Sunday, December 1, 2013

Where they headin'?

Recently, a study by US Forest Service Researcher Christopher W. Woodall reported that 70% of 'northern' tree species are regenerating significantly further north and/or at higher elevations than their mean biomasses (where most of the mature trees of that species historically grow).  If the current trend stands, many northern tree species' biomass may migrate up to 62-miles (100-kilometers) over the next century.  Other species' range appear to be decreasing all together, though they may be thriving in Canada since this study only sampled trees in the United States.  While northern tree species are retreating northward, southern species are having greater seedling success at higher latitudes, and some signs show that some southern species may begin invading even more southern latitudes.

Bob Dylan said 'the times they are a-changin,' and many researchers would agree.  Now we can debate whether climate change is real, and whether its causes are natural or man made, but for the sake of argument let's agree something is happening with our climate.  Our question is 'what about our urban and landscape trees?'  The affects of climate change on tree species may be somewhat predictable.  Decline diseases on sensitive tree species may become more pronounced, thus shrinking the area suitable for them to grow.  While other, more adaptable, species may thrive in greater ranges.

We can look at this as both a challenge and an opportunity.  The challenge will come from trying to preserve some well-loved and traditionally planted landscape species.  Pest and disease ranges will likely change as well, and so our management strategies will need to adapt.  But in some instances, there will be opportunities to introduce and diversify our landscapes with new plant species/varieties.  I know I wouldn't mind having some nice flowering oleander (Nerium oleander) in my, for now, zone 7 garden.

Check out your hardiness zone.