It is often said that the end cannot justify the means. This adage comes for the logic that an immoral act is an immoral act irrespective of when it occurs or for what reason.

The other day I witnessed an argument that left me thinking how this is adage is rarely applied.

The discussion began over a conservation problem that is becoming widespread in the eucalyptus forests of eastern Australia. Mature canopy trees are dying from infestations of sap sucking insects that proliferate to reach huge numbers sufficient to defoliate the tree. This explosion of insects and damage to leaves happens where a bird species, the bell miner, is abundant.

Rather than eat the insects, bell miners eat the sugary lurps that the scale insects use to protect themselves – it is a little like harvesting, for the insects regrow the lurp that covers them and the birds come round again.

Bell miners are aggressive birds and chase away other species. This lowers the predation rate on the insects that, over time, means more insects. The insects feed on the leaves that eventually succumb. When the trees loose too many leaves they die back. The process has been given an acronym BMAD; bell miner associated dieback.

Bell miners do well in disturbed forests suit because they like the dense undergrowth that comes when a forest is altered by fire, logging or other human interference.

Once established the best way to slow the spread of BMAD is active management involving the removal of shrubs. This means suppression through mechanical means, sometimes fire or, more usually, the application of herbicides.

These are drastic interventions of the kind that the conservation movement opposes with religious fervor. Only BMAD is far worse. So even among the ardent conservationists it has been accepted that intervention to remove shrubs is necessary. It is acceptable to manage with interventions of herbicide a habitat that was disturbed.

All good so far. The argument came of over the next issue.

Someone made the comment that ecologically endangered communities could be managed for improvement.

‘No, no, no you cannot do that’ was the indignant cry. ‘You cannot mess with an EEC, you just can’t.’

It was seen as a morally abhorrent suggestion. If something is designated as endangered it is suddenly untouchable.

But why not actively manage? Is it not exactly the same as the intervention proposed to tackle BMAD. In that thorny issue the end justified the means. But the same means cannot be applied to an EEC.

So in the real everyday world we have selective morality.

No surprise perhaps, but it makes you wonder what grounds our logic if its not a sense of morals.