Over the southern hemisphere's summer, mercifully now at an end, Australia burned under a pitiless sun. Bush fires down the continent's eastern part consumed 46 macres of countryside, destroying homes, taking lives and driving rare animals towards extinction. To many Australians, the satellite pictures showing huge amounts of smoke drifting off to the east over the Great Barrier Reef seemed a threat to life in an age of manmade warming.
It turns out that high temperatures were doing great damage under the water as well. This month comes news that exceptionally warm seas have led the Great Barrier Reef, the world's biggest coral system, to suffer its third mass bleaching in five years. The bush and the reef: Australians almost define themselves by these two ecosystems, which once seemed boundless.
Coral bleaching takes place when sea temperatures rise sharply, causing the coral polyps that make up reefs to spray the algae(海藻) that generate their food via photosynthesis(光合作用). Without the coloured algae, coral soon dies, leaving the complex colonies a ghostly white. Reefs can recover from occasional bleachings: the fastestgrowing corals regenerate in a decade or so. But mass bleachings on the Great Barrier Reef are becoming ever more frequent. And the run of recent bleachings had already killed off relatively heatintolerant coral species. What is striking this year is that for the first time the bleaching extended to the southern part of the reef. There, closer to the pole, waters should be cooler. But not this year.
The biblical rains that put out the bush fires have also helped to lower water temperatures over the reef. The rains are proof to climatechange deniers that recent fires, droughts and floods are simply part of the natural cycle. They point with delight to the bush springing back to life. Yet while important habitats depend upon fire to regenerate, this summer's fires, exceptionally, destroyed temperate rainforests too. Regarding the reef, the deniers play down the damage and insist on the ability of "nature to fix nature". That is despite the accumulated effect of successive bleachings from which reefs struggle to recover.
The bush fires threw the prime minister, Scott Morrison, off balance. Holidaying in Hawaii made him look out of touch, while his Liberal Party's cosy links to oil, gas, coal and ironore interests came under closer inspection. Mr. Morrison's official "representative" to the Great Barrier Reef, Warren Entsch, a Queensland politician, points out that "bleached corals are not dead corals" and predicts that many will recover. Although he admits climate change is a concern, he once complained that "forcing" youngsters to be worried about it is a form of "child abuse". Most Australians care both about climate change and about the Great Barrier Reef—but not enough, alas, to call their government out over such ambivalence.
