"That leaves as the main suspects CO2 and climate change "

I will add a third reason that could be way more important than either of these.  Just think for a minute.  What is our biggest honey bee management problem?  Varroa mites and associated diseases.  We imported varroa mites.  A few posts back White Nose Syndrome in our native bats was mentioned.  We imported this fungal infection.  Where I live all the ash trees are now dead.  Not long ago ash was one of the main forest trees here.  They died because of emerald ash bore.  We imported the ash bores.  Citrus in Florida is in trouble due to an insect pest that transmits a bacteria deadly to citrus trees if I understand the sequence properly.  We imported the insect.  Then there are the imported fungi that destroyed the chestnut trees and the American elm trees that both used to be common and are now extinct in the wild.  Right now we have a new disease of our native beech trees.  It has killed some and all are obviously sickened.  It has been here about five years now and we still do not know if it is fungal, bacterial or viral.  All we know is it kills slowly, is highly contagious and suddenly showed up a few years back.  I am sure it is an import because nothing else makes sense.  Our local forests are called beech maple forests.  It will not be long before the beech part is dropped as most or all may be gone.  As pure stands of maples do much poorer than the beech maple mix will we have to drop the maple part also in 50 years?  Not to mention the fact that the maples also have a new unidentified disease.

We do not know much at all about fungal, bacterial or viral diseases of our native insects.  I have to wonder how many such diseases we have imported that are doing immense damage and we have no clue it is even happening?   Remember we have a miserably poor understanding of viral diseases of an important domestic insect, the honey bee.  Does anyone at all know anything about viral diseases of the monarch butterfly?  My gut feeling is such things are more likely to be the real issue than carbon dioxide or climate change.  It is pretty easy to realize when you have imported an insect.  It is a lot harder to realize you have imported a fungi or bacteria or virus.

Dick

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