As global warming proceeds the frozen arctic tundra will turn into forest or grass lands. In just a few decades shrubs in the Arctic tundra have turned into trees as a result of the warming Arctic climate, creating patches of forest which, if replicated across the tundra, might accelerate global warming. Scientists from Finland and Oxford University investigated an area of around 100,000 square kilometers, known as the northwestern Eurasian tundra, stretching from western Siberia to Finland. Surveys of the vegetation, using data from satellite imaging, fieldwork, and expert observations from indigenous reindeer herders, showed that in 8-15% of the area willow (Salix) and alder (Alnus) plants have grown into trees over 2 meters in height in the last 30-40 years.