Assessment of
Australia’s Terrestrial Biodiversity
2008

Chapter 5 Threats to Australian biodiversity

These pages have been extracted from the full document which is available at: http://www.environment.gov.au/biodiversity/publications/terrestrial-assessment/index.html

© Commonwealth of Australia 2009

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The then National Land and Water Resources Audit’s Biodiversity Working Group had a major role in providing information and oversighting the preparation of this report. The views it contains are not necessarily those of the Commonwealth or of state and territory governments. The Commonwealth does not accept responsibility in respect of any information or advice given in relation to or as a consequence of anything contained herein.

Cover photographs:
Perth sunset, aquatic ecologists Bendora Reservoir ACT, kangaroo paw: Andrew Tatnell.
Ecologist at New Well SA: Mike Jensen

Editor: Biotext Pty Ltd and Department of the Environment, Water, Heritage and the Arts

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Chapter5
Threats to Australian biodiversity


The threats to Australia’s plants, animals and ecological systems are numerous and wide ranging. The Australian landscape shows the legacy of past threats that are still actively impacting on our biodiversity. New and emerging threats, particularly climate change and water scarcity, are intensifying and will persist well into the future.

It is important to keep in mind that the direct drivers of biodiversity loss result from a complex of interacting economic, socio-political, and scientific factors, which influence human activities (Secretariat of the Convention of Biodiversity 2006).

Efforts to address some key threats have been scaled up. In particular, broad-scale land clearing has been largely brought under control in the jurisdictions that accounted for most of the clearing in 2002: New regulatory frameworks in Queensland and New South Wales have dramatically reduced the level of approved clearing of remnant vegetation nationally in the past five years.

Reforms to water management through recent Council of Australian Governments (COAG) initiatives have the potential to address another key threat: altered hydrology. The new reforms include mandatory consideration of environmental (aquatic ecosystem) requirements for water in all new water allocation and planning.

The significance of climate change as a threat to biodiversity has become much more widely recognised since 2002; climate change now ranks as an important threat to Australian biodiversity overall. Knowledge of climate change scenarios and impacts is rapidly growing as Australian scientists and science institutions increase efforts to understand this threat.

The key findings from the Assessment of Australia’s Terrestrial Biodiversity 2008 (hereafter referred to as the ‘Assessment’) are listed below in section 5.1.

5.1 Key findings

Key threats are habitat fragmentation and the spread of invasive species. / A national analysis of the documentation and recovery plans for threatened species and communities listed under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) found that the most frequently cited threats are those of habitat fragmentation and the spread of invasive species
Weeds remain a threat to biodiversity but their impacts on biodiversity are not generally assessed. / Weed management strategies and policies have historically failed to address impacts on biodiversity adequately.
There are already a number of observed impacts from changes in the climate. / Observations of changes in native species and natural systems linked to climate change in Australia include: the expansion of rainforest at the expense of savanna; the encroachment by snow gums into sub-alpine grasslands at higher elevations; saltwater intrusion into freshwater swamps; and changes in bird behaviour including arrival of migratory birds, range shifts and sea-surface temperature induced reproductive changes.
Selected case studies illustrate specific impacts of climate change. / A number of findings emerge from the selected case studies: impacts of threats are complex and variable; impacts are difficult to predict and generic modelling will require substantial localised input to be relevant; long-term monitoring is required.
Case studies of land use change show the threat posed to biodiversity by such change. / A high percentage of species are absent from cleared areas. Most species, however, can occur in regrowth (Queensland) or corridors of native vegetation (Northern Territory).
Understanding species’ requirements in terms of patch size and connectivity may allow the ‘design’ of landscapes with some clearing that retain vertebrate biodiversity.
Grazing pressure is a longstanding threat over much of the Australian landscape. / Almost 60 per cent of the Australian land mass is used for the production of livestock based on native pastures.
Strong linkages between artificial watering points and impacts on biodiversity can serve as an indicator of grazing pressure.
Information on monitoring fire distribution and frequency has improved greatly. / Fire frequency maps over the period 1997 to 2006 illustrate higher frequencies of fire in the central arid lands, northern savannas; a clear relationship with extended aridity; and frequent uncontrolled wildfires in southern Western Australia, south-east Victoria and coastal southern New South Wales.
Our knowledge of biodiversity responses to fire is still patchy. / Altered fire regimes affect biodiversity and interact with other threats in complex ways that are not yet fully understood.

