Climate-Driven Biodiversity Loss Will Be Sudden, Study Warns
That's the warning from a new study published in Nature Wednesday, which set out to determine how a variety of species and ecosystems would respond to rising temperatures over the course of the 21st century.
"We found that climate change risks to biodiversity don't increase gradually. Instead, as the climate warms, within a certain area most species will be able to cope for a while, before crossing a temperature threshold, when a large proportion of the species will suddenly face conditions they've never experienced before," lead author Dr. Alex Pigot of University College London's Centre for Biodiversity & Environment Research said in a press release. "It's not a slippery slope, but a series of cliff edges, hitting different areas at different times."
The researchers divided the globe into 100 by 100 kilometer (approximately 62 mile) grids and looked at the ranges of 30,652 species along with climate models from 1850 to 2005. They then used models to determine when the species in each grid would experience temperatures beyond their historic ranges for five years or more. The results showed that many species in an ecosystem would cross that temperature threshold at the same time, and 73 percent of species around the world facing temperature shocks would do so in the same decade.
Key finding is that in any location, species may occur within their niche limits for a while, but then a threshold… https://t.co/Q39HJGp9qT— Alex Pigot (@Alex Pigot)1586358090.0
Jennifer Sunday, a McGill University biologist who was not involved with the study, told InsideClimate News that its novel approach allowed for new insight into the timeline for climate-driven biodiversity loss.
"We did not know about the time-course of events. We have lots of models that compare species ranges today to those at a future date, but we did not know when most of the changes were going to happen," she said. "The research also makes it clear that global warming's impacts on ecosystems could arrive very suddenly."
Just how sudden and how devastating those impacts will be depends entirely on how swiftly greenhouse gas emissions are lowered to reduce global warming.
The study found that, in a high-emissions scenario that allows more than four degrees Celsius of warming by 2100, at least 15 percent of ecosystems would suffer an event in which more than 20 percent of their key species hit their temperature limits in the same decade. This could happen before 2030 for tropical oceans and by 2050 for the far North and tropical forests.
If emissions are kept below two degrees Celsius, however, as per the goals of the Paris agreement, fewer than two percent of ecosystems will face such an event.
This early projected onset of exposure is consistent with the recurrent mass bleaching of coral reefs which are hap… https://t.co/HN2UrsmHBp— Alex Pigot (@Alex Pigot)1586358092.0
Dr. Pigot said the experience of the coronavirus provided a model for how swift action now could avert catastrophe later.
"Our findings highlight the urgent need for climate change mitigation, by immediately and drastically reducing emissions, which could help save thousands of species from extinction. Keeping global warming below 2°C effectively 'flattens the curve' of how this risk to biodiversity will accumulate over the century, providing more time for species and ecosystems to adapt to the changing climate – whether that's by finding new habitats, changing their behaviour, or with the help of human-led conservation efforts," he said in the press release.
Conservation groups also endorsed Pigot's message.
"There is already more than enough evidence that climate change is impacting the natural world and that we risk losing up to a million species. We know what the solutions are to halt climate change and biodiversity loss," Mark Wright, director of science at WWF-UK, told The Guardian. "The world is currently rightly focused on tackling the global health emergency. However, this new research reinforces that, after we are through this extremely difficult time, we will need renewed ambitious action to address the climate and nature crisis."
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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.
"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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