Rapid Rise of Emerging Diseases Threatens Northern Hemisphere Trees

Photo Credit

Andrew Gougherty

Powdery mildew on maple leaves in Vancouver, BC, CAN. 

Emerging tree diseases not only weaken trees but can also lead to increased tree death and, in some cases, the extinction of local tree populations. While not all diseases are instant killers, they can have profound and far-reaching effects on tree communities by disrupting the ecosystems they inhabit. Scientists are working to identify the areas where new diseases are showing up and spreading most rapidly and to understand which trees are most vulnerable to these emerging threats. This knowledge is crucial for identifying regions where new tree disease threats could arise in the future.

Key Findings 

• Over the past two decades, the number of newly emerged tree diseases has surged, doubling approximately every 11 years around the globe. 
• New diseases may affect trees both in their native habitats and new places where they have become established. 
• Pine trees have been hit hardest by new diseases, followed by oaks, eucalyptus, and walnuts.
• This research reveals emerging diseases are unevenly distributed in different regions of the world and on various kinds of tree. This information can help scientists predict future tree disease threats.

Photo Credit

Andrew Gougherty

Figure: a) Geographic distribution and (b) temporal accumulation of 962 first reports of emerging tree diseases since 2000 for 24 tree genera.

Approach

Scientists conducted in-depth research to analyze the speed at which new tree diseases are emerging worldwide. They compiled a substantial dataset of new tree disease reports published over the past two decades. The study also delved into how the number of these reports has evolved over time.

The findings are striking. Reports of new tree diseases are accumulating at an alarming rate on a global scale, with the number of such reports doubling approximately every 11 years. Among the tree genera examined, pines are bearing the brunt of this surge in new diseases, followed by oaks, eucalyptus, and walnuts. The scientists think that these four tree genera are being affected most strongly because they are widely distributed geographically, they are extensively used in forestry and agriculture, and they have been transplanted outside their native regions.

This research highlights the swift emergence of new diseases and underscores that tree diseases are unequally distributed across different regions of the world and among various tree species. 

Outcomes

• Insight gained from this research serves as an essential first step toward developing statistical models that can map and predict the occurrence of emerging tree diseases. 
• Study findings further emphasize the urgency of monitoring and addressing this critical issue especially considering that climate change, changes in land use, and global trade can facilitate the emergence of new tree diseases.