Natural Temperate Grassland of the South Eastern Highlands

Status: Critically Endangered on the EPBC Act list

This ecological community is a natural temperate grassland, typically dominated by perennial tussock grasses, and predominantly occurring on plains of the south eastern highlands. It occurs at altitudes up to approximately 1200 m in and around the South Eastern Highlands.

Government evidence of impact of climate change:

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  • Approved Conservation Advice (including listing advice) for the Natural Temperate Grassland of the South Eastern Highlands (EC 152)

    Climate change Key threatening processes.

    The identified factors are influences associated with Holocene glacials; that is; the previously colder and drier conditions that prevailed in the region deep; mineral; relatively fertile soils basaltic and alluvial soils; regardless of climatic conditions heavy clay soils that crack in summer; causing death of newly established tree seedlings competitive exclusion of woody vegetation by grass roots and sward allelopathy (subtle chemical effects that kill or stunt growth of seedlings of woody species) attraction of grazing animals to grasslands; which in turn destroy seedlings of woody plants severe frosts (particularly low probability; low temperature events and radiation frosts) severe frosts are lethal to seedlings of woodland and forest tree species fires (particularly in combination with grazing); which suppresses tree and shrub recruitment the pre settlement patterns of burning by Aboriginal people and; periodic water logging; especially in low lying areas in association with frost.

    Prolonged droughts; like the one that was experienced throughout the first decade of the 21st century; and possibly climate change; are likely also to contribute to the formation of grassland evidence for this is the widespread mortality of woodland trees across the Monaro in recent years (Rehwinkel; pers. comm.).

    Climate change By 2050; the region in which the ecological community occurs is predicted to experience a general warming in all seasons; reduced winter and spring rainfall; and increased summer rainfall (DECCW; 2010a Dunlop et al.; 2012 Lavorel et al.; 2015).

    It is predicted that climate change will exacerbate existing threats and put increasing pressure on the ecological community as a whole.

    There are also expected to be severe changes to the community s structure; composition and resultant ecological functioning due to the effects of human induced climate change.

    Changes to the structure and floristics of NTG SEH due to climate change are likely to occur; through changes to a dominance of summer growing or C4 grasses; depletion of native groundlayer vegetation; increased invasion of weed species; loss or depletion of moisture dependent associations of the ecological community; and higher grazing pressures from increases in populations of herbivores (DECCW; 2010a Dunlop et al.; 2012 also see Appendix D).

    In particular; the response of the ecological community; component species and weeds to alternative fire and grazing regimes; including intensity and seasonality (timing) and other role of these disturbances in maintaining the ecological community.

    The resilience of grassy ecosystems to fire is likely to have changed because of floristic compositional changes resulting from other disturbances; or from the long term exclusion of fire.

    Too frequent burning or fires that are too hot or wrongly timed are identified as a threat to native grasslands; and particularly to the small; relatively immobile fauna species that occur in small; fragmented sites and to sensitive flora species (Environment ACT; 2005 SEWPAC; 2012a Dunlop et al.; 2012).

    These changes are likely to result in issues such as loss of resilience to degradation and fragmentation structural and compositional changes of the herbaceous ground layer o Changed C3 C4 ratios e.g. summer growing or C4 grasses; such as kangaroo grass; redgrass or the weed African lovegrass (Eragrostis curvula); are likely to replace the winter growing or year long green or C3 grasses; such as speargrasses and wallaby grasses. o Replacement of perennial grasses with annual species. o The loss or depletion of the moisture dependent associations; such as those found on the frost hollows and the beds of the large ephemeral wetlands; is also predicted. o Reduced pasture productions and increasing grazing pressure from from livestock; eastern grey kangaroos and other macropods and exotic herbivores. predominance of exotic plant species and reduced native forb diversity altered fire frequency; increased intensity and spread high rainfall areas under increased pressure for cropping and; cascading changes in ecological interactions.

    The processes of clearing; grazing by domestic stock and rabbits and changed fire regimes; along with the effects of fragmentation; species introductions; species depletions and extinctions; changes to soil properties and other forms of degradation have caused substantial changes to the natural structure and diversity of NTG SEH.

    The interaction of the above listed human induced impacts; superimposed upon the effects of the recent decade long drought has resulted in complex change within NTG SEH.