Invertebrate numbers have fallen by nearly half over the last 35 years

The world's soaring human population has slashed the numbers of creepy crawlies a study has found. However, researchers say the demise of slugs, spiders and worms is not good news for us humans and could spark an explosion in pests. The study, published in the journal Science, revealed that as the human population has doubled over the last 35 years to now stand at more than seven billion, invertebrate numbers have fallen by nearly half over the same period. Experts fear this could have an effect on ecosystems as insects, spiders, crustaceans slug and worms play an important role in pollinating crops, pest control, decomposition and ensuring soil remains packed with nutrients, as well as water filtration. In the UK these two factors caused a massive reduction in the number of beetles, butterflies, bees and wasps, a 30-60 percent fall over 40 years, according to the study.

Experts warned that fewer insects would have a huge effect on crop production as up to 75 per are pollinated by insects, amounting to around 10 per cent of the world's food supply.
And the cost of pest control without natural predators could be more than £2.6 billion pounds in the United States alone.
Scientists also fear the consequences of a world with fewer birds and insects to recycle and move nutrients, and say it would result in a less reliable food supply.
With fewer amphibians it is also feared that we could end up with more algae clogging up our water supply.
Decreasing invertebrate numbers are also known to compromise food production due to reduced pollination, seed dispersal and insect predation but the impact the continuing loss of animals, including invertebrates, has on the spread of human disease needs to be better understood as a priority.
Dr Ben Collen, from University College London's Biosciences Department, said: "We were shocked to find similar losses in invertebrates as with larger animals, as we previously thought invertebrates to be more resilient.
"While we don't fully understand what the long-term impact of these declining numbers will be, currently we are in the potentially dangerous position of losing integral parts of ecosystems without knowing what roles they play within it.
"Prevention of further declines will require us to better understand what species are winning and losing in the fight for survival and from studying the winners, apply what we learn to improve conservation projects.
"We also need to develop predictive tools for modelling the impact of changes to the ecosystem so we can prioritise conservation efforts, working with governments globally to create supportive policy to reverse the worrying trends we are seeing."
Lead author Prof Rodolfo Dirzo, of Stanford Woods Institute for the Environment in the US, added: "Where human density is high, you get high rates of defaunation, high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission.
"Who would have thought that just defaunation would have all these dramatic consequences, but it can be a vicious circle.
"We tend to think about extinction as loss of a species from the face of Earth, and that's very important, but there's a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well.
"Ironically, we have long considered that defaunation is a cryptic phenomenon, but I think we will end up with a situation that is non-cryptic because of the increasingly obvious consequences to the planet and to human well-being."

Source: Telegraph, 25 July 2014
http://www.telegraph.co.uk/earth/wildlife/10989198/Creepy-crawlies-decl…