Agence France-Presse: Land ecosystems will have to move hundreds of metres each year in order to cope with global warming, according to a letter published on Thursday in Nature, the British-based science journal. On average, ecosystems will need to shift 420 metres (about a quarter of a mile) per year to cooler areas this century if the species that inhabit them are to keep within their comfort zones, scientists in the US believe. Flat ecosystems such as mangroves, wetlands and deserts face the …