It encompasses major mountain ranges including the Cascades, Sierra Nevada and the Transverse Ranges in southern California. It also includes the Klamath-Siskiyou region which bridges the coastal mountain ranges of California and Oregon and the Pacific Coast Ranges. The Region is one of the most diverse areas in the world for temperate conifers and is especially famous for having some of the most enormous conifers in the world, namely Sequoia sempervirens and Sequoiadendron giganteum. Much of the area is included in the Biodiversity Hotspot of the Californian Floristic Province and is characterised by cool, wet winters and hot, dry summers with many conifers in the coastal forests reliant on persistent summer fog. Threats in this Region include fragmentation of forests and reductions in population sizes due to historic logging and forestry management practices that favour particular species, urbanisation, grazing and the introduction of exotic pests and diseases. Many years of fire suppression and other management practices have caused high-intensity fires which has led to the loss of large areas of conifer forests. Recnt prolonged droughts have led to an increase in the extent and severity of wildfires, and to extensive outbreaks of pests and diseases.