 1000 years before European settlement. The conversion to artificial permanence facilitated aquatic plant invasion, resulting in more marked changes than widespread pastoralism. Modern diatom assemblages from 28 lower Burdekin River floodplain wetlands indicate that the contemporary flora of Swan's Lagoon is unusual. Most wetlands have similar assemblages to those in the Labatt Lagoon record in its present, altered state. It is possible, therefore, that the ecological shift registered in Labatt Lagoon is widespread. Diatom records highlight the striking impact that river regulation has had on the trajectory of the Burdekin floodplain wetlands. It is likely that wetland rehabilitation can be facilitated by the re‐introduction of a variable hydrological regime.

Variations in wetland conditions within the Fitzroy Basin, north-eastern Australia: a palaeoecological approach

“…Both sites indicate changes in sedimentation patterns, with more sediment being deposited at Lake Mary North from the ,1700s CE and later at Tualka (,1900s CE). Increased sediment deposition post-European settlement has also been recorded in floodplain wetlands within the Burdekin Catchment, NACC (Tibby et al 2019).…”

“…Gell and Reid 2014;Gell et al 2016;Wingard et al 2017). Palaeoecological studies of NACC wetlands are limited; however, Tibby et al (2019) provided two palaeolimnological records from two tropical floodplain wetlands within the Burdekin Catchment, Queensland, Australia. Natural variability and wetland stressors were examined, with minor ecological change due to land clearing for grazing; however, hydrological modification caused a shift in diatom assemblage and increased invasive aquatic taxa.…”

Reynolds phytoplankton functional classification approach helps evaluate the historical ecological status of the large European Southern Bug River (Ukraine)

“…Reference conditions refer to undisturbed systems, but if they are not available, alternative approaches can be used: historical data, modelling of reference conditions, or, expert judgment (Mischke et al, 2018; WFD, 2000). Quantitative and qualitative approaches that could be used for setting reference (undisturbed) ecological conditions are analyzed based on long‐term data sets with a wide range of background scenarios (Bennion et al, 2004; Devlin et al, 2009; Tibby et al, 2019). Usually, the following metrics are applied: Q ( r ) quality index (Borics et al, 2007) based on the functional group (FG) classification of phytoplankton according to Reynolds et al (2002), saprobic index of algal community, dominant species, and the ratio between Pennales , Chlorococcales , and Cyanobacteria (Mischke et al, 2018).…”

Sedimentation from landscape clearance-induced soil erosion threatens waterhole persistence in a semi-arid river system, southern Queensland, Australia

“…In many parts of the state, this clearance escalated from the 1950s and still occurs at a high rate (Reside et al 2017), including in the Moonie River catchment (Queensland Government 2021). Despite the potential effects of land clearance on aquatic ecosystems in Queensland, there has been little investigation of its effects (however see Tibby et al (2019) for an example).…”