When they are not commensurate!
The author sat in on a meeting with Boggabri Coal in 2011, and heard that the offsets required by the NSW Govt for the clearing of critically endangered Grassy Box Woodland (GBW) in Leard Forest had been set at six times the area impacted by the mine, however, the offsets acquired (and approved) were ‘derived grasslands’ ie. where the GBW had been completely cleared (leaving only grassland with a seedbank in the soil). All physical scientists know that eucalypts will not regenerate without intervention, such as fire (heat); smoke; sclarifying (scraping the seed with a knife). So there is little or no chance of natural regeneration on the derived grasslands.
Now Ecologist Phil Sparks has drawn this conclusion from his investigation of other offsets put in place by Boggabri Coal.
“The two properties do not provide suitable habitat for the EPBC threatened species of Swift Parrot, Regent Honeyeater, and Corben’s Long-eared bat and Tylophora linearis, at best the habitat is considered marginal for those species. And the properties do not offset the critically endangered ecological community of Box – Gum grassy woodland, of which 1,100 is, or has to be destroyed for the mines in Leard State Forest.
The vegetation mapping (done by Cumberland Ecology) of the high altitude remnants on those properties was found to be wrong, extensive areas mapped as grassy White Box – Stringybark woodland had no White Box at all, and were in fact Stringybark open forest”.