Wind erosion in Australia

clankflaxMechanics

Feb 22, 2014 (3 years and 5 months ago)

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Wind erosion in Australia


Introduction

Wind erosion is the process by which soil is detached and transported from the land surface by the
action of wind. T
he speed of the wind must exceed a threshold to move sediments; large particles
(>90µm) are
usually the first to move, hopping along the soil surface. As large particles bounces off
the surface more sediment is disturbed and released into the airstream.

The ejected fine particle
fraction (<20µm) ‘dust’ can travel great distances. Australian dust
has been tracked to New Zealand
and Antarctica. Dust contains carbon and clay which hold the bulk of soil nutrients. Dust emission
depletes soil nutrients at the source (where the dust originated) and enriches soils where dust is
deposited. Dust deposed in

unwanted places, e.g. on vegetable crops is a major source of pollution.

Soils have different susceptibilities to wind erosion. Sandy soils common to the Mallee or desert
loam soils are highly vulnerable to wind erosion. This is attributed to their low so
il aggregation,
variable soil moisture and tendency to disaggregate with disturbance (e.g. cultivation). In contrast,
highly aggregated soils such as black earths and ferrosols have a low susceptibility due to their
higher aggregation levels.

Low rainfall
areas tend to be more susceptible to wind erosion; in wetter
areas higher levels of soil moisture promote vegetation growth, increase the binding capacity of soil
particles and encourage the growth of microorganisms which produce protective soil crusts.

W
ind erosion hazard has been identified as a key indicator of the condition of Australia’s soils
(National Land and Water Resources Audit 2007). Wind erosion is a natural process, exacerbated by
land management practices. Dust is generated from natural and
agricultural landscapes; e.g. land
managed for conservation where ground cover is naturally low, such as the margins of Lake Eyre;
dust is lost from agricultural lands when management decisions that affect the percentage of ground
cover retained and the so
il aggregation level have not taken into account climatic conditions.


The impact of wind erosion

Onsite impacts of wind erosion include soil loss, particularly the finer fractions of clay, carbon
(Chappell et al, 2012) and fertiliser (Leys and McTainsh
1994), which affects productivity, plus
damage to infrastructure, such as fences and roads. Off site impacts include sedimentation of dams
and rivers, reduced air (Leys et al, 2011) and water quality (Leys and McTainsh, 1999), including
increased eutrophic
ation (Shaw et al, 2008), disruptions to electricity supply and aviation (Williams
and Young 1999), increases in respiratory problems and cleaning costs (Tozer and Leys, 2013),
changes to Australia’s rainfall (
Rotstayn
et al. 2012) and to global climate th
rough radiative forcing of
dust (
Mahowald et al, 2010
).


The September 2009 (Red Dawn) dust storm brought dust from the Lake Eyre Basin in South
Australia and Queensland and from the far west and north west of New South Wales to the entire
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eastern seaboar
d. Sydney, Brisbane and Townsville were all heavily impacted upon. An estimate of
2.54 million tonnes of soil was lost off the east coast in this one event (Leys et al, 2011). An
economic assessment of the impact on the NSW economy alone estimated the cost

of the resulting
disruptions and clean up required as $299 million (Tozer and Leys 2013).


This included increased cleaning costs of $255 million, losses to the construction $2.4 million, retail
and services sector ($10 million), transport sector losses
of $11 million, and soil fertiliser and carbon
losses to landholders of $13 million. Preliminary modelled estimates suggest that soil was lost from
780,000 km
2

(about 19 per cent of Australia) in this event; an estimated 60 per cent of South
Australia lost

soil (Butler et al, unpublished). Regional dust storm events are more frequent, their
economic impacts are generally lower because populations are smaller and regions have fewer
infrastructure assets. Estimates of the offsite impacts of dust erosion on Mi
ldura show that costs to
the regional economy are approximately $3 million annually (Tozer and Leys 2013).


The extent of wind erosion

Large dust storms occurred during the Millenium drought (Figure 1). However, as noted in the 2011
State of the Environme
nt Report, wind erosion activity over this period was substantially less than
that during the 1940s “dustbowl” years. Wind erosion is an ongoing concern. Figure 2 shows the
extent of wind erosion in 2008
-
09; it is estimated around 47 per cent of Australia

lost soil through
wind erosion in this period. Circumstances which encourage sustainable land management have
improved greatly, but not all land holders have adopted these management practices, and it is for
this reason that accelerated wind erosion stil
l occurs. Furthermore, even if all the sustainable
management practices available are adopted, climate changes and extreme weather events will
continue to test land management systems.




Figure 1 Bar chart showing modelled annual estimates of the perc
entage of Australia with
observable net soil loss due to wind erosion 2000
-
01 to 2010
-
11. (“Observable” wind erosion can be
readily detected in the landscape. Lower levels of erosion, only detectable by detailed examination
of the soil surface could be occ
urring. Source: H. Butler, pers. comm.


