An International Union for the Conservation of Nature Red List ecosystems risk assessment for alpine snow patch herbfields, South-Eastern Australia

Abstract

Alpine ecosystems are globally at risk from climate change. We use the International Union for the Conservation of Nature (IUCN) Red List Criteria for ecosystems to assess the risk of ecosystem collapse in Australian alpine snow patch herbfields. These ecosystems occur on both mainland Australia and Tasmania. They are restricted to steep, south-easterly slopes where snow pack persists well into the summer growing season. Consequently, they are rare, and have high conservation significance.We evaluated the risk of snow patch herbfield ‘ecosystem collapse’ against criteria that accounted for the ecosystem’s restricted distribution, projected decline in the snowpack and increased rates of invasion by taller growing native species of shrub and grass. Our analyses revealed considerable uncertainty in estimates of risk based on some criteria, particularly those related to thresholds of ecosystem collapse caused by biotic change. On the basis of the IUCN Red List criteria, we conclude that the ecosystem is ‘endangered’.This is because of the restricted geographical distribution of the ecosystem, a substantial and highly likely decline in the abundance of snow (the principal abiotic driver of the ecosystem), and the prospect of invasion of much of the ecosystem by taller growing native shrubs and grasses. Our case study demonstrates the utility of the Red List methodology for assessing risks to biodiversity in rare ecosystems where changes to both abiotic factors and the relative dominance of native species constitute major threats. Our findings indicate the importance of snow patch herbfields as refugia for dwarf alpine plant species in the face of climate change, the need for continued monitoring, the removal of feral animals from the Australian Alps and scenario planning.