Dragonflies are on the brink of extinction

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Dragonflies are on the brink of extinction

Postby Squire » 15 Oct 2017, 19:21

This article is about British dragonflies, however, the same causes are threatening the extinction of dragonflies around the world.

In the past year, I recall only seeing a small dragonfly on two occasions. When I was a child there were swarms of thousands of dragonflies.

https://www.theguardian.com/environment/2009/jul/25/dragonfly-sanctuary

Dragonflies in danger of extinction seek sanctuary at new rescue centre
Pollution, pesticides and habitat loss bring dragonflies close to the brink after 325m years

Dragonflies may have hovered and hunted across the planet for the last 325m years, but their modern relatives are staring extinction in the face. Experts warn that one-third of British species are now under threat, a plight that today sees the opening of the UK's first ever dragonfly centre to celebrate and protect one of the country's most fascinating insects.

Located at Wicken Fen nature reserve in Cambridgeshire, the new centre hopes to reverse the decline of the 42 species found regularly in the UK. Conservationists blame the decline on the loss of wetlands, and pesticides and insecticides drifting from farmland.

Springwatch presenter Chris Packham, who opened the centre today, said: "The loss of wetland habitat throughout the UK is having a massive impact on the long-term survival prospects for many dragonfly species." He warned that three British species have already become extinct since the 1960s.


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Dragonflies spend much of their lives underwater as larva "nymphs", and when the winged adult finally emerges its flying lifetime is comparatively short, ranging from just weeks for small species to a few years for the largest. They are a key indicator of water quality and a valuable natural predator of mosquitoes and midges.

Some British species are faring worse than others. White-faced darters have seen a signifcant loss and drying out of the bog pools where they live, while the Norfolk hawker's limited distribution - mostly in the Norfolk Broads - has left it vulnerable to sea level rises and salt water infiltration...
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Re: Dragonflies are on the brink of extinction

Postby HBS Guy » 15 Oct 2017, 19:49

We are fucking Mother Nature and will live (maybe) to regret it.
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Re: Dragonflies are on the brink of extinction

Postby mothra » 16 Oct 2017, 15:55

We are doing inestimable damage, there is no question.

Did you now that female dragonflies feign death to avoid amorous males they don't want to mate with? To the point of actually dropping out of the sky.
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Re: Dragonflies are on the brink of extinction

Postby HBS Guy » 16 Oct 2017, 16:00

I hoped my pond might attract some but I guess it is just too small. The native fish in there might eat the larva too.
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Re: Dragonflies are on the brink of extinction

Postby mothra » 16 Oct 2017, 16:04

HBS Guy wrote:I hoped my pond might attract some but I guess it is just too small. The native fish in there might eat the larva too.



Yeah, i'd definitely say the fish would eat the larvae.

They eat the mozzie larvae too, bless 'em.
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Re: Dragonflies are on the brink of extinction

Postby HBS Guy » 16 Oct 2017, 16:09

Yeah, bet lots of mozzies visit my pond to give the fish their dinner :jump

Got Flinders Ranges Purple Gudgeon and Murray River Rainbows. Think they eat the eggs/hatchlings too, that or I have SSM happening in my pond!

NO carp!
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All flying insects are experiencing severe population declin

Postby Squire » 19 Oct 2017, 12:42

This story from German research publishes that a population decline of 76% in flying insects in a national park over a period of 17 years. The attrition rate must be worse outside national parks.

https://www.washingtonpost.com/news/speaking-of-science/wp/2017/10/18/this-is-very-alarming-flying-insects-vanish-from-nature-preserves/?utm_term=.5a4b8b38daff

‘This is very alarming!’: Flying insects vanish from nature preserves
By Ben Guarino October 18 at 2:00 PM

The white tent of a malaise trap in a nature reserve abutting farmland. (Verein Krefeld, entomologist)
Not long ago, a lengthy drive on a hot day wouldn't be complete without scraping bug guts off a windshield. But splattered insects have gone the way of the Chevy Nova — you just don't see them on the road like you used to.

Biologists call this the windshield phenomenon. It's a symptom, they say, of a vanishing population.

