Modelling impacts of vegetation cover change on regional climate

Climate change is now the major and most urgent environmental issue facing Australia. Australia is particularly vulnerable to climate change, as it will compound existing land use pressures on natural resources, agriculture and native ecosystems. Australia’s current policy response to climate change has focused on mitigation and adaptation of forecasted changes attributable to greenhouse gas emissions. However, these responses do not include the two-way interactions and feedbacks of the land surface on climate.

New analytical techniques have enabled models to detect the impact of clearing relative to global atmospheric changes and this was reported in the Canberra Times (9 Feb 2008).
The CSIRO Mark 3 climate model was used to run simulations using pre-European and 1990 vegetation cover to reconstruct climate for the period 1951-2003. This enabled the comparison of “pre-European vegetation” and “1990 vegetation and crops”. The simulation explained the instrumental trend since 1950, of a statistically significant increase in annual and seasonal surface temperatures for eastern Australia (0.4-2°C) and southwest Western Australia (0.4-0.8°C) with a pronounced summer increase. The climate model controls for other factors and in this way it mimicked the instrumental model to provide evidence of a probable causal link between regional scale vegetation clearing and climate change.

Areas that had most extensive clearing (southwest Western Australia) also had mean summer rainfall decreases of 4-12% in eastern Australia and 4-8% in southwest. Increases in the model and on ground of an average 2°C in southern Queensland and New South Wales for the 2002/2003 drought indicates the link between large scale clearance of native vegetation and temperature. This appears to be amplifying the adverse impacts associated with El Niño drought periods and makes clearing potentially an important contributing factor to the observed changes in regional climate of Australia.

Work is continuing to develop and refine the approach to improve the downscaling of vegetation and climate interactions. The latest analyses establish the magnitude and distribution of impacts on ocean and air circulation.

Project objectives

• Refine existing conceptual model of land surface-atmosphere interactions and feedbacks developed by Lawrence (2004), with a specific focus on regional-scale processes and feedbacks.
• Model the sensitivity of continental and regional climate to imposed woody and herbaceous land cover characteristics using CSIRO GCM climate models, addressing the following:
• Evaluate the impact of pre-European and modern land cover characteristics using an ensemble of 10 simulations each for the period 1949-2005, and the strength of the ENSO impact for the two land cover change scenarios;
• Test the sensitivity of the magnitude of land cover change in order to identify threshold changes in regional climate with an emphasis of hydrological cycle;
• region, thereby increasing our confidence in robustness of the sensitivity of model results to historical land cover changes;
• Analyse the results of CLIMATE OF 20th CENTURY project, evaluate the relative contribution of different radiative forcings to climate change signal in regional Australia, with a specific emphasis on comparing the relative importance of land cover change; and
• Review the potential relevance of the outcomes of Objective 2 for natural resource management and policy.
    

Implications

The research provides evidence of a probable causal link between regional scale vegetation clearing and climate change and suggests clearing is potentially an important contributing factor to the observed changes in regional climate of Australia.

The authors suggest that policy needs to recognise that climate change is a two-way process, and that broad scale clearing of native vegetation cover has a strong influence on climate in addition to greenhouse gases.

Protecting and restoring Australia’s native vegetation therefore needs to be a critical policy and management consideration in mitigating the effects of climate change.
  

Publications and Resources

None listed

Citation

Land & Water Australia. 2009. Modelling impacts of vegetation cover change on regional climate. [Online] (Updated June 24th, 2009)
Available at: http://lwa.gov.au/node/2946 [Accessed Tuesday 26th of April 2011 02:44:10 PM ].