Saguaro cacti in the Sonoran Desert near Tucson, Arizona, USA

Sky island views

December might be chilly here in the UK - but over in the US state of Arizona, the Sonoran Desert stays warm all year round. In this photo, we’re looking at a 'sky island' - an isolated woodland, high above sea level, surrounded by very different lowland environments. In this case, the desert land at the base of the mountain is peppered with saguaros, a stately cactus recognised by its long arms. The snow-capped Santa Catalina Mountains in the distance are part of the Madrean Sky Islands and are home to Mount Lemmon Sky Valley, the southernmost ski destination in the US. Mount Lemmon reaches 9,150ft at the summit and gets about 15ft of snow annually.