Tuesday, March 27, 2012

What an Odd Spring

Dry pool in Stoneham, MA, 26 March, 2012
2012 is turning out to be one of the strangest springs that a lot of us can remember.  In early March the first reports of salamander and frog migrations in Massachusetts started trickling in.  Before the end of March, Massachusetts vernal pool observers were reporting chorusing American toads, Gray Treefrogs, and Leopard frogs – three to four weeks early!  There were even Green frogs calling just to the south in Connecticut.  To boot, the water levels in many vernal pools around eastern Massachusetts seem to be extremely low – many have even been observed dry already.

The fact that spring is happening so early has generated a lot of discussion about what we're observing, and what effects there may be on the ecology of vernal pools in the northeast.  Are we observing a major shift, or an extreme swing within the range of “normal variation” this year?  Will the long-term patterns of rain and snow change enough to affect vernal pool ecology?  What will happen to the salamanders and frogs that usually breed in my pool if it's dry this year?

Vernal pool organisms are adapted to significant variation year to year.  They "expect" boom and bust years, in as much as their life cycles are adapted to tolerate quite a bit of annual variation.  For spotted salamanders and other long-lived amphibians, a very dry year is no big problem to a population; many will sit out the year, and they will just try again next year.  Populations of shorter-lived animals (wood frogs, for example) might wink out in pools that are affected in a year like this, but tend to get around the landscape pretty well, and so can easily recolonize pools after a string of bad years has wiped out a breeding population.

The really low water and early breeding that we're seeing this year is bizarre and a little disquieting to some folks that watch the early spring amphibian phenomenon.  But are we seeing the beginning of major change in the environment?  Data show that the climate is trending toward warmer conditions (not saying anything about why - that's a topic for a different blog).  The Blue Hills Observatory in Milton, Massachusetts (http://www.bluehill.org/has data that show we're also getting wetter here in Massachusetts.  However, the curious thing about these observations is not necessarily the amount of water, but when it comes.  Though anecdotal, winter and spring seem drier than usual, and we seem to get dumped on in late spring and early summer - too late to be of much use to early spring pool breeding amphibians.  That's a pattern to start paying close attention to, because it could have real implications for vernal pools.

We won't really know for a long time if the strange spring of 2012 is just a "bust" year or if it portends real changes in the environment that will affect vernal pool ecology.  For the time-being, we're kind of left to wonder, and hope that we still get to see some salamander congressing.

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