New studies confirmed that the current warming period is without precedent in the past two thousand years. Permafrost in the Canadian Arctic is thawing seventy years ahead of schedule, nitrous-oxide emissions from Arctic permafrost are twelve times higher than expected, and it was feared that existing models may underestimate underwater glacial melt by two orders of magnitude. Wildfires ravaged the Arctic, a meltwater lake appeared at the North Pole, and a European heat wave caused the loss of 12.5 billion tons of Greenlandic ice in a single day, as well as record-high temperatures for several countries, including Britain, where the warming climate has enabled the arrival of the black bee fly (Anthrax anthrax), the Jersey tiger moth (Euplagia quadripunctaria), and the purple heron (Ardea purpurea). Only 38 percent of remaining tropical forests have a sufficiently wide latitudinal range to allow animals to move to cooler regions as the earth warms. A U.S.–Russian team found that even a mild warming scenario will increase the habitable area of Siberia several times over. The “early warming” period, from 1915 to 1945, was caused by external factors and not, as previously thought, by natural changes in ocean temperatures. Climate change was expected to make staple crops less nutritious and to lower the global availability of protein by a fifth, and may alter the mating calls of male weakfish. The Great Atlantic Sargassum Belt is now a recurring feature of the ocean.