Ecosystems

Impacts on Terrestrial and Freshwater Biodiversity: Habitats and Ecosystems

Australia wide

• Woody thickening - an increase in the density of trees and shrubs at the expense of grassland species - is occurring across all major Australian ecosystems
• For some terrestrial species, increased woody vegetation may provide more habitat, but other species that rely on open habitats could be threatened or outcompeted by encroaching shrubs and trees¹⁰⁸

• Thickening is predicted to be a major issue as climatic changes progress ¹⁰⁹
• Some species will be directly threatened by woody thickening - the endangered golden shouldered parrot, endemic to Cape York Peninsula, is threatened by increased predation risk and impacts of thickening on seasonal food availability¹¹⁰
• Prescribed burning can stall thickening but timing of the burn is vitally important - in the north, burning in the late dry season and storm-season favours the maintenance of grassland, while burning at other times favours the woody species ¹¹¹

Mediterranean woodland and shrublands

• Lower annual rainfall and increased abstraction have lowered groundwater levels and negatively affected native vegetation ¹¹²
• Tree mortality and progressive floristic change towards drought tolerant species in Banksia woodlands^{113,114, 115,116}
• Lower rainfall and seasonal shifts in intensity have resulted in declines in streamflow, soil water storage and groundwater levels, affecting flora^117,118

•  Projected  declines in rainfall,¹¹⁹ streamflow¹²⁰ and groundwater levels ¹²¹ resulting in ecosystem stress and changes in community composition^{122,115, 123}
• Projected  temperature increases and rainfall declines may negatively affect South West Australian Floristic Region’s endemic plant diversity^124,125,126
• Suitable habitat will decline for many endemic Banksia species ^125,126
• Community composition changes as susceptible species decline in Western Australia¹²⁵

Temperate forests, woodlands and grasslands (including montane and rainforest)

• Increase of mire wetland  associated with contraction of eucalypt woodland in south-east Australia¹²⁷

• Production could increase where rain is not limiting, due to increased CO₂^128,129
• Reduced forest cover associated with soil drying¹²⁸
• Generally earlier grass¹³⁰and tree flowering¹³¹
• Conversion of grassland to woodland or shrubland
• Loss of carbon stocks through changed fire regimes and drying^{132,133,134,135}

Tropical savanna and grasslands

• Plant mortality following drought^136,137
• Expansion of rainforest at expense of eucalypt savanna and grassland in Northern Territory and Queensland associated with increased rainfall and CO₂^138,139
• Increasing canopy cover in tropical savannas¹⁴⁰

• Shift in composition could occur from perennial Mitchell grasses to annual grasses or forbs¹⁴¹
• Shift from C3 to C4 plants¹⁴²

Tropical and sub-tropical rainforest

• No reported impacts at time of press.

• Increasing floristic turnover for species at the altitude of the cloud base¹⁴³
• Changes to structure of rainforest canopy¹⁴⁴
• Damage to shallow-rooted species from high-intensity cyclones^{145 -} and subsequent potential for weed invasion¹⁴⁶
• Increased growth of vines with increased CO₂, leading to tree mortality¹⁴⁷
• Drying of tropical montane cloud forest, reducing productivity¹⁴⁸
• Rainforest contraction with increased fire frequency, favouring fire-tolerant species¹⁴⁹
• Short term heat events and drought likely to affect cool rainforest species more than dry rainforest species¹⁵⁰

Arid and semi-arid   regions

• Vegetation thickening in semi-arid mulga woodlands in southwest Queensland¹⁵¹  

• Altered competition between C3 and C4 grasses, favouring C4 species¹⁴²
• Relatively flat landscape may mean community change will be widespread and more extensive than in other regions, as there is little opportunity for altitudinal shifts¹⁵²  
• Reduction in patches of fire-sensitive mulga in spinifex grassland could lead to increase in spinifex¹⁵³

Alpine regions

• Decline in depth and duration of snow cover¹⁵⁴
• Tree line shifts of 30-40 m in altitude in 25 years in Victoria¹⁵⁵
• Increase in shrub cover and decrease in grass cover particularly in response to drought ¹⁵⁶

• Decline in specialist alpine ecosystems e.g. snow patch herb fields, cushion plants ¹⁵⁷
• Contraction of fens and bogs¹⁵⁸
• Native and feral mammals projected to move to higher elevations¹⁵⁹
• Encroachment of snow gums into subalpine grassland and higher elevations¹⁵⁵
• Frost damage in snow gums due to interaction between warming and increased CO₂ ¹⁶⁰
• Generally earlier time of flowering, seed set and budding with associated fitness effects^161,162

Inland wetlands and waterways (including peatlands)

• General reductions in flow and changed seasonality of flow, causing drying^163,164
• Contraction of Melaleuca swamp forests in Kakadu due to intrusion of salt water¹⁶⁵
• Drought-related mortality in floodplain forests¹⁶⁶

• Degradation and drying of peatlands¹²⁷; drying of wetlands; loss of seasonal ponds¹²⁷
• Drought conditions likely to become more common in Murray-Darling Basin, south-east and south-west Western Australia¹⁶³
• More frequent burning of peaty sediments in wetlands¹⁶⁷
• Loss of taxa intolerant of temperature rises¹⁶⁸
• Shifts to species-poor, salt-tolerant biota in southern wetlands with drying    climate ¹⁶⁴

Islands (including Heard, McDonald, Macquarie, Frasier, Christmas, Torres Straits; Lowe Howe and Norfolk Island groups)

• Change in mossy cloud layer may lead to reduced occult precipitation which affects the ability of vegetation to harvest moisture¹⁰⁹
• Changes in vegetation cover and loss of endemic flora and fauna
• Erosion of dunes, coastal cliffs and rocky shore platforms
• Changed fire regimes
• Deglaciation; establishment of introduced species in ice-free ground ¹⁷⁰
• Fundamental changes in the condition of subantarctic lakes and ponds¹⁰⁹

Coastal (estuarine, sandy, rocky)

• Increase in mangrove extent (1974-2004) in Northern Territory, likely due to rising sea levels and increased CO₂¹⁷¹
• Landward mangrove  expansion linked to increased rainfall in the south east¹⁷²
• Change to structure and composition in Tasmanian saltmarsh community¹⁷³

• Marine inundation of terrestrial systems with sea level rise¹⁷⁴
• Rocky shore and saltmarsh species vulnerable to total loss of habitat¹⁷⁵
• Saltmarsh and wetlands affected by landward movement of mangroves¹³⁸
• Coastal squeeze - coastal habitats trapped between landward boundaries and rising sea level¹⁷⁶