About 26 glaciers remain from the 150 that were here in 1850, and that number is dropping steadily. If the weather is clear, five glaciers can still be seen in Many Glacier Valley, but climate change is altering both the visible and less visible features of the park, and in just a couple of decades the view from this spot may look dramatically different. As climate warms, rainfall and snowfall are also likely to change, affecting soil moisture, runoff, stream flow, and landscape disturbance processes such as fire and avalanches, with consequences for park ecosystems. Climate helps determine what flora and fauna can exist in a habitat because every species has a temperature range in which it can thrive. Treeline, the elevation where trees stop growing, is strongly related to temperature and moisture, and as climate warms, trees will encroach on alpine meadows and treeline will move to higher elevations. Changes in forests and other vegetation may cause animals to seek higher ground or migrate north to find suitable habitat, and in cold alpine environments, some species may not survive. Over the last 100 years, the Earth's surface temperature has increased about 1.5 degrees Fahrenheit, with accelerated warming in the last few decades; since the 1970s temperatures have been markedly warmer than earlier in the 20th century, and the six hottest years on record were 2005, 1998, 2002, 2003, 2006, and 2004. Some effects of climate change may not be fully understood, but the landscape seen today will look different in the future.