Heatwaves aren't just a problem for humans. They can reshape
marine ecosystems too. Such extreme weather events will become
more common because of climate change. They can ravage land
ecosystems, but until now little has been known about their
effects in the seas. Events last year in the sea off Australia's
west coast suggest that the impact can be extreme and rapid. For
more than ten weeks beginning in January, sea temperatures were
between 2 °C and 4 °C warmer than usual along a 2000-kilometre
stretch of coast – the area's most extreme warming event since
records began. In November 2011, Daniel Smale at the University
of Western Australia in Perth and colleagues surveyed the area,
as they have done every year since 2006. The formerly pristine
and stable ecosystem had completely changed. "In less than a
year, we can have ecological switches from one kind of habitat
to another," Smale says. The ecosystem had lost complexity. The
kelp (Ecklonia radiate) that covered 80 per cent of the area,
providing a range o