CSIRO: Landscape is biggest carbon sink

New research published by the CSIRO has found that Australia’s landscape is by far the country’s largest carbon sink. However, its nowhere near enough, absorbing just one-third of the national fossil fuel emissions over the last 30 years.

The research, published in the open-access Biogeosciences (abstract here with link to full PDF of the paper), also found that Australia is now exporting 2.5 times as much carbon and CO₂ as it emits, in the form of its coal and gas fossil fuel exports.

Those “carbon exports” rose very quickly in the two decades covered by the study: in 1990, Australia only exported 1.5 times as much fossil fuel as it used locally.

When the variation in plant uptake of carbon – for example, under different weather conditions – is taken into account, plans in Australia soak up an annual average of 2.2 billion tonnes of carbon annually. In the modern era, the researchers say, plants have expanded their carbon uptake – but only by about 15 percent compared to pre-industrial times.

Moreover, that uptake is hugely variable. As lead author Dr Vanessa Haverd of CSIRO Marine and Atmospheric Sciences notes in the agency's announcement, the carbon stored in plants during high rainfall will be released in the next drought.

The work focussed on calculating the total emissions budget for the years 1990-2011 using the BIOS2 and CABLE models, as part of a global regional assessment called RECCAP (Regional Carbon Cycle Assessment and Processes).

There are some snippets of good news in the research. Increasing rainfall in some regions is driving more vegetation in desert areas, for example. The research states: “One extreme was the desert region, where CO2 fertilisation reinforced the positive impact on NEP of extremely high rainfall in 1990–2011, preceded by several decades of increasing rainfall.”

However, in cool, temperate regions, “CO2 fertilisation was only just sufficient to offset the negative impact of decades of drought.”

The aim of the research is to help reconcile different approaches to estimating the global carbon budget – “bottom up” estimates such as this on the one hand, and “top down” estimates based on measurements of atmospheric carbon. ®