Foliage Spoilage & the Trees' Canopy Collapse
It would appear that there is a complex chaotic system in play that is resulting in the deforestation of the Earth.
Sampling Of Contributing Variables
It is difficult to list "types" of pollution that are causing the death of trees. For instance, what is acid rain? Is it air pollution or water pollution? And, there are some forms of pollution that have not yet been widely recognized, such as, thermal pollution. Instead of trying to define the type of pollution that is contributing to the mass mortality of the forests, why not just consider how "human output" is to blame? Drought
During the recent past there has been an unprecedented number of droughts and a measurable decline in the water table. Other severe weather including floods, winds, ice storms, etc. are also breaking records.
Insects and Worms
Some of the tree mortality might be from regularly occurring life cycles of critters like the gypsy moth caterpillar. However, the decline of the bee population and changes in the worm population appear to be a relatively new phenomenon. The is a serious pollination problem due to the devastation of bee colonies. The cause is not fully understood. Tree deaths due to the change in worms is thought to be a result of pH changes caused by acid rain.
Eurasian, as well as, other "foreign" plants and insects are taking over many species that evolved in the Americas. [e.g ailanthus (tree of heaven), Queen Anne's Lace, earthworms colonizing North Eastern forests, MALB (Asian ladybug beetles), bamboo, morning glory, the list of invasive plants goes on and on.]
In many of the destroyed trees a bizarre pattern can be observed. It almost appears as though a cannon has blasted holes through the leaves. Is it possible that a change in the Earth's atmosphere might be acting like a magnifying glass during certain times of the day? Perhaps in the early morning as the sun rises the light is hitting the trees in a new and different way?
Human activities are contributing to tree mortality and deforestation. Humans have also induced climate change in other ways. The combination of human induced climate change and human induced tree mortality are creating a cycle of exponential chain reactions. A better way to say it might be -- the veiled causes of the current tree deaths are an unanticipated result of human activities. This new form of deforestation contributes to more global warming. An increase in global warming and human induced climate change intensifies the rate of tree mortalities. The result could very well be "foliage spoilage and the trees' canopy collapse" in the very, very near future.