When a natural disaster isn’t a disaster

Humans often do more harm than good when we try to rebuild damaged landscapes

April 17, 2017
After a forest fire, the ecosystem can recover without human intervention. [Image credit: Glenn Euloth |CC BY-NC-ND 2.0]

Flames soared high above tree canopies and billowing smoke blocked the Northern California sun when a wildfire torched over 100,000 acres of the Klamath National Forest in 2014.

Two years earlier, Hurricane Sandy tore up the East Coast, throwing frothy ocean water high up the shore and stripping sand off hundreds of miles of beaches.

In the aftermath, humans did what we almost always do: We tried to return the forests and beaches to what they looked like before disaster struck. We let logging companies clear out tens of thousands of scorched trees and hired contractors to dump thousands of tons of sand onto bare shorelines, spending billions of dollars in the process.

But in doing so, we disrupt the natural recovery of those ecosystems, researchers suggest, citing a growing body of science on the unintended consequences of human intervention after natural disasters.

“In these heavily, naturally disturbed systems, humans are often thinking about cleaning things up,” says David Lindenmayer, an ecologist at the Australian National University. “But the process of making these systems neat and tidy can make them worse.”

He highlighted the problem in a January paper in Nature Ecology & Evolution. While most of the research on post-disaster ecosystem recovery has focused on the aftermath of forest fires, Lindenmayer says that many of the same issues arise when humans try to “fix” ecosystems after a wide range of natural events, from coastal storms to insect attacks.

“Plants and animals are very strongly adapted to dealing with natural disasters because that’s what they’ve evolved with,” says Lindenmayer. “You have a big fire or flood that comes through and the forest system restarts. If you drive machines all over it, to harvest the trees, the whole system’s natural recovery is completely screwed up.” In other words, a disruptive event that humans see as a disaster in need of intervention, may actually be an opportunity for healthy renewal — if we just stay out of it.

Lindenmayer works in forest ecosystems, and his research focuses on recovery after wildfires. He points to salvage logging — the common practice of removing burnt trees after a wildfire for commercial logging — as one strategy that hurts forests, even as it generates short-term profits for loggers and landowners like the U.S. Forest Service.

The burnt trees typically removed during salvage logging perform critical functions when left in place. They anchor the soil to prevent erosion, provide shade for newly sprouted trees and serve as homes for returning wildlife, says forest fire ecologist Dominick DellaSala, chief scientist of the Geos Institute in Oregon.

“I would say the most important ecosystem components are the dead trees,” DellaSala says bluntly.

And because salvage logging is almost always accompanied by artificial replanting of young trees — often placed much closer together than is natural — there is more wood available to burn, making wildfires more likely to occur sooner and burn more intensely than they would have otherwise, studies from burned Oregon forests showed.

“That system is very dense, and it’s prone to carrying the fires through the canopies of those young trees,” says Lindenmayer. “The severity of the fire is much greater, and the intensity is much greater.”

But Patricia Grantham, a forest supervisor at the Klamath National Forest who approved a plan for salvage logging after the 2014 fire, frames the process as removing fuel for future fires. “That will help us protect private property and homes in the future,” she says. And when wildfire inevitably returns, ridding the land of scorched trees can make the scene safer for firefighters. “Fighting fires underneath standing dead trees is a bad idea,” she says.

It also allows the U.S. Forest Service to gather some income by selling the rights to the burnt wood to timber companies, Grantham adds.

Having timber companies clear out the burned logs, she said, is far cheaper than having the government do the work itself. “I think that the estimate was that if we hadn’t sold those timber, and instead the government had said we’ll pay people to do this work, it would have cost millions of dollars,” she says.

Grantham asserts that money is not the main motivation for salvage logging. She noted that after the Klamath fire, she required helicopter logging, which is more expensive for timber companies and helps protect the ecosystem by keeping trucks from trampling the area.

But DellaSala, of the Geos Institute, says it’s all about money. “Economics is driving post-fire logging,” he says “Salvage is getting something of value from something that’s being degraded. But if that forest was killed in a fire, it wasn’t actually degraded.” Instead, he said, it’s renewing itself.

In beach ecosystems hit by storms, the financial incentives for human intervention are more obvious. Beaches erode naturally, but the process is at its starkest after large hurricanes like Sandy because they pull massive amounts of sand from the shore. In just a few hours, they drastically shrink the beaches that homeowners count on for property value and states need for tourism, says Joshua Kohn, a biologist at the University of California San Diego.

So state and local governments almost always try to rebuild beaches after big storms, by dragging new sand up to the shore in a process called beach replenishment. The projects are expensive, with a single nourishment costing on the order of millions of dollars.

Advocates of beach nourishment, like the American Society of Civil Engineers, cite benefits of well-maintained beaches, which serve as protective barriers for vulnerable shoreline structures and provide recreation for visitors and residents.

But the practice is harmful to the animals that live on and around beaches — dumping new sand on a beach smothers and crushes the tiny invertebrates who make up the foundation of the beach food chain. Their populations are significantly reduced following nourishment.

The type of sand that’s typically added to the beach worsens the problem, says Charles Peterson, who studies beach ecosystems at the University of North Carolina at Chapel Hill. Often, beaches are replenished with much coarser sand material that’s easier to get and more likely to stay put.

“The coarser the material you put on the beach the longer it may reside and stay on the beach without being eroded away,” he says. “But the coarser materials inhibit the recovery of the burrowing invertebrates that are so important for crabs, shorebirds and fishes.”

There are fewer shorebirds, for example, near heavily replenished beaches in North Carolina, according to a 2006 study.

Beach replenishment is not about helping the natural system recover, according to Peterson. Instead, it’s about helping people who live on the shore or visit it to enjoy the illusion of a functional beach for a few more years — until the next big storm comes. Artificial beach replenishment, Peterson argues, is really just a sand rental — it will eventually get pulled back into the sea.

But people will continue to try and hold their artificial line in the sand, he predicts. “Part of the hubris that we all have,” Peterson says, “ is that we can design nature to be to our taste.”

About the Author

Nicole Wetsman

Nicole Wetsman graduated from Bowdoin College with a major in neuroscience. Her work has also appeared at New Scientist, Stat News, Science Friday and others. Find her tweeting @NicoleWetsman, mostly about brains and women’s soccer.

You can follow Nicole on Twitter here.


Leave a Reply

Your email address will not be published. Required fields are marked *


The Scienceline Newsletter

Sign up for regular updates.