5.2 Indicators

Indicators reported in this chapter are listed in Table 5.1.

Table 5.1 Indicators

Indicator / Current reporting capacity rating
Trends in habitat fragmentation and decline in ecosystem function / Poor nationally
Moderate at case-study level
The range and relative importance of threats to biodiversity over time / Poor nationally
Moderate for listed species and communities
·  Trends in the impacts of climate change on biodiversity / Poor nationally
Poor at case-study level
Trends in the impacts of land use change on biodiversity
·  Trends in land clearing rates / Poor nationally
Good for clearing rates in Queensland
Moderate at case-study level
Trends in the impacts of invasive species and pathogens on biodiversity
·  Extent and distribution of important invasive species / Poor nationally
Good at case-study level
·  Trends in the impacts of grazing pressure on biodiversity / Poor nationally
Moderate at case-study level
·  Trends in the impacts of altered fire regimes on biodiversity / Poor nationally
Good at case-study level

5.3 The range and relative importance of threats to biodiversity

The key threats to biodiversity are:

·  fragmentation

·  climate change

·  land use change

·  invasive species and pathogens

·  grazing pressure

·  altered fire regimes, and

·  changed hydrology.

These interacting threats vary in their impacts across the country and over time. A national analysis of the documentation and recovery plans for threatened species and ecological communities listed under the EPBC Act found that the most frequently cited threats are those of habitat fragmentation and the spread of invasive species (Figure 5.1).

The nominations of threats for EPBC listings have changed. Before 2002, climate change was rarely noted, but more recently it is identified as a threat for every new listed species and ecological community.

Figure 5.1 Habitat fragmentation and invasive species pressure on EPBC listed species and communities

5.4 The impacts of climate change on biodiversity

Evidence that climate change is causing global and regional warming is unequivocal (Intergovernmental Panel on Climate Change 2007). Regional warming has been associated with changes in physical and biological systems in many parts of the globe. Australia has warmed by 0.9˚C since 1900 and is expected to warm a further 1˚C over the next two decades (Olsen 2007).

There is significant uncertainty regarding how species and ecological systems will be impacted by climate change. Current regional climate models suggest that impacts will be widespread and that a ‘business as usual’ scenario over the next few decades will result in global mass extinctions on a scale previously unseen in human history (IPCC Working Group II 2007). There is mounting evidence that, even with concerted mitigation effort, it may not be possible to avoid impacts of climate change such as the loss of large components of biodiversity including freshwater systems, coral reefs and coastal mangroves (Steffen 2008). The north Australian wetlands and the Great Barrier Reef are among these threatened assets.

Recent studies show that impacts in Australia will be complex and highly variable (CSIRO and Australian Bureau of Meteorology 2007a; Figure 5.2). The distribution, diversity and abundance of species and the functioning and dynamics of ecosystems will change, with some responding better than others. The most vulnerable species include those with very restricted geographic and climatic range, those unlikely to migrate successfully and/or those already highly compromised by small populations, fragmented habitat and other threats. These include some of Australia’s most threatened and iconic species (World Wildlife Fund 2008).

The threat of climate change include the direct impacts on habitat, ecosystem functioning and populations of higher concentrations of carbon dioxide; altered rainfall and temperature patterns; rising sea levels; increased sea temperatures and acidity; and more frequent extreme storms, floods and heatwaves. Many species are highly sensitive to changes in climate and weather-related patterns and events. These can disrupt seasonal food supplies and other resources, life cycle events, development, mortality, breeding and fertility, such that entire reproductive strategies become less successful. Expected direct impacts on species populations include:

·  changes in species abundance

·  changes in distribution, and

·  changes in genetics over the long term as species adapt.

