44 | MAY 2016
DIRECTIONS Australian Academy of Technology and EngineeringAustralia is often described as one of the world’s leading emit-
ters of carbon dioxide(CO 2 ) – aconsequence of our small
population, advanced economy and relatively large land area.
Crucially,Australia’s poor ranking is aconsequence of sources
and sinks from the land use and forestry sectors being included
or excluded from the National Greenhouse Gas Inventory.
A carbon sink is anything that absorbs more carbon than it
releases, while a carbon source is anything that releases more
carbon than it absorbs. Forests, soils, oceans and the atmos-
phere all store carbon, which moves between them in a contin-
uous cycle.
However, huge areas of native vegetation have not been
taken into account when compilingAustralia’s carbon budgets.
The nation has essentially reportedCO 2 emissions that have
been“measured” and directly identiiedwith human activities- rather than those that mirror Australia’s true input toCO 2
content in the global atmosphere.
A less selective and more meaningful analysis ofCO 2 luxes
would report net emissions–when all known sinks(sequestered
amounts) of CO 2 are subtracted from all known sources.
Satellite-based spectral sensors now enable net CO 2 emis-
sions to be measured with accuracy and precision.The fact that
we are an island continent adds to the integrity of the values
reported (compared with countries in Europe, for example,
where a nation’s air mass can cross borders at daily – or even
shorter – time intervals).
Two such satellites monitorCO 2 in the atmosphere today:
Japan’sGOSATand NASA’sOCO-2, which both record CO 2
from the top of theEarth’s atmosphere to its surface. The satel-
lites’ sensors integrate the net atmospheric contributions from
allCO 2 sources and sinks, with no distinction made as to
whether the recorded gas is anthropogenic or naturally occur-
ring. Clearly the concentration ofCO 2 in the atmosphere,
rather than its origin, is of most interest when monitoring it.
Prior to these space-based observations, carbonluxes derived
from ground-based measurements were problematic.This
notably applied to observations made for the land use and
forestry sectors. To determine carbonluxes in vegetation from
ield data it is necessary to obtainsequential recordings of carbon
stocks in the above-ground and below-ground components of
the vegetation, as well as in the soil supporting it.
Sampling problems are immense, particularly in native plant
communities. At any time weather patterns, vegetation age and
disturbances such as clearing, harvesting, ire and grazing can
impact thelux being estimated.
Onlyspace-based measurements can provide the robustness,
spatial coverage and sampling density andfrequency, as well as
the accuracy and precision necessary, to determine the Australia-
widelux ofCO 2.
Results fromGOSATandOCO-2 missions have been slow
to be published, but two recent data sets suggest that Australia
would be wise to embrace the technology and its outputs, espe-
cially given the signiicant budget allocations set aside by the
Australian government to buy carbon abatement contracts.
Why has the government committed up to $2.5 billion to
purchase these contracts?Theirst twooffer rounds appear to
be mostly based on modelling of native vegetation systems, with
questionable accuracy and precision surrounding the inputs.
PublishedGOSATmeasurements, along withOCO-2 sensor
data, suggest thatAustralia’s total netCO 2 emissions are much
lower than has been implied by the National Greenhouse Gas
Inventory. Averaged across years we are very likely to act as a net
sink. These conclusions are supported by convincing evidence
of increases in woody plant cover in Australia’s intact wood-
lands and shrublands.
Why pay $2 billion or more for carbon abatement contracts
with greatly limited land coverage when a spatially compre-
hensive, accurate and precise accounting of netCO 2 luxes for
all ofthe Australian continent can be derived from satellite
sensors at minimal cost to Australia’s budget?
Dr Bill Burrows FTSE is a retired Senior Principal Scientist in the Queensland Department of
Primary Industries, where he studied the ecology and management of Queensland’s grazed
woodland communities.Rethinking Australia’s Carbon Abatement Contracts
Australia’s total net CO 2 emissions are much lower than are implied by published numbers.Sign up at austscience.com
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