Mason Heberling

Deer don’t just eat your garden, they eat native wildflowers too. That in of itself is not a problem.  After all, white tailed deer (Odocoileus virginianus) are native to Pennsylvania.  Deer in PA were once hunted to local extinction, having to be reintroduced.  But deer are now well beyond historic densities.  There are many reasons for this, including land use change (deer do well in forest margins resulting from forest fragmentation), absence of major predators (like the mountain lion, which is now extinct in PA), abundant food sources (like your garden and farms), and hunting management practices.  Deer management is a controversial topic, both for ethical reasons and for competing interests (e.g., managing deer herds for trophy hunting vs. maintaining historic levels for forest management).  The high densities of deer in PA has many consequences ranging from public health (disease carriers esp. tick-borne diseases), car accidents that result in human injury (and higher in car insurance rates), as well as the many ecological consequences (declines in native wildflowers, changes in forest tree composition and forest regeneration, and facilitation of non-native, invasive plants, to name a few).
 
But how do we really know the effects of deer overabundance?  Some impacts are quick, but many others result from chronic deer overabundance.  Long term deer exclosures provide one method to study the effects of deer on the landscape (monitoring fenced forest plots paired with unfenced plots).  These studies are important, but require maintenance and few date to more than a few decades.
 
A recent study introduced a method to measure the effects of deer overabundance using herbarium specimens in Quebec (Canada).  Marie-Pierre Beauvais and others paired historic herbarium specimens (dating back to 1848!) of the large flowered, white trillium (Trillium grandiflorum) with recent observations to find that plants in sites today (with deer) have significantly smaller leaves than those of herbarium specimens.

Read the abstract of the study here:  http://www.nrcresearchpress.com/doi/abs/10.1139/cjb-2016-0206#.WwLeZakh3OQ
 
This study shows the potential of herbaria as time capsules to understand the direct and indirect effects of human activities on our environment.  There is so much knowledge in these specimens waiting to provide insights into the Anthropocene.
 
The specimen of White trillium (Trillium grandiflorum) below (left) was collected on May 21, 1908 by Carnegie Museum of Natural History Botany curator Otto Jennings in Washington County, PA. 
 
Note the specimen on the left, collected in 2005.  I admit this particular comparison only shows two specimens at two time points (too small a sample size to be meaningful on its own) and is cherry picked, but I show these just to illustrate the immense potential to measure hypothesized changes in our plants as a result of human induced environmental changes.  I hope someday to follow up on the cool 2017 study by Beauvais and others using specimens to study changes in the flora western Pennsylvania as a result of historic and recent changes in our deer populations. 

Collected on March 3, 1992, this specimen was found in Franklin Township, Ohio (Adams County) by Allison Cusick.  Although not at the time of collection, this site is now protected for conservation.  Allison was a state botanist for Ohio and currently, an active Research Associate at the museum.  He has collected more than 4,800 specimens (and counting) for the Carnegie Museum’s herbarium!
 
A rare species of conservation concern, Trillium nivale (snow trillium) grows less than 4 inches tall and is the smallest of the Trilliums.  Found in rich forest understories, it is one of the earliest spring flowers to bloom in our region, sometimes even while snow is still on the ground!  Spring will arrive soon, although this year it seems it already arrived...