One-fifth of the "spineless creatures that rule the world" may be at risk of extinction, according to a new study.

The 87-page report found the rising human population is putting ever more pressure on creatures like slugs, spiders, jellyfish, lobsters, corals, and bugs such as beetles and butterflies.

The report said that invertebrates - creatures that have no internal skeleton - are facing loss of habitat, pollution, over-exploitation and climate change.

The study, produced with the International Union for Conservation of Nature, could also have implications for humans.

"The invertebrates are the ecosystem engineers," said Ben Collen at the Zoological Society of London (ZSL).

"They produce a lot of the things that humans rely on and they produce them for free."

The services they provide - helping humans whose growing numbers threaten their survival - include water purification, pollination, waste recycling, and keeping soils productive.

For instance, earthworms recycle waste and bees pollinate crops.

http://www.abc.net.au/news/2012-08-31/spineless-creatures-at-risk/4237464