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Figure 2 Map showing the modelled area of Australia with observable wind erosion in 2008
-
09.
Source: H.Butler, pers. comm.

Monthly estimates of wind erosion are reported at www.dustwatch.edu.au .


Land management

practices strongly influence erosion regardless of climate conditions. Wind
erosion levels increase dramatically when ground cover levels (the percentage of soil covered by
vegetation) drop below 50 per cent (Leys 1999). Land management practices that lea
d to
overgrazing and excessive cultivation of ground cover can result in cover levels below 50 per cent,
and during drier periods this increases the likelihood of wind erosion (Figure 3). In wet periods bare
ground due to cultivation of cropland can also l
ead to wind erosion. In February 2012 the largest
dust event in NSW since early 2010 was associated with burning and cultivation of cropland, which
resulted in low ground cover levels in north west Victoria and far south west New South Wales
(Office of Env
ironment and Heritage 2012,
http://www.environment.nsw.gov.au/resources/dustwatch/DWNL120430.pdf).



Figure 3: Graph showing the Relationship between wind erosion and percentage ground cover.
Arrow indicates the 50 per cent ground cover target required to

control wind erosion (Sources: Lang
1979 and Leys 1999).


0
20
40
60
80
100
0
20
40
60
80
100
Ground cover (%)
Av. annual soil loss (t/ha)
0
20
40
60
80
100
0
20
40
60
80
100
Ground cover (%)
Soil transport rate (g/m/s)
4



Figure 4 Photo showing paddock with 50 per cent cover level, adequate to control wind erosion (J.
Leys 2013).


Reducing wind erosion

Ground cover management practices have a major role in reduci
ng wind risk on agricultural lands
(Figure 4). In the broadacre cropping industries, ground cover management practices (tillage and
stubble management) have improved considerably since 1995; it is estimated that for 2009
-
10
around 76 per cent of cropland w
as prepared without cultivation and crop residue was retained on
68 per cent of cropped land (Barson et al. 2012a). However, significant levels of stubble burning and
cultivation are evident on satellite imagery used to monitor ground cover and track dust
plumes;
increases in stubble burning and cultivation may be a response to increases in pests, diseases and
weeds and heavy stubbles associated with recent wetter seasons in some regions (see DustWatch
February and April 2012 reports http://www.environment.
nsw.gov.au/dustwatch/dwreports.htm)


Monitoring ground cover levels in paddocks and using ground cover targets (the desired percentage
of soil covered by living or dead vegetation) to manage stock movements helps protect the soil from
increased rates of lo
ss via wind and water erosion. Maintaining good ground cover levels also
improves drought resilience by helping pastures respond quickly to rain. In the grazing industries
awareness of the importance of ground cover management has increased over the period

2008
-
09
to 2009
-
10, from 72 to 88 per cent in the dairy industry and 70 to 79 per cent in the beef
cattle/sheep industries (Barson et al. 2012b). Further work is required to encourage grazing
businesses to set ground cover targets and manage to these to e
nsure that cover levels are sufficient
to prevent soil loss through erosion.


Monitoring wind erosion

Caring for our Country, the Department of Agriculture, Fisheries and Forestry and NSW, Victorian,
South Australian and Western Australian state agencies
and some natural resources management
regions, Griffith and Southern Queensland universities are collaborating to develop an integrated
approach to monitoring wind erosion. This includes ground based surveys of erosion status for
regional and state reporti
ng and to calibrate national wind erosion modelling, the NSW Office of
Environment and Heritage Community DustWatch program which reports monthly on dust activity
at ground based stations in NSW, northern Victoria, South Australia and southern Western Aust
ralia
http://www.environment.nsw.gov.au/dustwatch/dwreports.htm , satellite monitoring of ground
cover by ABARES, CSIRO, state and territory agencies (http://www.daff.gov.au/natural
-
resources/soils/monitoring/ground
-
cover
-
monitoring
-
for
-
australia and repor
ting of regional wind
erosion histories by Griffith University (www.dustwatch.edu.au). These projects contribute to the
national modelling and reporting of soil erosion loss undertaken by OEH and the University of
Southern Queensland (www.dustwatch.edu.au
).

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References

Barson, M. Mewett, J., and Paplinkska, J. (2012a) Land management practice trends in Australia’s
broadacre cropping industries. Caring for our Country fact sheet 3. Department of Agriculture,
Fisheries and Forestry. http://www.daff.gov.au/_
_data/assets/pdf_file/0006/2148711/national
-
factsheet
-
farm
-
practices
-
broadacre.pdf


Barson, M. Mewett, J., and Paplinkska, J. (2012b) Land management practice trends in Australia’s
grazing (beef cattle/sheep) industries. Caring for our Country fact sheet 2
. Department of
Agriculture, Fisheries and Forestry.
http://www.daff.gov.au/__data/assets/pdf_file/0009/2148714/national
-
factsheet
-
farm
-
practices
-
grazing.pdf


Barson, M. Mewett, J., and Paplinkska, J. (2012c) Land management practice trends in Australia’s
dairy industry. Caring for our Country fact sheet 1. Department of Agriculture, Fisheries and Forestry.
http://www.daff.gov.au/__data/assets/pdf_file/0008/2148713/national
-
factsheet
-
farm
-
practices
-
dairy.pdf


Butler, H., Leys, J., Strong, C., and McTainsh
, G. (unpublished) Caring for our Country Wind erosion
extent and severity maps for Australia. Milestone 5 progress report. May 2012.


