Biodiversity loss raises risk of 'extinction cascades'

February 19, 2018, University of Exeter

New research shows that the loss of biodiversity can increase the risk of "extinction cascades", where an initial species loss leads to a domino effect of further extinctions.

The researchers, from the University of Exeter, showed there is a higher risk of extinction cascades when other species are not present to fill the "gap" created by the loss of a species.

Even if the loss of one species does not directly cause knock-on extinctions, the study shows that this leads to simpler ecological communities that are at greater risk of "run-away extinction cascades" with the potential loss of many species.

With extinction rates at their highest levels ever and numerous species under threat due to human activity, the findings are a further warning about the consequences of eroding biodiversity.

"Interactions between species are important for ecosystem (a community of interacting species) stability," said Dr Dirk Sanders, of the Centre for Ecology and Conservation at the University of Exeter's Penryn Campus in Cornwall. "And because species are interconnected through multiple interactions, an impact on one species can affect others as well.

"It has been predicted that more complex food webs will be less vulnerable to extinction cascades because there is a greater chance that other species can step in and buffer against the effects of species loss.

"In our experiment, we used communities of plants and insects to test this prediction."

The researchers removed one species of wasp and found that it led to secondary extinctions of other, indirectly linked, species at the same level of the food web.

This effect was much stronger in simple communities than for the same species within a more complex food web.

Read more at: 

Rate of species decline 'no longer within safe limit' for humans, experts warn

'Until and unless we can bring biodiversity back up, we’re playing ecological roulette'

Ian Johnston Environment Correspondent 

Thursday 14 July 2016

Animal and plant species are declining so quickly that world biodiversity loss is no longer within a “safe limit” and could start to threaten much of the planet’s ability to support humans, according to a major new study.

Experts analysed nearly 2.4 million records about more than 39,000 species at 18,600 different places around the world.

They discovered that for 58.1 per cent of the world’s land surface the loss of biodiversity was serious enough to call into question its ability to sustain the 5.3 billion people who live there.

The research, published in the prestigious journal Science, comes as scientists are considering redefining the current geological epoch as the Anthropocene – because of humanity’s dramatic effects on the Earth, including what many fear will be the planet’s sixth mass extinction of life.

One of the researchers, Dr Tim Newbold, of University College London, said: “This is the first time we’ve quantified the effect of habitat loss on biodiversity globally in such detail and we’ve found that across most of the world biodiversity loss is no longer within the safe limit suggested by ecologists.

“We know biodiversity loss affects ecosystem function, but how it does this is not entirely clear. What we do know is that in many parts of the world, we are approaching a situation where human intervention might be needed to sustain ecosystem function.”

The “safe limit” was set at a 10 per cent reduction in species’ abundance, compared to the original number before humans took over the land. However, this definition is controversial as some researchers believe a reduction of 70 per cent would still be safe.

Read on … 

No returning to Eden: Researchers explore how to restore species in a changing world

Date:

July 24, 2014

Source:

University of Otago

Summary:

Reversing the increasing rate of global biodiversity losses may not be possible without embracing intensive, and sometimes controversial, forms of threatened species management, according to zoologists.

Continued

Bee and Wild Flower Biodiversity Loss Slows

May 22, 2013 — Declines in the biodiversity of pollinating insects and wild plants have slowed in recent years, according to a new study.

Researchers led by the University of Leeds and the Naturalis Biodiversity Centre in the Netherlands found evidence of dramatic reductions in the diversity of species in Britain, Belgium and the Netherlands between the 1950s and 1980s.

But the picture brightened markedly after 1990, with a slowdown in local and national biodiversity losses among bees, hoverflies and wild plants.

Professor Bill Kunin, Professor of Ecology at the University of Leeds, said: "Most observers have been saying that the 1992 Rio Earth Summit targets to slow biodiversity loss by 2010 failed, but what we are seeing is a significant slowing or reversal of the declines for wild plants and their insect pollinators.

"These species are important to us. About a third of our food production, including most of our fruit and vegetables, depends on animal pollination and we know that most crop pollination is done by wild pollinators. Biodiversity is important to ensuring we don't lose that service. Relying on a few species could be risky in a changing environment," he added.

