Featured Research

from universities, journals, and other organizations

Humans threaten wetlands' ability to keep pace with sea-level rise

Date:
December 4, 2013
Source:
Virginia Institute of Marine Science
Summary:
Left to themselves, coastal wetlands can withstand rapid levels of sea-level rise. But humans could be sabotaging some of their best defenses, according to a new review.

Low-elevation wetland: Low-elevation wetlands like this Spartina marsh in Massachusetts' Plum Island Estuary are frequently flooded by tides that deposit sediment and cause the marsh to build up at a fast rate (approximately 5-10 millimeters per year).
Credit: Matt Kirwan

Left to themselves, coastal wetlands can resist rapid levels of sea-level rise. But humans could be sabotaging some of their best defenses, according to a Nature review paper published December 5 from the Virginia Institute of Marine Science and the Smithsonian Environmental Research Center.

The threat of disappearing coastlines has alerted many to the dangers of climate change. Wetlands in particular -- with their ability to buffer coastal cities from floods and storms, and filter out pollution -- offer protections that could be lost in the future. But, say co-authors Matt Kirwan and Patrick Megonigal, higher waters aren't the key factor in wetland demise. Thanks to an intricate system of feedbacks, wetlands are remarkably good at building up their soils to outpace sea level rise. The real issue, they say, is that human structures such as dams and seawalls are disrupting the natural mechanisms that have allowed coastal marshes to survive rising seas since at least the end of the last Ice Age.

"Tidal marsh plants are amazing ecosystem engineers that can raise themselves upward if they remain healthy, and especially if there is sediment in the water," says co-author Patrick Megonigal of the Smithsonian Environmental Research Center. "We know there are limits to this, and worry those limits are changing as people change the environment."

"In a more natural world, we wouldn't be worried about marshes surviving the rates of sea level rise we're seeing today," says Kirwan, the study's lead author and a geologist at the Virginia Institute of Marine Science. "They would either build vertically at faster rates or else move inland to slightly higher elevations. But now we have to decide whether we'll let them."

Wetlands have developed several ways to build elevation to keep from drowning. Above ground, tidal flooding provides one of the biggest assists. When marshes flood during high tide, mineral sediment settles out of the water, adding new soil to the ground. It's one of the more convenient response systems to today's threat: When sea level rise accelerates and flooding occurs more often, marshes can react by building soil faster. Below ground, the growth and decay of plant roots adds organic matter -- an effect rising carbon dioxide (CO2) seems to enhance. Even erosion can work in favor of wetlands, as sediment lost at one marsh can be deposited on another. While a particular wetland may lose ground, the total wetland area may remain unchanged.

But everything has a threshold. If a wetland becomes so flooded that vegetation dies off, the positive feedback loops are lost. Similarly, if sediment delivery to a wetland is cut off, that wetland can no longer build soil to outpace rising seas.

Direct human impacts, not rising seas or rising CO2, have the most power to alter those thresholds, the scientists report. Groundwater withdrawal and artificial drainage can cause the land to sink, as is happening right now in Chesapeake Bay. Because of this kind of subsidence, 8 of the world's 20 largest coastal cities are experiencing relative sea-level rise greater than climate change projections. Dams and reservoirs also prevent 20 percent of the global sediment load from reaching the coast. Marshes on the Yangtze River Delta survived relative sea-level rise of more than 50 mm per year since the 7th century C.E., until the building of more than 50,000 dams cut off their supply of sediment and sped up erosion.

In addition to building vertically, marshes can also respond to sea-level rise by migrating landward. But, the authors note, human activities have hindered this response as well. Conventional ways of protecting coastal property, such dykes and seawalls, keep wetlands from moving inland and create a "shoreline squeeze," Kirwan says. Because rates of marsh-edge erosion increase with rates of sea-level rise, the authors warn that the impacts of coastal barriers will accelerate with climate change.


Story Source:

The above story is based on materials provided by Virginia Institute of Marine Science. The original article was written by Kristen Minogue, SERC. Note: Materials may be edited for content and length.


Journal Reference:

  1. Matthew L. Kirwan, J. Patrick Megonigal. Tidal wetland stability in the face of human impacts and sea-level rise. Nature, 2013; 504 (7478): 53 DOI: 10.1038/nature12856

Cite This Page:

Virginia Institute of Marine Science. "Humans threaten wetlands' ability to keep pace with sea-level rise." ScienceDaily. ScienceDaily, 4 December 2013. <www.sciencedaily.com/releases/2013/12/131204132024.htm>.
Virginia Institute of Marine Science. (2013, December 4). Humans threaten wetlands' ability to keep pace with sea-level rise. ScienceDaily. Retrieved April 16, 2014 from www.sciencedaily.com/releases/2013/12/131204132024.htm
Virginia Institute of Marine Science. "Humans threaten wetlands' ability to keep pace with sea-level rise." ScienceDaily. www.sciencedaily.com/releases/2013/12/131204132024.htm (accessed April 16, 2014).

Share This



More Earth & Climate News

Wednesday, April 16, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Change of Diet Helps Crocodile Business

Change of Diet Helps Crocodile Business

Reuters - Business Video Online (Apr. 16, 2014) Crocodile farming has been a challenge in Zimbabwe in recent years do the economic collapse and the financial crisis. But as Ciara Sutton reports one of Europe's biggest suppliers of skins to the luxury market has come up with an unusual survival strategy - vegetarian food. Video provided by Reuters
Powered by NewsLook.com
How Mt. Everest Helped Scientists Research Diabetes

How Mt. Everest Helped Scientists Research Diabetes

Newsy (Apr. 15, 2014) British researchers were able to use Mount Everest's low altitudes to study insulin resistance. They hope to find ways to treat diabetes. Video provided by Newsy
Powered by NewsLook.com
The Walking, Talking Oil-Drigging Rig

The Walking, Talking Oil-Drigging Rig

Reuters - Business Video Online (Apr. 15, 2014) Pennsylvania-based Schramm is incorporating modern technology in its next generation oil-drigging rigs, making them smaller, safer and smarter. Ernest Scheyder reports. Video provided by Reuters
Powered by NewsLook.com
In Washington, a Push to Sterilize Stray Cats

In Washington, a Push to Sterilize Stray Cats

AFP (Apr. 14, 2014) To curb the growing numbers of feral cats in the US capital, the Washington Humane Society is encouraging residents to set traps and bring the animals to a sterilization clinic, after which they are released.. Duration: 02:29 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins