Geography. Tree line shifts.

  title={Geography. Tree line shifts.},
  author={Elizabeth Pennisi},
  volume={341 6145},
Repeat photography is helping reveal when a warmer climate is affecting vegetation—and when it isn’t. In the American Southwest, work by Robert Webb, a plant ecologist recently retired from the U.S. Geological Survey in Tucson, Arizona, has shown that fewer, shorter freezes are paving the way for more cactus seedlings and certain frost-sensitive shrubs to… CONTINUE READING