Eastern Hemlocks Face Extinction. A Tiny Fly Could Save Them

This story was originally published on Grist, and is part the Climate Desk collaboration. It's June 1, and Nicholas Dietschler, a researcher in New York's Catskill Mountains, is standing in front a sapling of eastern hemlock about a quarter mile up a steep mountain. The evergreen is looking a bit dreadful. Its lower branches have become brittle and are dead. The balding of its upper limbs is a sign of its age. Dietschler scans the trees for stubby needles. He quickly finds what he is looking for. The spindly saplings are covered by tiny, woolly white bumps about the size of sesame seed seeds. Dietschler moves his thumb over the bumps. He holds up an orange-streaked finger and says that there is blood. They are alive. The ground is covered with a blue cooler, which is filled to the brim of neatly stacked plastic vials. Dietschler looks at the cooler and says that he just signed up for the next five-years of his life to work on it. Dietschler will likely be standing in front the hemlock Dietschler has just seen, and many other hemlocks in the northeastern United States before that five-year period is up. These tiny bumps are actually the eggs of the destructive woolly adelgid insect. It was smuggled with Japanese goods bound for America early in the 20th century. Since then, it has been wrecking havoc on Eastern forests. Aphid-like insects sucking sap from hemlock branches can kill trees. They can reproduce sexually and are only females. This makes them formidable enemies. The woolly adelgid is being assisted by climate change in its quest to dominate the Northeast's hemlocks. It has been spreading north into more colder climes. Already, it has destroyed millions of hemlocks in the south Appalachian Mountains. The adelgid could spread unchecked to the Northeast, and hemlocks may disappear completely. Survival of a species is dependent on its survival, and the outcome of that species' existence could be affected by the contents of the blue cool. Invasive species can be difficult to control in the absence climate change. They are especially difficult to control as the country has become warmer in winters and the climate has become more temperate. This allows pests to reach previously unreachable areas. Invasive tree bugs and blights have been on the rise in the United States. Dutch elm diseases, which is spread by the voracious and destructive elm bark bugle, are threatening hundreds of thousands of elms. The white walnut has been infected by butternut canker disease. Beech bark and beech-leaf disease are causing beeches to become ill. The emerald-ash borer, an iridescent green insect, has decimated ash trees. Sudden oak death is a pathogen that threatens oak trees. The woolly adelgid is also affecting hemlocks. The US cannot afford to lose its trees. By photosynthesis, the nation's existing forests absorb 9 per cent of its carbon emissions. The carbon dioxide in wood slowly releases into the atmosphere when trees die. Only 15 non-native pests, such as the woolly adelgid threaten to decimate up to 40% of these forests. Already, the annual emissions from biomass that is lost to invasives are comparable to those produced by wildfires. This carbon equivalent to the tailpipe emissions of 5 million cars each year. Natural solutions to climate change using landscapes to sequester CO2 are becoming more popular. The United States is not the only country investing millions in planting trees. Members of Congress in the USA want to plant 100 million new trees. However, they don't take into account exotic species. It is not certain that the new trees or existing trees will be able withstand the growing tide of invasive insects. Our Hail Mary climate solution could become part of the problem if the climate change pressures force nations trees to emit carbon dioxide instead of sequestering the gas.

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