Climate change will compound other threats to biodiversity, including changed hydrology, fire and invasive species. Warmer, drier conditions in southern Australia, in particular, are predicted to lead to more frequent severe drought and wildfires. The changing climate is also likely to favour invasive species in many areas and reduce the competitiveness of Australian flora and fauna in their existing ranges. Migration of native species into new and locally more favourable areas will also have implications for extant populations.

Figure 5.2 Trends in temperature and rainfall

The ability of species to adapt to changing conditions and recover after extreme climatic events will be compromised by the legacy of fragmentation, habitat loss and other pressures that have collectively reduced overall diversity, population sizes and resilience in many species.

Less direct threats include the impacts of development shifts in response to changing water availability. The north of Australia includes vast areas of relatively intact native forest, woodlands and grasslands, and regions of rich biodiversity that may be at risk from future development and changing land uses.

5.4.1 Observed impacts on natural systems and biota

The recent Intergovernmental Panel on Climate Change Working Group II assessment collated available evidence and observations of changes in native species and natural systems linked to climate change in Australia (Hennessy et al 2007) including: expansion of rainforest at the expense of savanna (Bowman et al 2001, Hughes 2003); encroachment by snow gums into sub-alpine grasslands at higher elevations (Wearne and Morgan 2001); increased movement of feral mammals into alpine areas and prolonged winter presence of macropods (Green and Pickering 2002); saltwater intrusion into freshwater swamps possibly associated with sea level rise (Winn et al 2006); changes in bird behaviour including in arrival of migratory birds, range shifts and sea-surface temperature induced reproductive changes (Smithers et al 2003, Chambers 2005, Chambers et al 2005, Beaumont et al 2006); change in genetic constitution of Drosophila equivalent to a 4° latitude shift (Umina et al 2005).

5.4.2 Case studies of the impacts of climate change on biodiversity

Although many studies are in progress and numerous lines of evidence and observations are emerging in relation to climate change impacts on biodiversity (Dunlop and Brown 2008, WWF 2008), many uncertainties remain, and it is not yet possible to provide a national picture. While there is no single indicator of the impact of climate change a number of indicators already used in this Assessment can serve, e.g. trends in the condition of native vegetation, and trends in the extent and distribution of threatened species and communities. This is consistent with the approach taken internationally (Secretariat of the Convention of Biodiversity, 2006). Trends in the extent and distribution of wetlands may also be considered.

This Assessment commissioned a range of case studies to investigate specific impacts of climate change in particularly vulnerable areas, and to illustrate some of the new methodologies being developed to help us understand how climate change is likely to impact on ecosystems, habitat, species and populations over time (Table 5.2).

Table 5.2 Case studies of climate change impacts on biodiversity

Case study / Jurisdiction/agency
Will climate change affect Australian birds? / National
Impacts of climate change on the biodiversity of the Victorian Alps / Victoria
Sea level rise and biodiversity in the Coorong / South Australia
Predicting climate change impacts on World Heritage rainforests in south-east Queensland / Queensland
Monitoring the impact of climate change on biodiversity in Tasmania / Tasmania
Community-level modelling of climate change impacts on biodiversity in New South Wales / NSW
Climate change and soil biodiversity / CSIRO

The following findings from the seven selected case studies provide early signals about the probable effects of climate change on biodiversity:

·  Impacts of climate change on biodiversity will be complex and highly variable. For example, changing phenology can change the competitive advantages of species within a community and thus community composition.

·  The impacts of climate change on biodiversity will be very difficult to predict, and generic models will require substantial localised input in order to be relevant.

·  Monitoring of biotic responses is critical to understanding the direction and speed of the changes.

·  Most current research deals with the direct impacts of climate conditions on plants and animals. Very little research examines the more complex ecological interactions likely to result from climate change.

·  Responses to other variables, including CO2 concentrations, and the interactions with other key threats are still unclear.

·  The resilience of natural systems, species and populations to climate change is largely unknown. Many taxa are already compromised by the ongoing effects of other threats and are therefore highly vulnerable to shifts in climate-related conditions.