The Sunken Forest Tour: Change and Preservation

At this site, questions of change and preservation come together.

NPS/Sucena

If you had stood here in the summer of 2012 you would have been comfortably shaded by the towering body of a tall holly tree. Looking closely to brush before you and you may see its decaying trunk and skyward roots. The holly tree that once stood here came down during Superstorm Sandy in October of 2012. It’s collapse is a troubling sign. 

 

Tree’s falling in forests, of course, is not uncommon. In fact, trees collapsing due to illness or other factors is an important part of the natural life of forests. Decaying trees, branches and leaves enrich the soil of the forest, providing food for the plants which would grow up in its place. As trees fall they open up holes in the canopy overhead, allowing light to reach down to plants where it could not before. This allows young trees and saplings to grow in its place. 

 

The natural replacement of one tree with another is part of the process that fuels the succession we talked about before. In stable “climax communities” when an adult tree dies it is replaced by its own young. For reasons we outlined at our last stop this process is being interrupted. You may notice, for example, sapling Black Cherry trees growing in this holly’s place. Black cherries, though tasty to us, are not particularly popular with deer. Their leaves are packed with cyanide and likely to upset their stomachs when eaten. This results in what is called “selective grazing” where herbivores actively shape an ecosystem by eating some things and avoiding others. 

 

Black cherries, while native to this area, are common on Fire Island, thus the rare maritime holly forest is slowly being replaced by a more common habitat, representing a loss of global biodiversity.

 

But why did this tree fall in the first place? Recall when we discussed the rising water table, and thinning “vadose zone” while visiting the freshwater bog. Look below the boardwalk and you may see standing water beneath the holly tree’s roots. For many years this tree grew up in dry soil. By the time the tree collapsed, it’s soil was inundated with water which likely contributed to “root rot” and it’s eventual fall.

 

All around the Sunken Forest water is appearing in places where it did not before. Scientists in the park have been observing this phenomenon, monitoring the water table and testing it for salinity from sea water. It appears as though the water table on Fire Island is rising in concert with sea-level rise, one very troubling symptom of anthropogenic, or human-cause, climate change.