K'gari (Fraser Island) World Heritage Area: evaluating change in plant species richness and composition over two decades.

Context: K'gari (Fraser Island) World Heritage Area in eastern Queensland is the largest sand island in the world and is characterised by a diversity of landscapes, ecosystem types and cultural values. The biodiversity values are threatened by degradation associated with increasing visitor numbers, inappropriate fire regimes, invasive plants and animals, and climate change. Aim: This study investigated changes in vegetation community attributes (species richness and composition) monitored for over two decades. Methods: Twenty-two long-term vegetation monitoring sites established in 1995 were resurveyed in 2021 and analysed. Key results: The sites experienced between one to five fire events in the period from 1994 to 2020. Species richness and the overall differences within regional ecosystems through time were not statistically significant at P ≤ 0.05. A comparison between observed species in the 2021 survey against a list of expected species within each regional ecosystem showed no statistically significant difference (t 7 = 0.649, P = 0.268). Recently burnt sites showed the greatest degree of dissimilarity. Six invasive plant species that are known environmental weeds were recorded. Conclusion: Our research suggests that most vegetation communities in K'gari are adversely affected by widespread, severe bushfire but are resilient; except for Casuarina equisetifolia subsp. incana communities on exposed frontal areas and dry peat swamps. Implications: Targeted planned burning is a key management tool that aims to achieve fire regimes appropriate to the ecosystems and to mitigate risk of severe bushfires. Hence, timely implementation of the existing planned burn guidelines for the south-east Queensland Bioregion is imperative. The K'gari (Fraser Island) World Heritage Area in Queensland faces threats from visitor impact, fire practices, invasive species, and climate change. A two-decade study examined vegetation changes at 22 monitoring sites. Although fire events occurred, there were no significant differences in species richness or composition over time. Recently burned sites showed higher dissimilarity. Six invasive plant species were identified. Timely implementation of existing planned burn guidelines is crucial for mitigating risks and preserving the K'gari vegetation communities. [ABSTRACT FROM AUTHOR]