NIMBY? Heggie’s Rock!

NIMBY: Not In My Back Yard.  

This phrase is usually used to discourage the location of something undesirable in one’s neighborhood.  But in my case, I’m using it to remind myself that, yes indeed, sometimes the most interesting and desirable places are hidden in my own backyard.  I found this to be true of my recent exploration of Heggie’s Rock, not far from my Aiken, SC backyard. 

Named for Archibald Heggie, a Scot who acquired the land in the early 1800s, Heggie’s Rock Preserve  is now owned by the Nature Conservancy and is designated as a National Natural Landmark. This exposed granite outcrop covers some 130 acres and is a stunning example of how life survives in the harshest of conditions.  Facing periods of drought and oven-like temperatures, lichens and mosses eke out a living on the bare rock, which harbors rare plants and even a species of midge only found here. Beauty resides here too, especially in the vernal pools, called solution pits by those scientifically-inclined although I prefer the term “dish gardens.”

Yet as unusual and beautiful as this area is, few know about it and fewer still get to explore it.  And that is by design. This is a fragile ecosystem, one easily damaged by human activities.  All you need to do is check out the graffiti on the rocks at Forty Acre Rock to see what I mean.  Closed off to casual visitors, the only way to visit this extraordinary place is by taking a tour with a trained docent.*

So when I got an invitation from esteemed geologist Walt Kabilius to join Ruth Mead’s class of Master Naturalists that he would be guiding through Heggie’s Rock, I jumped at the chance.  And just by chance, the torrential rains of the day before had cleared the sky, leaving conditions perfect for our exploration.

Half of our day would be spent gaining insight about the geology of the area from Walt; the other half would be lessons in lichens, led by Malcolm Hodges, a biologist, zoologist, ornithologist, and lichenologist extraordinaire.

I was nerding out.

It all starts with the rocks, so before setting foot on Heggie’s Rock, Walt took us back to Geology 101 with a description of how this granite outcropping came to be. A bubble of magma rose through the crust and slowly solidified in the crust. This “pluton” of igneous rock containing quartz, potassium feldspar, and plagioclase feldspar gradually became unearthed due to erosion, creating this dome of granite exposed on the surface.

Walking out on the rock, we saw the dish gardens which were filled with water from yesterday’s storm.  Formed by the corrosive effects of acidic water, both from rain and leached from lichens, these shallow pools collect a thin layer of sediments that allow plants such as elf orpine, Diamorpha smallii, to take root. This tiny succulent member of the stonecrop family makes its own sunscreen with anthocyanins turning it a bright red, protecting it from sun damage by absorbing blue-green and ultraviolet light.

• 

• 

• 

• 

• 

In pools a little deeper, we saw the threatened Gratiola amphiantha, otherwise known as pool sprite or (my favorite) snorklewort.  You gotta love a plant with a name like that! This plant is found mostly in Georgia, although some are in Alabama and South Carolina. Snorklewort sends a long stem from the basal rosette growing in the sediments, from which two leave form that float on the surface and hold a tiny flower in the air so that it can be pollinated by insects.

Mat-forming quillwort is unpretentious.  It doesn’t attract the eye with bold color like the elf orpine.  It doesn’t even have a weird name like snorklewort. But it does have the singular characteristic of being a truly endangered species protected under the Endangered Species Act. Isoetes tegetiformans was first described in 1978 from a specimen collected at Heggie’s Rock. There are only four remaining populations, all on granite outcrops, all in Georgia, and all on private property.  Related to club moss, this aquatic plant is threatened by habitat loss due to granite quarrying as well as by damage by hikers or off-road vehicles. Here’s a fun fact: According to one source, Georgia is the world’s largest granite producer. (And despite being called the Peach State, South Carolina actually produces more peaches.  Just saying.)