“For those of us who look, I think all of us are disturbed and all of us are seeing fewer insects,” said Scott Black, executive director of the Portland, Ore.-based Xerces Society, a nonprofit environmental group that promotes insect conservation. “On warm summer nights you used to see them around streetlights.”

The windshield phenomenon is not just a trick of Trans Am nostalgia. A small but growing number of scientific studies suggest that insects are on the wane.

“The windscreen phenomenon is probably one of the best illustrative ways to realize we are dealing with a decline in flying insects,” said Caspar Hallmann, an ecologist at Radboud University in the Netherlands. Hallmann is part of a research team that recently waded through 27 years' worth of insects collected in German nature preserves.

Between 1989 and 2016, according to a report published Wednesday in the journal PLOS One, the biomass of flying insects captured in these regions decreased by a seasonal average of 76 percent.

John Losey, an entomologist at Cornell University in New York who was not involved with this study, said he was impressed by the scope of the new research across time, space and habitat range. Insects were collected at 63 locations in Germany, including grasslands, swamps, sand dunes, wastelands, shrub land and along the margins of human settlement.

All of the locations were protected areas. “This decline happened in nature reserves, which are meant to preserve biodiversity and ecosystem functioning,” Hallmann said. “This is very alarming!”

Though some missing insects may be pests — bloodsuckers or crop-eaters — plenty of insects are productive members of a healthy ecosystem. (Even mosquitoes play a vital role as food sources for fish and other animals.) In 2006, Losey and fellow Cornell entomologist Mace Vaughan estimated that wild insects provide $57 billion worth of custodial services in the United States each year. They bury animal dung, prey on pests and pollinate plants.

“If you like to eat nutritious fruits and vegetables, you should thank an insect. If you like salmon, you can thank a tiny fly that the salmon eat when they're young,” Black said. “The whole fabric of our planet is built on plants and insects and the relationship between the two.”

The Obama administration announced the first national strategy to promote the health of bees and other pollinators, following the sharp decline in colony numbers in recent years. USDA bee scientist Jay Evans explains why honeybees are so important and how bees affect food prices. (Alice Li/The Washington Post)

Decrease of flying insects, in grams per day. (Radboud University)

What made this research particularly remarkable, Losey said, was the extent of the observed decline. Other estimates have put rates of global insect biomass loss at 50 percent or less — disturbing, but not as dismaying as the results from the German fieldwork.

Researchers caught insects in what's called a malaise trap. Insects fly into the tented fabric, which funnels them into a collecting jar. The scientist gauged bug captures by mass. It's an assessment of abundance, not diversity, a measure that scientists call biomass. At the end of 27 years, the insect biomass totaled nearly 54 kilograms — a weight of 120 pounds. The study authors said this mass represented millions of insects.

“Malaise traps are very good at catching flies and some other small flying insects but do not catch larger-bodied flying insects very well,” said James Pryke, a conservationist and entomologist at Stellenbosch University in South Africa who was not involved in this study. “This is not a criticism of the study but a comment that these results are most likely from a reduction in the number of flies,” he said, particularly midges and other “gregarious flies.”

The most dramatic reduction over time in bug biomass appeared in summer months, when insects should be most active. “Apparently, when insect densities are the highest, declines are most severe. Unfortunately we do not know why,” Hallmann said.

Previous research focused on certain groups of insects, such as ladybugs or California's monarch butterflies, have also revealed sharp declines. “I’m not seeing any study that is showing insects are doing very well,” Black said.

Hallmann said the German study should be “representative for parts of the world under similar conditions,” which is to say a human-dominated landscape coupled with intensive agriculture. But he cannot make more-specific comparisons, because “similar data sets do not exist elsewhere, to our knowledge,” he said.

The authors of the new study attempted to tease out the roots of the decline. The scientists' investigation into climatic changes and other variables, however, eliminated most “prime suspects,” Hallmann said. (In fact, the temperature increase observed over the study period should have benefited flying insects, he said.)
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Re: Dragonflies are on the brink of extinction

Postby HBS Guy » 19 Oct 2017, 13:26

GMO crops in massive plantings.

Neonicotinoid pesticides

AGW (effects the timing of seasons, growth of plants/animals the insect depends on, timing of predators arriving etc)

And national parks (here in Oz anyway) are havens for feral plant and animal pests.
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