Powdery mildew on maple in Vancouver, Canada. Trees around the world are being battered by a surge in new diseases - with Europe on the front line, biologists have warned. PHOTO BY ANDREW V.GOUGHERTY/SWNS
Trees around the world are being battered by a surge in new diseases – with Europe on the front line, biologists have warned.
Disease is a major cause of tree death both in the wild and more urban areas with new strains affecting species that have no resistance.
A study by the USDA Forest Service which looks after all the forests in the US and published in the journal NeoBiota, has highlighted the problem.
Dr. Andrew Gougherty a research landscape ecologist at USDA said: “The continued emergence and accumulation of new diseases increases the likelihood of a particularly detrimental one emerging, and harming host tree populations.”
Already we have had ash dieback in Europe, as well as chestnut blight, which has effectively eliminated chestnut in its native range in the Appalachian Mountains.
There is also sudden oak death in California and butternut canker in the eastern US, all of which could eliminate species.
When exposed to novel hosts, emerging diseases can cause mortality previously unseen in the native range.
The study looks at where tree diseases have accumulated fastest, and which trees are most impacted by new diseases.
This information could help researchers and land managers better predict where new diseases may be most likely to emerge.
The team analyzed more than 900 new disease reports on 284 tree species in 88 countries and quantified how emerging infectious diseases have accumulated geographically and on different hosts.
Dr. Gougherty said: “The ‘big data’ approach used in this study helps to characterise the growing threat posed by emergent infectious diseases and how this threat is unequally distributed regionally and by host species.
“The accumulation (of new diseases) is apparent both where tree species are native and where they are not native, and the number of new disease emergences globally were found to double roughly every 11 years.”
Among the trees he assessed, pines accumulated the most new diseases, followed by oaks and eucalypts.
This is likely due to their wide native distribution in the Northern Hemisphere, and the planting of pine forests throughout the globe.
Europe, in aggregate, had the greatest total accumulation of new diseases, but North America and Asia were close behind.
In addition, he found more emerging tree diseases in areas where tree species were native versus non-native, with the exception of Latin America and the Caribbean, likely because most of the trees he assessed were not native to this region.
He added: “Unfortunately, there is little evidence of saturation in emergent tree disease accumulation.
“Global trends show little sign of slowing, suggesting the impact of newly emerged diseases is likely to continue to compound and threaten tree populations globally and into the future.
“Climate change is likely also playing a role, both by creating more favorable conditions for pathogens and by stressing host plants.”
Produced in association with SWNS Talker
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