The rats of Lord Howe: What kind of biodiversity is achieved through biocide?

No evidence has yet surfaced that humans had ever set foot upon the tiny, isolated portion of the inhabitable earth now known as Lord Howe Island until Lieutenant Henry Lidgbird Ball, commander of H.M.S. By the mid-1930s, or very shortly thereafter, five more unique native birds had gone the way of the gallinule, the pigeon and the parakeet: the Lord Howe fly-eater, the Lord Howe fantail, the robust silver-eye, the Lord Howe starling, and the ouzel or “doctor bird.” Granted, some of these – such as the ouzel, which had been common as recently as 1906 – had already significantly declined due to human disturbance and the predation of other introduced species, but the arrival of the rats seems to have been their death knell. “In an effort to check the increase of the rats,” writes Hindwood, “almost one hundred owls of several kinds were sent to the island between 1922 and 1930.” There was already a native owl on the island – ninox novaeseelandiae albaria, the Lord Howe boobook – but the arrival of the imported owls appears to have hastened this bird’s disappearance. Although, as we’ve just seen, the rodent numbers seem to have long since stabilised, and, for better or for worse, the rats and mice could be argued to have created and now occupy an ecological niche – although the most endangered birds seem to have been brought back from the brink, the last rat-induced extinctions are now eighty to one hundred years in the past, and the rest of the remaining indigenous bird species seem to be in very healthy numbers indeed – 360,000 rodents are to be exterminated. As for the Tasmanian masked owl, according to a logic I find it difficult to follow, on Lord Howe, an invasive species, they’re condemned not so much for what they’ve done as for what they might do – develop a taste for tree lobsters – if ever the rat problem is solved and dryococelus australis is able to return.