Bee and bat populations alike experience a sharp decline in North America. Whereas, however, the dying of bees remains a bit of a mystery, the cause of the collapse of bat populations has been given a name: It is a fungitic disease labeled WNS, White Nose Syndrome, that has infected and killed an estimated 5 to 7 million individuals so far and is still rampaging, from North Carolina to Tennessee up to Quebec, through 16 US states and four Canadian provinces.
The fungus geomyces destructans' growth is restricted to low temperatures and seems to find ideal conditions for reproduction in hibernating bats. Specimen of nine bat species have been identified with the disease so far, including the already endangered Indiana bat and the more common little brown myotis (There are 45 bat species in North America, 25 of which hibernate in caves and so very likely are susceptible to the disease). When the first cases were detected in a NY cave near Albany in 2006, the disease was likened to CCD, Colony Collapse Disorder in bees, and scientists assumed that different factors such as exposure to pesticides, stress, parasites and others also characterizing CCD could be responsible for the rapidly climbing mortality rates in the afflicted regions. The later comparison, though, to chytridiomycosis, an infectious disease that has led to a large-scale decline of amphibians worldwide, seems more accurate, since in both cases a fungus appears to be the causative agent of the disease.
Bats suffering from WNS all show the same symptoms: their muscle tissues, wings and, most conspicuously, their noses are covered with white fungal growth. It seems that the fungus, though not air-borne and presumably transmitted by physical contact alone, can easily survive in the soil and also on human clothing and so be unintentionally carried from cave to cave; the spread so far was probably also caused by human activities.
Very much like bee's Colony Collapse Disorder, WNS has caught the attention of a wider public primarily because, just like bees, bats are also vital for the agricultural industry and so their decimation and possible extinction would and already does have a great economic impact: in the tropics, they are important pollinators; in North America, they are essential for pest control, consuming many thousands of metric tons of insects each year. According to an article published in Science (sciencemag.org March 13, 2011), the estimated average value of bats to the North American economy is 22.9 billion dollars a year. A large-scale loss of bat populations (Adding to the problem of WNS, many thousand bats a year belonging to species that are not cave- but migrating tree-dwellers die from wind turbines) would lead to a further intensification in the use of pesticides: maybe an additional financial burden to agriculturalists, but the real costs caused by the so-called "downstream effects" of increased pesticide use can not even be calculated and damage, especially long-term ecological impact, might be immense.
Spores of geomyces destructans have also been identified in Europe but have not caused epidemic diseases in any of the local populations so far. Possibly, the fungus even originates in Europe and European species are immune to it. It is also still not 100% clear whether geomyces destructans is not only an opportunistic pathogen and a yet unknown virus or bacteria lies at the core of the widespread dying-off of North American bats, which would be one possible explanation why the European populations have so far gone unaffected.