Continued

Outbreak of chytrid fungus threatens Portugal’s Midwife toads

Toads have disappeared from 2/3rds of known habitats

December 2012. The emergence of chytridiomycosis is now widely recognized as a major cause of amphibian declines and biodiversity loss on local and global scales. Amphibian mortalities caused by the pathogenic chytrid fungus (Batrachochytrium dendrobatidis (Bd)) were first recorded in Iberia, Europe over a decade ago.

In August 2009, hundreds of post-metamorphic common Midwife toads (Alytes obstetricans) were found dead in the water and margins of a pond in the Serra da Estrela Natural Park, north-central Portugal, and analyses confirmed their infection with Bd. Given the likelihood of a new outbreak of chytridiomycosis, staff from Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, evaluated the possible impacts of this disease on populations of Midwife toads within the Park by conducting field surveys during 2010 and 2011.

They compared the present distribution and abundance of Midwife toads with historical records, and quantified the present prevalence and intensity of infection by Bd. Results showed that Midwife toads had disappeared from 67% of the 1 x 1 km squares where it had been recorded previously. Results also showed that breeding is currently limited to just 16% of the confirmed known breeding sites and that larvae are now less abundant. There is also a high incidence of Bd in the remaining sites.

These effects were most pronounced at altitudes above 1200 m. The findings suggest that an outbreak of chytridiomycosis is responsible for the rapid decline of Midwife toads in Serra da Estrela, and it is believed that urgent conservation measures are needed to prevent local extinction of the species.

Read the full scientific paper 

Continued:  http://www.wildlifeextra.com/go/news/portugal-midwife.html

Biodiversity Loss May Be Contributing to Amphibian-Killing Fungal Infection

ScienceDaily (Sep. 19, 2011) — Researchers at Oregon State University have shown for the first time that loss of biodiversity may be contributing to a fungal infection that is killing amphibians around the world, and provides more evidence for why biodiversity is important to many ecosystems.

The findings, being published this week in Proceedings of the National Academy of Sciences, used laboratory studies of amphibians to show that increased species richness decreased both the prevalence and severity of infection caused by the deadly chytrid fungus, Batrachochytrium dendrobatidis.

"With greater diversity of species, you get a dilution effect that can reduce the severity of disease," said Catherine Searle, an OSU zoologist and lead author on the study. "Some species are poor hosts, some may not get infected at all, and this tends to slow disease transmission.

"This has been shown in other systems like Lyme disease which infects humans, mice and deer," she said. "No one has really considered the dilution effect much in amphibians, which are experiencing population declines throughout the world. It's an underappreciated value of biodiversity."

It's generally accepted, the researchers said, that a high diversity of species can protect ecosystem function, help to recycle nutrients, filter air and water, and also protect the storehouse of plant or animal species that may form the basis of medicines, compounds or natural products of value to humans.

Protection against the spread of disease should more often be added to that list, they said.
"Emerging infectious diseases are on the rise in many ecosystems," said Andrew Blaustein, a co-author on this study, professor of zoology at OSU and leading researcher on the causes of amphibian declines.

"Protection of biodiversity may help reduce diseases," he said. "It's another strong argument for why diverse ecosystems are so important in general. And it's very clear that biodiversity is much easier to protect than it is to restore, once it's lost."

The fungus, B. dendrobatidis, can lead to death from cardiac arrest when it reaches high levels in its amphibian hosts. It is not always fatal at lower levels of infection, but is now causing problems around the world. One research team has called the impact of the chytrid fungus on amphibians "the most spectacular loss of vertebrate biodiversity due to disease in recorded history."

Amphibians face threats from multiple causes, including habitat destruction, pollution, increases in ultraviolet light due to ozone depletion, invasive species, and infectious disease.

The dilution effect can occur in plants and animals, but also in human diseases. In a different report published last year in Nature, researchers noted an increased risk of West Nile encephalitis in the U.S. in areas with low bird diversity. And in more diverse communities, the infection of humans by schistosomiasis -- which infects 200 million people worldwide -- can be reduced by 25-99 percent.

http://www.sciencedaily.com/releases/2011/09/110919151311.htm