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Island Trees Have Nowhere to Run From Climate Change

Climate
Island Trees Have Nowhere to Run From Climate Change
A small Bermuda cedar tree sits atop a rock overlooking the Atlantic Ocean. todaycouldbe / iStock / Getty Images Plus

By Marlene Cimons

Kyle Rosenblad was hiking a steep mountain on the island of Maui in the summer of 2015 when he noticed a ruggedly beautiful tree species scattered around the landscape. Curious, and wondering what they were, he took some photographs and showed them to a friend. They were Bermuda cedars, a species native to the island of Bermuda, first planted on Maui in the early 1900s.


"Sometimes, island species are transported by humans outside their native islands — either to a mainland continent or to another island — and manage to survive in the wild there, as the Bermuda cedar has done on Maui," said Rosenblad, a research associate with the Sax Lab at Brown University's department of ecology and evolutionary biology.

He had never been to Bermuda, but suspected its climate was different from Maui's. "Then it hit me: if my suspicion was correct, then this species, by succeeding in Maui's climate, was effectively showing us its biological buffer that might help it survive future climate change," Rosenblad said."However, we still didn't know whether this buffer would be wide enough to accommodate the changes in climate expected to occur on Bermuda."

In other words, the Bermuda cedar could cope with life on Maui, but that doesn't mean it could cope with life in Bermuda later this century.

A Bermuda beach

Pixabay

Existing research shows that island species are less diverse than their cousins on the mainland. That lack of diversity makes them vulnerable to changing conditions. On an island, for instance, every member of a particular tree species might be suited to cool weather, whereas on the mainland, some are suited to the cold, while others are built for the heat. If temperatures rise, at least some of the mainland trees, those built for warm weather, might endure, but the island trees could perish.

"If climate change makes a given island too warm for the species that live there — or too dry or too stormy — then those species will be stuck on their island with nowhere to escape," Rosenblad said.

Rosenblad and his colleagues — Dov Sax, head of the Sax Lab, and doctoral student Daniel Perret — investigated the dangers that climate change poses to island species by studying conifers, a group that includes cedars, firs and pines. "When unique island tree species are given a chance to grow outside their native islands, how much extra climate hardiness do they show?" Rosenblad said. "And will that extra hardiness be sufficient to help them survive predicted future changes in climate?"

Branches of a Bermuda cedar

Malcolm Manners

What they found was troubling. Their work suggests that climate change could push many small island conifers — nearly a quarter of those they studied — into extinction by 2070. The smaller the island the more danger, as trees have nowhere to flee. The larger the island, the more varied the climate, meaning species can relocate to cooler areas. Their research appears in the journal Nature Climate Change.

"Our results took us by surprise," Rosenblad said. "We expect if these species are left to fend for themselves, climate change will eventually drive them extinct."

Species can adapt to new conditions, but climate change will make that difficult. "The rub is that for some species, the amount of hardiness and adaptability they have shown is still not enough to buffer them against the changes in climate that are expected to occur on their native islands," Rosenblad said.

Canary Island pine trees, one of the conifers used in the study

Luc Viatour

So, while the Bermuda cedar may thrive on Maui, adapting to the future climate of Bermuda "will require an even bigger stretch," he added. He added that while the Bermuda cedar is surviving in many different places, "sadly none of them has a climate that resembles the one that Bermuda is projected to have in 50 years." That being the case, he said, "we still don't have any evidence that it can handle the climatic changes that are expected to occur on its native island."

The scientists urged caution in interpreting the findings, as species might be hardier that the evidence suggests. "However, I still find our results highly concerning," Rosenblad said.

In conducting their study, the researchers relied upon data obtained from global digitized plant specimen collections. Focusing on 55 species of coniferous trees, they cross-referenced information about them with existing worldwide climate statistics to determine the climate conditions, such as temperature and precipitation, at each location where their study species were found, including their native islands and other sites. They then built computer models for each species which told the researchers how the species would fare under different combinations of climatic conditions, including climate conditions projected for their native islands in 50 years.

Norfolk Island pines, one of the conifers used in the study

Bertknot

Researchers said many island tree species likely will require "serious help" withstanding climate change. "Failing to provide this help could have dire consequences, not just for the tree species themselves," he said. Trees perform essential functions, he explained, "like helping to regulate the flows of water and nutrients through the ecosystem."

Researchers called for targeted conservation efforts to avert extinction. Moreover, many of these trees also are culturally significant to island residents, especially the Bermuda cedar.

"It remains an indelible Bermudian cultural symbol," Rosenblad said. "Its wood has long been prized by artisans and builders. There is even a Bermudian wedding tradition, in which the cake is presented carrying a cedar seedling on top, and the couple then plants the seedling together."

He added, " It's important to underscore the beauty of these trees — and help them avoid extinction — so future generations can benefit from all they have to offer."

Reposted with permission from our media associate Nexus Media.

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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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