Extinction .in

'Spineless' animals under threat of extinction

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A fifth of animals without backbones could be at risk of extinction, say scientists.

Almost 80% of the world's species are invertebrates, meaning they lack a

spinal column.

Reviewing over 12,000 species known to be threatened, biologists found that

freshwater ones are most at risk.

Researchers urged for comprehensive studies of those vulnerable, to help

inform conservation and protect species.

Human pressures, ranging from habitat disruption to

increased temperatures, were key concerns according to the report published by

the Zoological Society of London.

"We knew that roughly one fifth of vertebrates and plants were threatened

with extinction, but it was not clear if this was representative of the small

spineless creatures that make up the majority of life on the planet," said

Professor Jonathan Baillie, ZSL's director of conservation.

"The initial findings in this report indicate that 20% of all species may be

threatened.

"This is particularly concerning as we are dependent on these spineless

creatures for our very survival," he said.

The majority of the world's estimated 126,000 freshwater species are

invertebrates including molluscs and insects, such as dragonflies.

Of those included on the International Union for the Conservation of Nature's

(IUCN's) Red List of Threatened Species, 35% are considered threatened and 131

species are listed as Extinct.

According to the ZSL review, a major issue for

threatened freshwater species is water pollution from agricultural run-off,

domestic sewage and industrial waste.

Damming and the removal of water, in addition to human settlements disrupting

habitat, are also adding pressure for the freshwater crabs, crayfishes,

molluscs, dragonflies and damselflies included in the assessment.

"They're important because they play a number of roles in eco-systems that

provide humans with great benefits," said Dr. Ben Collen, head of the Indicators

and Assessments unit at ZSL.

"Invertebrates are particularly good at providing things like water

filtration and nutrient recycling."

The picture for marine invertebrates however is less clear. Of the species

assessed by the IUCN, 25% are said to be at risk of extinction but the list only

covers 1% of all described species.

"Our marine system is the least well-known system, so there's lots more work

to be done in terms of discovering what's out there let alone what's happening

to it," said Dr Collen.

"It's plausible that threat levels could be higher, particularly with threats

that have no real boundaries like ocean acidification."

According to Dr Collen, this ongoing process, where the pH levels of the

ocean rise in response to increases in atmospheric CO2, could be particularly

harmful for species with external skeletons that can be eroded.

Complete global assessments of reef-building corals, lobsters, and cuttlefish

have been achieved and comprehensive work on squids, octopuses, cone snails,

reef building oysters and sea cucumbers is nearing completion.

But the report urged studies on other groups, including the iconic living

fossils known as nautiluses.

Having survived relatively unchanged for millions of years, the animals are

now the subject of concern for some as they are commonly collected for both

shell curios and the pet trade.

According to ZSL, nautiluses could be particularly vulnerable to this

pressure due to their low populations and slow rates of reproduction.

Chamber of secrets

Nautiluses move through the water by pumping air into and out of gas filled

chambers within their shells

"From the marine species that we assessed, the ones that

we're most concerned about are the ones which are exploited - things like

lobsters and crabs and species of shellfish," said Dr Collen.

On land, invertebrates such as insects, molluscs and worms make up 96% of all

known species.

The ZSL report describes many as having "bizarre" appearances due to their

specialist adaptations to live in a particular habitats.

But scientists said that this extreme attention to habitat also heightens

many species' sensitivity to change.

Forty-two percent of the species currently listed by the IUCN are considered

under threat but, again, the assessed animals only represent a tiny proportion

(0.3%) of the total described species.

"Invertebrates tend to go under the radar, people don't realise just how

integral they are," said Dr Collen.

"All of the flowers that we see around us, many of the crops that we grow and

eat are pollinated for free by insects."

"Invertebrates form quite a big part of people's diets in certain parts of

the world, they form parts of systems that recycle nutrients [and] they're part

of the forest systems that stores carbon."

"They are very much the architects of a lot of these eco-system

services."

He told BBC Nature that the role of terrestrial invertebrates was "more

immediately obvious" to us because of their proximity.

In the report, scientists have included calculations of the rarely recognised

economic worth of the animals.

For example, in 2007 honeybees' role as pollinators was worth £200m to the UK

economy according to The National Audit Office.

"The things that [invertebrates] do are worth billions of dollars per year to

the global economy and at the moment those costs aren't factored into

decisions," said Dr Collen.

"We're not genuinely thinking about what the environment provides for us so

putting a monetary value on eco-system services is one way [conservationists]

can help to do that."

"While the cost of saving [invertebrates] will be expensive, the cost of

ignorance to their plight appears to be even greater," said Dr Collen.