The mighty kelp forests off California’s coast are highly valued as biodiverse ecosystems essential for sequestering carbon, but they have been hit hard by a range of different foes, including the ravages of heat waves, destruction by fishing and armies of voracious sea urchins. In the past century kelp forests have declined by up to 75 per cent in some areas, but new research from the University of California at Santa Cruz reveals otters may be...