California's Ailing Oaks: Sudden oak death has wiped out nearly a million oak trees in California in the last 20 years, The Times reports. Whole landscapes have been transformed, and even healthy trees are being cut down to stop the spread of the disease. Sudden oak death "spreads via water, including windblown rain, and transplanted soil. Its advance has been considered inexorable, and the discovery of [an] uninfected patch of forest was considered sheer good luck." Now, scientists are experimenting with injecting a special kind of fungicide into their lucky strand of trees to try to find a way to stop the hardwood horror.

Michigan's Ash Assassin: The state has reportedly lost millions of its native ash trees to an invasive pest known as the emerald ash borer. The statewide news site Mlive reported in June that the insect, which scientists suspect came from somewhere in Asia on "solid wood packing material carried in cargo ships or airplanes," first arrived in Detroit in 2002. Since then, "dead and dying trees line city streets, suburban backyards, golf courses and retail parking lots as one of the most popular landscape trees falls to the beetle and its larvae." The insects can be stopped using store-bought pesticides, but their infestation has taken a huge chunk of the state's ash tree population already.

The West's Waning Whitebark Pines: These high-elevation trees are endemic to the Western United States, in the Rocky and Sierra Nevada mountain ranges and all over and around Yellowstone National Park. They were recently rejected from the endangered species list, not because they're not in danger, but because the U.S. Fish and Wildlife Service doesn't have enough money to protect them right now. A warming climate has been blamed for the trees' demise, as the "once-cold temperatures of the trees' mountainous habitat formerly isolated them from the deadly mountain pine beetle (Dendroctonus ponderosae), a native species that prefers warmer climes. But rising temperatures have brought the beetle into Yellowstone National Park, where the bugs have killed as much as half of the park's whitebarks in the past 10 years," according to Scientific American. Other plagues, such as the invasive European white pine blister rust fungus, threaten those specimens that the beetles don't get.

Missouri River Massacre: This spring saw dramatic and deadly flooding all along the Missouri River. Those affected had an immediate challenge in trying to save themselves and their houses from the rising waters. But after the river crested, the floodwater stayed. Now, the trees whose roots it covers are in danger of dying off as the water chokes off their oxygen during their growth period. "Homeowners will lose such flood-intolerant tree species as spruces and crab apples, and even tougher species such as cottonwoods, box elders, American elms, silver maples and bur oaks will sustain damage after what will likely be months in standing water," The Bismark Tribune reported. Plus, floodwaters may carry any number of toxins that could change the chemical balance of the soil.