Land-use change, and habitat fragmentation and degradation threaten ecosystems and resilience

2016

Land clearing is a fundamental pressure on the environment. It causes the loss, fragmentation and degradation of native vegetation, and a variety of impacts on our soils (e.g. erosion and loss of nutrients), waterways and coastal regions (e.g. sedimentation and pollution).

The fragmentation and degradation of remnant vegetation can, in turn, disrupt essential ecosystem processes such as pollination, seed dispersal and regeneration. Smaller fragments of remnant vegetation are also vulnerable to invasive species and fire. Half of Australia’s species currently listed as threatened under the EPBC Act are considered to be at risk from habitat fragmentation. Habitat loss and fragmentation are identified as major threats that are responsible for the extinction of 11 Australian mammal species, and place significant pressure on a further 19 threatened species and 15 near-threatened species according to The action plan for Australian mammals 2012 (Woinarski et al. 2014a).

Pressure on the environment from land clearing, and habitat fragmentation and degradation includes a legacy of extensive historical clearing, which presents a considerable challenge for land managers because redressing historical impacts can be costly and difficult. Approximately 44 per cent of Australia’s forests and woodlands have been cleared since European settlement; 39 per cent was cleared before 1972. The 3 most heavily cleared communities (mallee with a tussock grass understorey, brigalow and temperate tussock grasslands) together previously covered more than 170,000 square kilometres of Australia, and each has lost more than 80 per cent of its original extent (Tulloch et al. 2015).

In the past 5 years, land-clearing rates have stabilised in all states and territories, except Queensland, where clearing increased. In 2013, major changes to the Queensland Vegetation Management Act 1999 were introduced to allow landholders to clear vegetation not cleared since 31 December 1989 or land that is suitable for economically viable agricultural development. Clearing of woody vegetation, primarily for pasture, increased by 73 per cent in 2012–13 from 2011–12 and by a further 11 per cent from 2012–13 to 2013–14 (DSITI 2015).

The legacy effects of past clearing mean that the associated impacts on biodiversity are not decreasing. High rates of population growth in urban and peri-urban areas result in continued conversion and degradation of the surrounding natural ecosystems. Urban and peri-urban expansion into greenfield sites have been a significant pressures on the extent of native vegetation in southern, eastern and south-western Australia (e.g. banksia woodlands in south-western Australia), and on high-value agricultural floodplains around regional cities and near the coast. Since 2011, loss of valuable agricultural lands continued across most states and territories because of urban encroachment.

Although the extent and effects of land clearing and habitat fragmentation can be measured, no national-scale metric exists for habitat degradation—surrogates such as soil acidification and water quality are used instead. Habitat degradation is dealt with in the relevant sections of the SoE thematic reports (see, for example, sections in the thematic reports on erosion, salinisation, soil acidification, water quality, livestock production, habitat degradation in the pastoral zone, and invasive species).

Jackson WJ, Argent RM, Bax NJ, Bui E, Clark GF, Coleman S, Cresswell ID, Emmerson KM, Evans K, Hibberd MF, Johnston EL, Keywood MD, Klekociuk A, Mackay R, Metcalfe D, Murphy H, Rankin A, Smith DC, Wienecke B (2016). Overview: Land-use change, and habitat fragmentation and degradation threaten ecosystems and resilience. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/theme/overview/topic/land-use-change-and-habitat-fragmentation-and-degradation-threaten-ecosystems, DOI 10.4226/94/58b65510c633b