Is the Use of Regionally Sourced Plant Material a Valid Requirement for Plants in a Climate Change Scenario?

Here in Maryland, as in many states, the assembly of a restoration planting plan often requires the explicit statement: "All plant material is to be sourced from (name physiographic province of the state) region of (name a term that describes five states including yours)."  The idea, and it is a noble one, is to ensure that the New York Finger Lakes wetland you are building is populated by plant material that was not sourced from Washington state, which could cause a dilution of high quality genetics from the regionally appropriate plants.   One of the first (academic or regulatory) problems of this rule is that it is only applied to live plant material, and not to conservation seed mixes, even though those seed mixes contain seeds for perennial native plants.  Oops.

But there's a much larger problem with focusing on New York-bred plants for New York projects.  Take a look below.

The vast majority of the country should experience a 5 to 7 degree increase in mean temperature.  Now, mean temperatures are deceiving because it's actually the minimum temperatures that impact things like growing seasons, insect overwintering mortality, and seed viability.  But let's ignore that, or, rather than ignoring it, let's take a look at the USDA growing season map, which is dictated by lowest temperatures, not mean temperatures.

You gardeners may recall that just a year ago, USDA revised its plant zone map based upon climate change data that is already rolling in.   How might a 5 degree change in the next 40 years impact this map further?  Well, let's look at Maryland, largely a Zone 7a state (0-5 degrees - we haven't seen temperatures that low in a decade).  An increase of 5 to 7 degrees could place Maryland in Zone 8a, a solid subtropical coastal growing zone.   That's a lot of change in a short amount of time.  Maryland ecosystems could quite feasibly start acting like South Carolina ecosystems.  Which brings us back to the topic of regional plant genetics.

If I'm planting an emergent wetland where even perennial plants will succumb after less than 10 years, it seems to make great sense to utilize the most locally native plant genetics possible.  But what about planting an oak swamp?  An alder thicket?  An upland hickory forest stand?  What about plants that quite conceivably could still be alive as the climate changes drastically over the next 40 years?  

For long-lived plants used in forestry and restoration work, I propose abandoning the "regional plant genetics" preferences and requirements, and instead, for us to begin looking to our south to find strong genetics for plants that are tolerant of the stresses that climate change is likely to bring us - increased flooding, increased drought, unpredictability of precipitation, and warmer minimum temperatures.   In Maryland, for example, the Shumard Red Oak exists in the wild in our southernmost county.  Yet, it's never mentioned in conversations about forestry, forest habitat management, or habitat restoration because "It's Not Native."  I think this is foolish, and currently there are 200 Shumard acorns from northern North Carolina now hardening in my basement refrigerator, to be used on habitat restoration sites.

"This is preposterous!" you might say.  An alternate example with a different story ending is the Sugar Maple.  Most foresters and landscape architects stopped planting sugar maples in the Mid-Atlantic in the early 2000s because the summer droughts were killing huge numbers of trees.   Yet, our DNR Forestry Division still refers to Sugar Maple as a "Maryland Native Tree" - providing it to citizens to plant on their property!

Here's what's going on with the Sugar Maple:

The species is predicted to lose over 90% of its range.  It's already happening.  Why - as a professional community - can't we agree to change and accept new conditions around us?

So when you're considering a list of long-lived trees for a forestry, landscaping, or habitat restoration site, there's no need to stick to "the standards" for native plants in your area.   Please plan ahead, and perhaps your innovation to prepare habitat for climate change will be noted as part of your legacy.   It's certainly better than being known as "the idiot who planted all these dead sugar maples 40 years ago."