Morialta Conservation Park: Is the Biodiversity Hub Threatened by the European Olive?

Morialta Conservation Park is one of the most loved and most visited parks in the Greater Adelaide Area. Surprisingly, relatively few studies have been done in this park despite it being visited by so many people. A couple of years ago, Jacynta Anderson set out to change this by undertaking the first systematic survey of the vegetation in the park. She found that the park had extraordinary biodiversity but also that it is threatened species, particularly the European olive.

Besides being very scenic and relatively small in area, Morialta is home to 16% of South Australia’s flora – on less than 0.0001% of the state’s total area. The park also hosts most of the major vegetation formations known to occur in the Mount Lofty Ranges. Furthermore, a total of 17 species that are considered endangered on the state or federal level or on the IUCN Red List are found in the park. Therefore, Morialta punches well above its weight in providing protection for South Australia’s flora and ecosystems.

The scenic landscape, rugged topography and diversity of vegetation formations in Morialta Conservation Park. (Photo: Gunnar Keppel)

But how is Morialta Conservation Park able to sustain such a diversity of species and vegetation formations in such a tiny space? The answer relates to the geology and topography of the park. Since the formation of the Mount Lofty Ranges began some 470 million years ago, geological processes have created and exposed various substrates and created different soil types, producing a mosaic of different bedrocks and topographies. In short, Morialta Conservation Park encompasses an area of great habitat diversity, which in turn supports a variety of species and vegetation formations.

However, the more recent geography has been less favourable for the park’s biodiversity. Before being declared a conservation park in 1974, parts of the park had pastoral uses, were olive plantations or were supplemented with introduced species for aesthetic purposes. The park also borders suburban Adelaide. As a result, the park has a plethora of species not native to the area, with Jacynta’s study recording 300 introduced plant taxa inside, or within 1 km, of the park.

While most of these 300 species are not currently a problem, the European olive, Olea europea, certainly is. In South Australia, feral olives (that is, olives growing ‘wild’ outside of plantations) are declared weeds. Jacynta’s study not only found olives growing in 15% of her sample plots, but also sampled three locations that were dominated by dense stands of olives. This highlights the need to 1) manage the further spread of olives in the park, and to 2) identify existing olive stands and to carefully replace these stands with native vegetation. Otherwise, native vegetation in the Morialta Conservation Park might be slowly replaced by dense stands of olives.

The detailed study can be found here (please contact the author of this blog for a pdf of the article):

Anderson, J., Keppel, G., Thomson, S.M., Gibbs, J., and Brunetti, G. (2020) High diversity of native plants and vegetation types in the Morialta Conservation Park and the threat of invasive species. Transactions of the Royal Society of South Australia, doi: https://doi.org/10.1080/03721426.2020.1786779

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