Charleston Area Lost More Than 10,000 Acres of Tree Cover Since 1992, Making Floods Worse

Turbocharged by a warming climate, rain bombs and rising seas swamped the South Carolina Lowcountry this year, sending murky floodwaters into streets, businesses and homes.

At the same time, developers continue to transform forests and wetlands into even more homes and shopping centers — destroying acres and acres of spongy land that could help sop up these rising waters.

A new analysis requested by The Post and Courier for the Rising Waters project shows how the Charleston area’s unprecedented building boom made us more vulnerable amid the accelerating forces of climate change.

Researchers at the College of Charleston’s Lowcountry Hazards Center used advanced satellite and aerial imagery to measure changes in the area’s tree canopy — a key measure of the land’s ability to naturally manage flooding rains.

What emerged is among the most nuanced looks yet at how our land has changed in recent decades, a powerful new tool for residents and planners alike.

Here’s what they found:

• Charleston County lost about 10,800 acres of tree cover since 1992, an area larger than the Charleston peninsula and Daniel Island combined.
• Some areas lost more than others. A booming city of Charleston lost 5 percent of its tree canopy. North Charleston saw a 4 percent drop.
• Mount Pleasant, the region’s growth leader, lost 22 percent of its tree cover.
• Other tree-loss hot spots include West Ashley neighborhoods off Bees Ferry Road and the Glenn McConnell Parkway and North Charleston neighborhoods downstream from the Palmetto Commerce Parkway.

• A few places had more tree cover, especially older subdivisions on James Island. But these urban forests shade sidewalks, driveways and roofs — hard surfaces that funnel stormwater into ditches and drains. They don’t make up for the loss of natural forests and wetlands.

“The big takeaway is that you’re seeing more water run off the surface that used to be going into the ground and pumped into the trees,” said Norman Levine, director of the Lowcountry Hazards Center.

The Charleston metro area’s shrinking tree canopy is part of a national crisis. In 2018, the U.S. Forest Service estimated that American cities were losing 36 million trees a year, a massive reduction in greenery that makes cities hotter and less healthy.

And in coastal South Carolina, tree losses are happening when we need these natural stormwater pumps more than ever. A rapidly warming planet fuels heavier rains and higher tides. This year to date, we’ve had 64 tidal flooding events, the second-most on record. Monday morning’s expected 7.5-foot high tide could increase this tally, flooding low spots during the height of rush hour.

The new Lowcountry Hazards Center analysis also helps explain a surge in anger among flood-weary property owners. They say their elected leaders and planning commissions failed them. They’re furious about storms that forced them from their homes in North Charleston’s Pepperhill area, how floods sent stormwater coursing into living rooms of Central Park Road on James Island — even prompted a pastor in West Ashley to grab a kayak and paddle in his flooded church.

But the study’s findings also point toward solutions, ones that would simultaneously preserve the Lowcountry’s beauty and strengthen our ability to take a storm’s punch.

To view an interactive map showing changes in tree canopy cover in Charleston County since 1992, click here. Data provided by the College of Charleston's Lowcountry Hazards Center.

Nature’s Umbrellas

On April 23, clouds built over Charleston, darkening the massive live oaks in Cannon Park. The rain fell that afternoon, and the trees acted like umbrellas at first, catching and holding raindrops in their giant limbs. Then the rain picked up. Water pooled on Ashley Avenue by the Medical University of South Carolina. Within an hour, thigh-deep water surrounded parts of the medical district. Nearly 6 inches fell by nightfall.

Trees are impressive water pumps and air conditioners. A mature tree can soak up 40,000 gallons a year. They pump water through their roots, allowing more water from the ground to seep in. Then they release this moisture in their canopies like misting humidifiers, cooling everything around them.

The Lowcountry has its gorgeous live oaks, with their great elephantine limbs. It has stout pecan trees, pines and cypresses — a canopy that covers about 44 percent of Charleston County, the Lowcountry Hazards Center analysis shows. That compares with 47 percent for Charlotte, a city known for its lush tree canopy.