Chappell, A., Sanderman, J., Thomas, M., Read, A., and Leslie, C., (2012) The dynamics of soil
redistribution and the im
plications for soil organic carbon accounting in agricultural south
-
eastern
Australia. Global Change Biology (2012), doi: 10.1111/j.1365
-
2486.2012.02682.x


Lang, R. D. (1979) The effect of ground cover on surface runoff from experimental plots. Journal of
the Soil Conservation Service of NSW, 35(2), 108
-
114.


Leys, J. F. (1991) Towards a better model of the effect of prostrate vegetation cover on wind erosion.
Vegetatio, 91, 49
-
58.


Leys, J. F. (1999). Wind erosion on agricultural lands.
In

'Aeolian Enviro
nments, Sediments and
Landforms'. (Eds. Goudie, A. S., Livingston, I, and Stokes, S.), pp. 143
-
166. (John Wiley and Sons,
England).


Leys, J. F., and McTainsh, G. H. (1994) Soil loss and nutrient decline by wind erosion
-

Cause for
concern. Australian Jour
nal of Soil and Water Conservation, 7(3), 30
-
40.


Leys, J. F., Heidenreich, S. K., Strong, C. L., McTainsh, G. H., and Quigley, S. (2011) PM10
concentrations and mass transport during “Red Dawn”
-

Sydney 23 September 2009. Aeolian
Research, 3(327
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342), 10.
1016/j.aeolia.2011.06.003.


Leys, J. F., and McTainsh, G. H. (1999) Dust and nutrient deposition to riverine environments of
south
-
eastern Australia. Zeitschrift für Geomorphologie Supplementband, 116, 59
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76.


Mahowald, N. M., S. Kloster, S. Engelstaedter,

J. K. Moore, S. Mukhopadhyay, J. R. McConnell, S.
Albani, S. C. Doney, A. Bhattacharya, M. A. J. Curran, M. G. Flanner, F. M. Hoffman, D. M. Lawrence,
K. Lindsay, P. A. Mayewski, J. Neff, D. Rothenberg, E. Thomas, P. E. Thornton and C. S. Zender (2010)
Ob
served 20th century desert dust variability: impact on climate and biogeochemistry. Atmospheric
Chemistry and Physics
10
(22): 10875
-
10893.


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National Land and Water Resources Audit (2007) Soil condition. Indicator protocol for wind erosion
hazard.

http://lwa.gov.au/files/products/national
-
land
-
and
-
water
-
resources
-
audit/pn21419/pn21419.pdf


Office of Environment and Heritage (2012) Dustwatch report for February 2012. DW_Nat201201.
New South Wales Office of Environment and Heritage.

http://www.envir
onment.nsw.gov.au/resources/dustwatch/DWNL120229.pdf


Rotstayn, L. D., M. A. Collier, R. M. Mitchell, Y. Qin, S. K. Campbell and S. M. Dravitzki (2012)
Simulated enhancement of ENSO
-
related rainfall variability due to Australian dust (vol 11, pg 6575,
2011
). Atmospheric Chemistry and Physics
12
(3): 1481
-
1481.


Shaw, E.C, Gabric, A.J., and McTainsh G.H. (2008) Impacts of aeolian dust deposition on
phytoplankton dynamics in Queensland coastal waters. Marine and Freshwater Research, 59, 951
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962, and reply to c
omment
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, 504

506.


State of the Environment Committee (2011) Australia State of the Environment 2011. Independent
report to the Australian Government Minister for Sustainability, Environment, Water, Population
and Communities. Canberra.


Tozer, P. and
Leys, J. (2013). Dust storms


what do they really cost?
Australian Rangeland Journal
,
35
(2), (in press).


Williams, P. and Young, M. (1999) Costing Dust: How much does wind erosion cost the people of
South Australia? CSIRO Land and Water, Adelaide. 36 pp.



© Commonwealth of Australia 2013




This document is provided under a Creative Commons Attribution 3.0 Australia
(http://creativecommons.org/licenses/by/3.0/au/) licence.

Unless otherwise stated, all images in the publication are
copyrighted by their original owners. This publication (and any material sourced from it) should be attributed as: Barson,
M., 2013 Wind erosion in Australia. Caring for our Country Sustainable Agr
iculture fact sheet.

Department of
Agriculture, Fisheries and Forestry
.