10 December 2015, Science Daily, Trees either hunker down or press on in a drying and warming western US climate. In the face of adverse conditions, people might feel tempted by two radically different options — hunker down and wait for conditions to improve, or press on and hope for the best. It would seem that trees employ similar options when the climate turns dry and hot. Two University of Washington researchers have uncovered details of the radically divergent strategies that two common tree species employ to cope with drought in southwestern Colorado. As they report in a new paper in the journal Global Change Biology, one tree species shuts down production and conserves water, while the other alters its physiology to continue growing and using water. As the entire western United States becomes warmer and drier through human-made climate change, these findings shed light on how woody plants may confront twin scourges of less water and hot weather. The authors, UW biology graduate student Leander Anderegg and biology professor Janneke Hille Ris Lambers, wanted to understand if different tree species employ similar coping strategies for drought, and how these strategies would affect their future ranges in a warmer and drier climate. They compared how two common tree species differ in terms of shape, growth rate and physiology across wet and dry portions of their native ranges. “We really wanted to identify the entire suite of strategies that a plant can use to grow in drier environments, as well as which of these strategies each tree would employ,” said Hille Ris Lambers. Read more here
13 November 2015, Climate News Network, Global warming drains the water of life. Melting snowpack in Turkey’s Lesser Caucasus mountains. New research warns that rising temperatures are reducing the mountain snow on which billions of people in lowland areas depend for their water supply. Up to two billion people who depend on winter snow to deliver their summer water could see shortages by 2060 as upland and mountain snowpacks continue to dwindle. An estimated 300 million people could find, 45 years on, that they simply won’t have enough water for all their needs, according to new research. Climate change driven by rising atmospheric levels of carbon dioxide – in turn, fed by human combustion of fossil fuels – may already be affecting global precipitation. Researchers have consistently found that much of the world’s drylands will increase as global average temperatures rise. But warmer temperatures increasingly also mean the water that once fell as snow, to be preserved until the summer, now falls as winter rain, and runs off directly. The snow that does fall is settling at ever higher altitudes and melting ever earlier. Reliable flow This is bad news for agricultural communities that depend on a reliable flow of meltwater every summer. California is already in the grip of a sustained drought, made worse by lower falls of snow. Great tracts of Asia depend on summer meltwater from the Himalayan massif and the Tibetan plateau. Justin Mankin, an environmental scientist at Columbia University’s Earth Institute in the US, and colleagues report in Environmental Research Letters journal that they studied 421 drainage basins across the northern hemisphere. Read More here