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Protecting Wetlands Yields Staggering Economic Benefit, Study Finds

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Protecting Wetlands Yields Staggering Economic Benefit, Study Finds
Orlando Wetlands Park in central Florida. Bkamprath / iStock/ Getty Images Plus

By Kimberly M.S. Cartier

Mangrove forests, marshes and seagrass beds protect inland areas from storm surges and strong winds. Over long periods, coastal wetlands like these build up sediment that mitigates sea level rise and local land subsidence.


A new analysis of property damage from Atlantic and Gulf of Mexico coastal storms has shown that counties with larger wetlands suffered lower property damage costs than did counties with smaller wetlands.

"Starting in 1996, the U.S. government started to produce damage estimates for each tropical cyclone in a consistent manner," explained coauthor Richard Carson, an economist at the University of California, San Diego (UCSD) in La Jolla. Before that, the data were collected only for hurricanes, which hindered past attempts to put a price on the marginal value, or price per unit, of wetlands, he said.

With the complete data set, the researchers examined all 88 tropical cyclones and hurricanes that affected the U.S. starting in 1996. That time period includes Hurricanes Katrina and Sandy.

A Protective and Economic Boon

In addition to property damage data for tropical cyclones of all strengths, "our data set has considerably more spatial resolution," Carson said, "which is a result of large amounts of information on storm tracks, property location, and wetland location all being digitized for use in a geographical information system basis."

First author Fanglin Sun, formerly at UCSD and now an economist at Amazon.com, added that "areas subject to flood risk in a county are more accurately estimated, based on local elevation data and detailed information on individual storm trajectories" and wind speeds throughout affected areas.

The finer level of detail for the storm data let the researchers finally begin connecting wetland coverage and storm damage on a county-by-county basis, Carson said. "A storm track moving a couple of kilometers one direction or the other allows the amount of wetland protection to vary within the same county."

In terms of property damage, Sun and Carson found that a square kilometer of wetlands saved an average of $1.8 million per year. Over the next 30 years, an average unit of wetlands could save $36 million in storm damage.

Some wetlands were valued at less than $800 per year per square kilometer and some at nearly $100 million. That marginal value depended on many factors, including a county's property values, existing wetland coverage, coastline shape, elevation, building codes, and chance of actually experiencing damaging winds. And each of those variables fluctuated over the 20 years the team studied.

Overall, the highest-valued wetlands were in urban counties with large populations and the lowest-valued were in rural areas with small populations. However, wetlands provided a greater relative savings against weaker cyclones and in counties with less stringent building codes — areas that might not expect or plan for a tropical storm.

The team found no significant difference in the marginal value of saltwater versus freshwater wetlands or mangroves versus marshes. "Forested wetlands tend to be better at reducing wind speed and marshes tend to be better at absorbing water," Carson said, "so the specific nature of the storm when it hits an area is likely to matter. [But] our results suggest that, on average, there is no difference."

The team published these results in Proceedings of the National Academy of Sciences of the United States of America on March 3.

Wetlands at Risk

Most areas that have experienced storm-related property damage in the past 20 years have also lost wetland coverage, the researchers found. They calculated that Floridians would have been spared $480 million in property damage from Hurricane Irma alone had the state's wetland coverage not shrunk by 2.8% in the decade prior.

Moreover, recent changes to the Clean Water Act have made the remaining coastal wetlands more vulnerable.

"The federal government, with respect to the U.S. Clean Water Act, took the position that the previous wetland studies were not reliable enough for use in assessing the benefits and cost of protecting wetlands," Carson said.

"The value coastal wetlands provide for storm protection is substantial and should be taken into account as policy makers debate the Clean Water Act," Sun said. "It's also worth noting," she added, "that storm protection for property is just one of many ecological services that wetlands provide. We hope our study will spur future research quantifying these other services as well."

With tropical storms and hurricanes expected to happen more often because of climate change, the team wrote, wetlands will be more economically valuable than ever.

Reposted with permission from The Revelator.

A net-casting ogre-faced spider. CBG Photography Group, Centre for Biodiversity Genomics / CC BY-SA 3.0

Just in time for Halloween, scientists at Cornell University have published some frightening research, especially if you're an insect!

The ghoulishly named ogre-faced spider can "hear" with its legs and use that ability to catch insects flying behind it, the study published in Current Biology Thursday concluded.

"Spiders are sensitive to airborne sound," Cornell professor emeritus Dr. Charles Walcott, who was not involved with the study, told the Cornell Chronicle. "That's the big message really."

The net-casting, ogre-faced spider (Deinopis spinosa) has a unique hunting strategy, as study coauthor Cornell University postdoctoral researcher Jay Stafstrom explained in a video.

They hunt only at night using a special kind of web: an A-shaped frame made from non-sticky silk that supports a fuzzy rectangle that they hold with their front forelegs and use to trap prey.

They do this in two ways. In a maneuver called a "forward strike," they pounce down on prey moving beneath them on the ground. This is enabled by their large eyes — the biggest of any spider. These eyes give them 2,000 times the night vision that we have, Science explained.

But the spiders can also perform a move called the "backward strike," Stafstrom explained, in which they reach their legs behind them and catch insects flying through the air.

"So here comes a flying bug and somehow the spider gets information on the sound direction and its distance. The spiders time the 200-millisecond leap if the fly is within its capture zone – much like an over-the-shoulder catch. The spider gets its prey. They're accurate," coauthor Ronald Hoy, the D & D Joslovitz Merksamer Professor in the Department of Neurobiology and Behavior in the College of Arts and Sciences, told the Cornell Chronicle.

What the researchers wanted to understand was how the spiders could tell what was moving behind them when they have no ears.

It isn't a question of peripheral vision. In a 2016 study, the same team blindfolded the spiders and sent them out to hunt, Science explained. This prevented the spiders from making their forward strikes, but they were still able to catch prey using the backwards strike. The researchers thought the spiders were "hearing" their prey with the sensors on the tips of their legs. All spiders have these sensors, but scientists had previously thought they were only able to detect vibrations through surfaces, not sounds in the air.

To test how well the ogre-faced spiders could actually hear, the researchers conducted a two-part experiment.

First, they inserted electrodes into removed spider legs and into the brains of intact spiders. They put the spiders and the legs into a vibration-proof booth and played sounds from two meters (approximately 6.5 feet) away. The spiders and the legs responded to sounds from 100 hertz to 10,000 hertz.

Next, they played the five sounds that had triggered the biggest response to 25 spiders in the wild and 51 spiders in the lab. More than half the spiders did the "backward strike" move when they heard sounds that have a lower frequency similar to insect wing beats. When the higher frequency sounds were played, the spiders did not move. This suggests the higher frequencies may mimic the sounds of predators like birds.

University of Cincinnati spider behavioral ecologist George Uetz told Science that the results were a "surprise" that indicated science has much to learn about spiders as a whole. Because all spiders have these receptors on their legs, it is possible that all spiders can hear. This theory was first put forward by Walcott 60 years ago, but was dismissed at the time, according to the Cornell Chronicle. But studies of other spiders have turned up further evidence since. A 2016 study found that a kind of jumping spider can pick up sonic vibrations in the air.

"We don't know diddly about spiders," Uetz told Science. "They are much more complex than people ever thought they were."

Learning more provides scientists with an opportunity to study their sensory abilities in order to improve technology like bio-sensors, directional microphones and visual processing algorithms, Stafstrom told CNN.

Hoy agreed.

"The point is any understudied, underappreciated group has fascinating lives, even a yucky spider, and we can learn something from it," he told CNN.

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