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Issue: Direct pressure of human activities on the land - Land clearing

This is an issue under the Land theme of the Data Reporting System.

Why we need to know about this issue

Generally, the pressures that affect the condition of the land do so by affecting the condition of the things that live in and on it, and the pressures that affect the condition of terrestrial biodiversity do so by affecting the condition of the land on which life depends for habitat and survival.

As land cover is crucial to land condition, land clearing is a very significant pressure on land condition. Removal of vegetation for various human purposes exerts pressure on the remaining vegetation and everything else that lives in it by removing its habitat.

Removal of vegetation also leaves soil bare (unstable) and vulnerable to erosion. Soil stability is essential to land health and soil erosion is a very significant pressure on land condition because it undermines existing vegetation and habitats and inhibits vegetation and other biota that inhabit the vegetation from re-establishing themselves.

Another way in which removal of terrestrial vegetation for various human purposes exerts pressure on other biota is by removing a source of nutrient replenishment. If vegetation is removed, there is less biological matter available to break down and replenish the nutrients in the soil. Exposing soil to erosion leads to further nutrient depletion. Loss of nutrients from the land can be facilitated by the removal of original vegetation, or of the crops or animals that graze on the vegetation, and can ultimately impact back on vegetation and other life forms through a reduced capacity of the soil to sustain life.

A further way in which land clearing places pressure on the land is by interfering with hydrology, with potential impacts on water availability that may be further reaching than the actual area cleared. One of these far-reaching impacts is dryland salinity. Ground water in Australia can be very saline but deep-rooted vegetation absorbs it so that it does not rise to the surface and mix with surface water. Removal of deep-rooted vegetation reduces this absorption, allowing the saline water to rise, causing salt contamination of the surface soil. Dryland salinity exerts pressure on the land because it inhibits the recovery or re-establishment of vegetation (either natural or crops for human use).

Removing vegetation also damages the microclimate by removing shade and reducing humidity, and contributes to changes to the global climate by diminishing the capacity of the world’s vegetation to absorb carbon dioxide.

Indicators

• LD-01 The proportion and area of native vegetation and changes over time 
  While all the original vegetation cleared in Australia was, by definition, native vegetation, it is the perennial, deep-rooted, woody vegetation which is most significant in terms of providing habitats for other biota and protecting soil, micro-climate and water catchments. It is this type of vegetation that has seen the most significant reductions since the European invasion. Extent and change in vegetative cover show the extent of these reductions.
• LD-03 Change in extent and proportion of woody vegetation, clearing and regrowth 
  Woody vegetation is generally perennial and deep-rooted, providing year-round habitat for other biota and protecting soil, micro-climate, groundwater and water catchments. It is woody vegetation that has seen the most significant reductions since the European invasion. Extent and change in extent, clearing and regrowth of woody vegetative cover is a direct indicator of the pressure of land clearing on land condition.
• LD-17 Fragmentation of remnant vegetation 
  While the gross area of land cleared is one indicator of the pressure of vegetation removal on the land’s general condition, the health and resilience of the vegetation that remains are also largely dependent on the size of the fragments and their distance from each other.
  The smaller and more isolated the remnants, the greater the threat from external pressures as their boundaries (representing a increasing proportion of total area with decreasing fragment size) are exposed to disturbances Pressure also increases with the distance to be traversed to other refugia by animals (including pollinators), seeds, soil nutrients etc.
• LD-20 Total grazing pressure relative to net primary productivity 
  Although grazing is primarily an issue arising from the pressure of introduction of new species to the land (pasture, in some cases, exotic pasture, replacing native vegetation and introduced animals replacing native animals), overgrazing also has the potential to completely remove ground cover, leaving bare soil. The indicator gives a spatial indication of where this is most likely to happen.
• BD-13 Examples of the impact of grazing on biodiversity 
  Although grazing is primarily an issue arising from the pressure of introduction of new species to the land (pasture, in some cases, exotic pasture, replacing native vegetation and introduced animals replacing native animals), overgrazing also has the potential to completely remove ground cover, leaving bare soil. The indicator gives a spatial indication of where this is most likely to happen.

Related issues

• Land - Land condition- Land cover 
• Land - Land condition- Soil stability and quality 
• Land - Land condition- Condition of terrestrial species and ecological communities 
• Land - Direct pressure of human activities on the land- Soil loss and loss of soil quality 
• Land - Direct pressure of human activities on the land- Land clearing 
• Land - Contributions and pressures between the land and inland water- Pressures of changes to the land on inland waters 
• Land - Societal responses- Responses to vegetation loss, carbon loss, species loss and species change 
• Land - Contributions and pressures between the land and the atmosphere- Climate 
• Land - Contributions and pressures between the land and the ocean- Condition of species at the land-ocean interface 
• Land - Contributions and pressures between the land and inland water- Pressures of changes to inland waters on land 
• Biodiversity - Landscapes- Ecosystem diversity 
• Biodiversity - Pressures on biodiversity- Land clearing 
• Biodiversity - Species, habitats and ecological communities- Conservation status of species and ecological communities 
• Atmosphere - Climate variability and change- Greenhouse 
• Inland Waters - Habitat scale influences- Riparian vegetation 
• Inland Waters - Catchment scale influences- Land and vegetation condition- Vegetation