Malcolm Hodges points out the endangered mat-forming quillwort

Yet another rare plant is Puck’s orpine, Sedum pusillum.  Very similar to elf orpine, this sedum grows in drier parts of the granite outcrop under shade.  Only found in North Carolina, South Carolina, Alabama, and Georgia, this is a Federal Species of Concern.  Our group carefully tiptoed around these plants as we made our way across the rock.

Mosses were abundant on this rock outcrop.  Malcolm lifted up a large swath of moss, showing us how it lay on top of the rock like a rug.  Since it was spongy from the rain of the night before, it was unhurt by his stepping on it.

Walt pointed out some “hard” features about the rock under our feet.  He showed us xenoliths, rocks that became embedded in the magma while the magma was cooling. How gneiss!  He had us go on a dike hunt, explaining how a crack in the solidifying granite became filled with crystalized magma forming a narrow band of feldspar.  And Walt showed us the rim of cloudy rock at the edges of rain water streaming off the rock.  Amazingly, this is opal, formed by acidic weathering of the rock as rain water carried silica down the rock.   (I hope I got these facts straight—please don’t take my scant knowledge of geology for granite.)

• 

• 

Here’s another fun fact: this granite pluton is undergoing sheet exfoliation, also called onion skin weathering. One explanation for this is that rocks formed at great pressure, when brought to the surface, begin to slough off the outer layers as they expand slightly.  As our lichenologist guide Malcolm Hodges explained, this sheet stays a bit cooler than the surrounding rock, allowing peppered rock shield lichen, Xanthoparmelia conspersa, to proliferate.

Malcolm took us through the four major categories of lichen: crustose (thin like a crust), foliose (think foliage—leaves), fruticose (branchy like a fruit tree), and a new one for me, squamulose (small, often overlapping scales). Although I’d always liked the story of Amy Algae and Freddy Fungi taking a “lichen” to each other in a symbiotic relationship with the algae producing food through photosynthesis and the fungi providing the structure, Malcolm had a darker story.  In his alternate version, the fungi subjugates the algae, enslaving it to produce food.  As I peered through a strong hand lens, I could indeed see the dark threads of fungi spreading out over the algae.  And yet, a quick Internet search referred only to a symbiotic relationship.  So I’m not changing my story.

It was impossible to walk across Heggie’s Rock without stepping on lichens.  Practically the entire surface was black with tiny Piedmont cobblestone lichen, Acarospora piedmontensis, obviously a crustose variety.

Mounds of the common reindeer moss lichen covered large areas of the rock.  Although I was familiar with reindeer moss, I didn’t realize that there are two different species: Grey reindeer moss and the greener Southern reindeer moss. Mixed in with these lichens was the British soldier lichen, with the red tops producing spores but not carrying alga so they are unable to reproduce.  These lichens spread as pieces break off and are carried to a new location.  Bushy beard lichen with its wispy strands grew on an old twig. With their branchy structure, it’s easy to group all these as fruticose lichen.

• 

• 

• 

Usually growing on tree bark, ruffle lichens have black hairs called cilia along the edges of their uplifted lobes but are often hard to tell apart. Malcolm used chemical testing to identify a ruffle lichen as a Perforated ruffle.  With its leaf-like lobes, it belongs with the foliose tribe.

A squamulose lichen, rock olive indeed had the shape and color of an olive.  So many lichens—I’m really lichen it.  Note to self, though: Don’t use lichen puns with a lichenologist.  He’s heard them ad nauseam and will not be pleased.  And if you want to learn more about lichens, go to the lichen portal at georgiabiodiversity.org .  You’ll find Malcolm Hodges’ name on just about every page!

Thanks to Ruth Mead, a Master of all Master Naturalists, for getting Walt and Malcolm out on Heggie’s Rock, we couldn’t have had more informative and interesting guides as we learned about this unusual area. And to think that this is tucked away not so very far from home!  Who knows what other natural wonders are waiting to be discovered, yes indeed, right here in our own backyards.

*Since Heggie’s Rock is closed to the casual visitor to protect this fragile ecosystem, contact: 404-873-6946 or tncgeorgia@tnc.org to make arrangements to see it.