Of course, it is old but that can't explain why younger trees are dying as well. Here in front of the pond, remain the stumps of two substantial trees that have been removed.
There is evidence of widespread ozone damage to vegetation in Europe. Ambient levels of ozone cause visible leaf damage, reduce crop yield, affect crop quality and reduce the biomass of sensitive plant species.
Ozone critical levels for vegetation are regularly exceeded across Europe.
Ozone-induced yield losses for 23 crops (mainly arable) in 47 countries in Europe were estimated to be €6.7 billion per year for year 2000 ozone concentrations.
Evidence suggests that ozone and nitrogen can have both synergistic and antagonistic effects on species and ecosystem processes; they may interact in unpredictable ways to affect plant communities.
Thus, the foliar Hg concentrations in vegetation at the contaminated site were up to 3 times more (for Acer sp.), 8 times more (for Rubus sp.), and 17 time more (for fern) than those in plants at the uncontaminated site.
from this paper, which happens to be mostly about soil, not trees.
"The Ohio Valley has attracted lots of large industrial facilities that put huge levels of toxic and other pollutants out that are known to impact development," Blair said.
Foremost among those is mercury, a powerful neurotoxin and one of the most-studied and best understood of the 80,000 industrial chemicals the U.S. Environmental Protection Agency (EPA) allows into the air, water and land every day." Of which only about 200 have been required to be tested.