Koalas and biodiversity – when multiple regression analysis helps

A couple of days prior to being re-elected, NSW Premier Mike Baird announced his government will adopt all 43 recommendations of  the Bio-diversity review.  The response from conservation groups was generally less than supportive and has prompted the Nature Conservation Council to launch a campaign to ‘save the koala‘ . The idea being to “pull together the latest science and on the ground land managers to drive the next generations of laws to save the koala and other wildlife.”

Interestingly the Biodiversity review took its understanding of threats to native species and populations from a paper titled “The threat posed by pest animals to biodiversity in New South Wales”(2007), produced by the former Office of Environment and Climate change, in collaboration with the Invasive Animals Cooperative Research Centre, Canberra. This was prior to BMAD being listed as a key threatening process. Dieback is referred to twice in the paper, in association with the Noisy minor and ‘undetermined’. There are also several references made to the uncertainty around climate change, as well as the impacts of increasing inland salinity. The latter being closely related to soil sodicity in coastal forests.

berridale rainfall
The graph above is from the previously referred to Monaro dieback summary, where the reduction of autumn rainfall over the past twenty years is thought to be the final factor pushing trees over the edge. However, if we were looking for factors that are known to have a negative influence on soils, the increased rainfall during summer is arguably more important.

Where things become problematic is the weighting one places on different negative impacts, like the loss or reduction of ecological processes. Long term research in the Amazonian rainforest, led by scientists from the University of Leeds, has found a ‘one-third decline in the rainforest’ growth overall’.

The research undertaken over 30 years has ‘found increased tree death, but also increasing growth of vines, which are flourishing in the disturbed forest environment that occurs when trees die at a greater rate.’ The shift in growth from trees to vines was thought to be associated with unprecedented droughts, not associated with and in addition to, El nino related drought.

Like tree decline on the Monaro, adjacent coastal agricultural lands and ‘wet eucalyptus forests’, ‘the study shows that the decline in the rainforest’s carbon-dioxide-absorbing capacity predates these extreme droughts’.

Thankfully a weighting can be placed on soil materials, and ‘multiple regression analysis’ tells us that biodiversity is what maintains them in a condition conducive to growth and carbon sequestration.


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