much colder because of wind chill in windy or wet conditions. Precipitation is distributed fairly evenly over all months of the year, and mostly originates from a westerly airflow. There is, however, significant variation in precipitation with altitude. For example, Chamonix has an elevation of approximately and receives around of annual precipitation, whilst the Col du Midi, which is at above sea level, receives significantly more, totalling . However, at an even higher altitude (near to the summit of Mont Blanc) precipitation is considerably less, with only around recorded, despite the latter measurements being taken at a height of . In the mountains further south of the Mont Blanc range, annual precipitation is significantly less than at equivalent altitudes within the massif. For example, the valleys in the Pelvoux massif at around receive only around of precipitation per year, which is significantly less than that in either Courmayeur or Chamonix. Ecology The massif contains a very rich variety of biodiversity as a result of the huge height range and different habitats found between the valleys and the highest summits. Mild temperatures occur at altitudes between , whereas arctic conditions occur from up to the highest point at . Whilst the Mont Blanc massif does not contain any species that are endemic to it, there are many rare and legally protected species found within its four major habitat zones. These are the: montane forests, sub-alpine, alpine and nival zones. The major habitats are coniferous forests, moors, rock and talus slopes, plus glacial moraines. The biological richness is further influenced by the different aspects of the faces, by the geology, and by the influence of man on the lower and middle slopes where forest clearance has created open grassland. The native forest habitats are essential for the survival of many species, with the key conifer species including larch, pine, stone pine and red pine. Flora Over a thousand plant species have been recorded across the massif, from the valley bottoms right up to where the alpine chrysanthemum () can be found at a record-breaking height. Early explorers, such as Alexander von Humboldt in 1807, observed a number of notable species in the mountains around Mont Blanc at altitudes above . This was well above the permanent snow line, but on rocks that were so steep that little snow could rest. These arctic-alpine species included: ; ; ; Cardamine bellidifolia; Draba hirta; and