The Gunbower Forest is located in Northern Victoria, Australia. It hosts wetlands that are deemed of international significance under the Ramsar Convention. However, the site has been influenced by human use such as aboriginal occupation, climate change, river regulation, nutrient enrichment and sedimentation.
Sediments constitute natural archives of past environmental changes. Recovering and analysing this evidence using palaeoecological approaches provide a powerful insight into how these wetlands have responded to changes in human occupation and other factors, such as climate. Therefore, sediment cores were extracted from four wetlands selected to compare the impact of land use: Black (84cm) and Green (86cm) Swamps located in the forest, and Taylors (94cm) and Cockatoo (74cm) Lagoons situated amongst dairy farms.
These cores were analysed using four different techniques i.e. Itrax scanning, 210Pb dating, stable isotope and diatom analysis. Itrax (XRF) scanning provided information about the elemental composition of the cores. Stable isotopes revealed evidence on the carbon and nitrogen sources. The 210Pb analysis showed sedimentation rates to be 1cm/yr in Taylors and Cockatoo Lagoons whereas Green and Black Swamps showed 0.6cm/yr and 0.8cm/yr respectively. This is comparable to other sites analysed across the Murray Darling Basin.
The diatom records of the forest sites revealed a shift from clear water benthic species to an assemblage dominated by river plankton. A similar change was evident in the dairy sites, however recent increases in eutraphentic diatom species suggested additional, local sources of nutrients.
This comparative study suggests that there have been changes in the condition of wetlands in both forest and dairy country, so the main driver of change is likely to be regional, possibly via the influence of the distributary Gunbower Creek. The intensive dairy activities appear to represent an additional stressor on nearby wetlands. As the main changes are recent it suggests that the condition of the wetlands is continuing to degrade.