The Yalgorup Lake System is home to the largest natural stand of Tuart (E. gomphocephala) in the world. E gomphocephala is a woodland tree endemic to the Swan Coastal Plain of Western Australia. It is of supreme importance in this area as it is one of the few eucalypts capable of surviving on limestone soils (Barber et al., 2010).
What is certain is that the tuarts in and around Yalgorup need help and not more
stress from interference with ground water, under storey clearing and all the
other impacts that would come with a significant population increase in the area.
When the Europeans arrived on the shores of Western Australia Tuart woodlands covered the coastline. As the population increased the trees were removed to make way for houses. Now the only significant stand of Tuarts is to be found in and around the Yalgorup National Park.
Tuarts are an integral part of the ecosystem of the Western Australian coastline. They sequester carbon, release oxygen, filter out the nutrients from the ground and give top storey cover to the abundant biodiversity of the southwest.
The tuarts are supported by the Superficial aquifer lying in a shallow layer over the porous Tamala limestone beneath the surface. The quantity and quality of the water in this aquifer is critical to the health and wellbeing of the Tuarts and the ecosystem of the Yalgorup Lakes.
Should the quantity of the water or the level of the fresh groundwater lens below the surface be reduced, the tuarts will be put under stress. When the trees are under stress they are susceptible to disease and die back as occurred in 1997 around Preston Beach with mortality as high as 90%.
Maintaining the level of the groundwater in the Superficial aquifer is therefore essential to the sustainability of the tuart population. With the reduction in the rainfall in the southwest since 1970 this is a challenge. Strictly limiting the removal of water from this aquifer is therefore essential both to maintain the tuarts and the integrity of the Yalgorup Lake Ecosystem (Peel Coastal groundwater allocation plan, 2014).
For more information go to Western Australian Centre of Excellence for Climate Change, Woodland and Forest Health