Seeking sunlight: How loss of light damages woodlands
The phone lit up after last month's column on darkness. Lots of readers contacted me to say that they value dark, starry skies. Many feel a great loss as dark skies are nearly a thing of the past.
Today, though, I'd like to turn from darkness to light. As in, sunlight, and its importance in ecology.
Natural sunlight is as critical as natural darkness. A no-brainer? Not necessarily. There's a serious lack of sunlight in our natural areas, and a lot of people aren't aware of the problem. The loss of light is one of the many interconnected causes of the decline in native woods and prairie.
"Wait a minute," you might be thinking. "The sun shines pretty much every day, even behind clouds. You plant native plants, let the sun shine, and it's all good, right?"
If only it were that easy.
The sun indeed shines, but sunlight doesn't always get where it needs to be.
Some background: Prairies and woodlands are sun-loving places. Prairies need the full blast of the sun, all day, every day. Coneflowers and compass plants cry, "Bring it on!" in the full summer sun. Indian grass and buffalo grass, prairie pollinators and predators all flourish when bathed in sunlight.
Woodlands require sunlight, too. Oak seedlings and young hickory trees must have sun, or they won't survive. Spring violets, summer lobelias, and fall asters need the dappled sunlight that filters through the canopy of oak trees.
For thousands of years, our natural areas were filled with sunlight. One reason they remained open and light was fire. Fast-moving fires raged across prairies, preventing trees from growing on the expansive grasslands. The herbaceous prairie plants remained unscathed because the majority of their biomass, or living material, exists underground. They are, in fact, rejuvenated by fire. For centuries, regular fires allowed the sun to shine unimpeded on the prairie.
Woodlands also evolved with fire, and therefore with sunlight. The relatively thick bark of oak and hickory trees is resistant to fire. Young trees are able to re-sprout from the ground if damaged. They spend a lot of energy growing deep in the ground, so they are well-established and resistant to surface flames. Centuries of fire kept other plant species in check. Thin-barked, shade-producing maple and basswood trees couldn't survive fires. These native species grew in protected pockets on the lee side of rivers and streams, while oak-hickory woodlands grew strong in areas prone to fire.
Enter invasive species. Thousands of kinds of plants and animals have moved across continents and oceans in the last two centuries, thanks to the increasing mobility of people. Some newcomers have had little impact on native ecosystems, while some have been devastating.
Two notorious game-changers in our landscape are honeysuckle and buckthorn. Think of these as sunscreen with SPF 50-plus-plus in oak woodlands. They grow thickly and quickly, producing multiple stems with lots of leaves. They leaf out early and hold leaves long into the fall. They transform an open, light woodland into a densely shaded thicket.
An invasive, shade-producing woody plant that takes hold in fields rather than woods is autumn olive. Like its woodland counterparts, this invasive shrub is tenacious, fast-growing, and formidable. It blocks sunlight, takes up space, and spreads rapidly across fields. It's the bane of many prairie restoration areas.
No fire, no sunlight. No sunlight, no oak seedlings. No oaks, no acorns. No acorns, fewer wildlife that depend on acorns. There is a cascading effect in woodlands, and in prairies as well.
Sunlight isn't the only ticket to success in native ecosystems, and shade is by no means the only influence of invasive species. But seeking sunlight is a worthwhile pursuit in restoring health to natural areas. When people ask me why the forest preserve district sets fire to nature areas, one answer is "sunlight." If people wonder why we cut trees in a forest preserve, the short answer is also "sunlight." We are, in a sense, guided by the light.
In today's landscape, fire isn't always possible. The size and shape of the landscape is vastly different from how it was 200 years ago, the fuel (in the form of native plant litter) is often absent, and the vagaries of weather come to play. To help keep shade-producing vegetation at bay, restoration often requires manual thinning of shrubs and trees. And it's a big job.
Outside my office window, the snow-covered prairie glistens in the winter sunlight. Tonight, it will sparkle in the light of the moon. Let there be light, and let there be dark - a good practice for living in the natural world.
•Valerie Blaine is a naturalist with the Forest Preserve District of Kane County. You may reach her at blainevalerie@kaneforest.com
How you can help bring light to the woods
You can help bring light to the woods this winter. There are lots of opportunities to chip in with brush clearing, invasive species removal and opening up the woods and prairies. Here are just a few restoration activities coming your way:
Thursday, Jan. 21: 9-11 a.m., Johnson's Mound Forest Preserve
Saturday, Jan. 23: 9 a.m. - noon, Fabyan Forest Preserve (East)
Saturday, Jan. 23: 9 a.m. - noon, Glenwood Park
Saturday, Jan. 23: 9 a.m. - noon, Bliss Woods
Saturday, Feb. 13: 9 to 10:30 a.m., LeRoy Oakes Forest Preserve
These are wonderful family experiences that are good for all ages. We recommend dressing in layers, wearing boots or heavy duty shoes and gloves. Please arrive 5-10 minutes prior to workday start time, and be sure to sign in with the workday leader (volunteer site steward). For directions and details, call (630) 762-2741 or visit <a href="http://www.kaneforest.com">www.kaneforest.com</a>.
- Valerie Blaine