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Global insect decline may see 'plague of pests'

By Matt McGrath  Environment correspondent

Global insect decline may see 'plague of pests'

butterfliesImage copyrightGETTY IMAGES
Image captionMany species of butterfly are in retreat according to the review

A scientific review of insect numbers suggests that 40% of species are undergoing "dramatic rates of decline" around the world.

The study says that bees, ants and beetles are disappearing eight times faster than mammals, birds or reptiles.

But researchers say that some species, such as houseflies and cockroaches, are likely to boom.

The general insect decline is being caused by intensive agriculture, pesticides and climate change.

Insects make up the majority of creatures that live on land, and provide key benefits to many other species, including humans.

They provide food for birds, bats and small mammals; they pollinate around 75% of the crops in the world; they replenish soils and keep pest numbers in check.

Many other studies in recent years have shown that individual species of insects, such as bees, have suffered huge declines, particularly in developed economies.

But this new paper takes a broader look.

Published in the journal Biological Conservation, it reviews 73 existing studies from around the world published over the past13 years.

The researchers found that declines in almost all regions may lead to the extinction of 40% of insects over the next few decades. One-third of insect species are classed as Endangered.

"The main factor is the loss of habitat, due to agricultural practices, urbanisation and deforestation," lead author Dr Francisco Sánchez-Bayo, from the University of Sydney, told BBC News.

"Second is the increasing use of fertilisers and pesticides in agriculture worldwide and contamination with chemical pollutants of all kinds. Thirdly, we have biological factors, such as invasive species and pathogens; and fourthly, we have climate change, particularly in tropical areas where it is known to have a big impact."

beetlesImage copyrightGETTY IMAGES
Image captionDung beetles are on the retreat according to the new review

Some of the highlights of study include the recent, rapid decline of flying insects in Germany, and the massive drop in numbers in tropical forests in Puerto Rico, linked to rising global temperatures.

Other experts say the findings are "gravely sobering".

"It's not just about bees, or even about pollination and feeding ourselves - the declines also include dung beetles that recycle waste and insects like dragonflies that start life in rivers and ponds," said Matt Shardlow from UK campaigners Buglife.

"It is becoming increasingly obvious our planet's ecology is breaking and there is a need for an intense and global effort to halt and reverse these dreadful trends. Allowing the slow eradication of insect life to continue is not a rational option."

Pests on the rise

The authors are concerned about the impact of insect decline up along the food chain. With many species of birds, reptiles and fish depending on insects as their main food source, it's likely that these species may also be wiped out as a result.

cockroachImage copyrightGETTY IMAGES
Image captionCockroaches and houseflies may thrive while others decline, say experts

While some of our most important insect species are in retreat, the review also finds that a small number of species are likely to be able to adapt to changing conditions and do well.

"Fast-breeding pest insects will probably thrive because of the warmer conditions, because many of their natural enemies, which breed more slowly, will disappear, " said Prof Dave Goulson from the University of Sussex who was not involved in the review.

"It's quite plausible that we might end up with plagues of small numbers of pest insects, but we will lose all the wonderful ones that we want, like bees and hoverflies and butterflies and dung beetles that do a great job of disposing of animal waste."

Prof Goulson said that some tough, adaptable, generalist species - like houseflies and cockroaches - seem to be able to live comfortably in a human-made environment and have evolved resistance to pesticides.

He added that while the overall message was alarming, there were things that people could do, such as making their gardens more insect friendly, not using pesticides and buying organic food.

More research is also badly needed as 99% of the evidence for insect decline comes from Europe and North America with almost nothing from Africa or South America.

Ultimately, if huge numbers of insects disappear, they will be replaced but it will take a long, long time.

"If you look at what happened in the major extinctions of the past, they spawned massive adaptive radiations where the few species that made it through adapted and occupied all the available niches and evolved into new species," Prof Goulson told BBC New

"So give it a million years and I've no doubt there will be a whole diversity of new creatures that will have popped up to replace the ones wiped out in the 20th and 21st centuries.

"Not much consolation for our children, I'm afraid."




The Guardian view on the mass death of insects: this threatens us all

Global warming and industrialised farming are damaging vital ecosystems
Honey bees
 Honeybees. ‘Biodiversity is not an optional extra. It is the web that holds all life, including human life.’ Photograph: Carolyn Kaster/AP

One of the classic science-fiction treatments of the end of civilisation was The Death of Grass, by John Christopher, in which a mysterious sickness struck down all the grasses on which most of the world’s agriculture is based, from rice to wheat. In the end, politics among the survivors of plague, war and famine was reduced to a bitter fratricidal struggle over a defensible potato patch. Like most of the so-called “cosy catastrophe” novels, this could be criticised for optimism. Grim though a future of famine and the war of all against all might seem, the consequences were largely confined to humans.

The threatened extinction of insect populations around the world raises the prospect of a much more general catastrophe, which would implicate plants, birds, fish, small mammals, and everything else that depends on insects. That’s just the start. Other species, and we ourselves, depend on the animals and plants that need insects. When they go, we go. This is not just a greater catastrophe. It’s a much more plausible one. The most recent study concluded that insect biomass is decreasing around the world at a rate of 2.5% a year. At that rate, half the insects in the world will be gone in 50 years’ time, and all of them in a century – although no one will be keeping track of centuries then.

The chief driver of this catastrophe is unchecked human greed. For all our individual and even collective cleverness, we behave as a species with as little foresight as a colony of nematode worms that will consume everything it can reach until all is gone and it dies off naturally. The challenge of behaving more intelligently than creatures that have no brain at all will not be easy. But unlike the nematodes, we know what to do. The UN convention on biodiversity was signed in 1992, alongside the convention on climate change. Giving it the strength to curb our appetites is now urgent. Biodiversity is not an optional extra. It is the web that holds all life, including human life.

The two main expressions of greed that hasten this apocalypse are global warming and industrial agriculture. It appears that most of the damage is being done in the developed world by farming practices. The use of giant fields, devoid of shelter for insects of any sort at all, whether they are harmful to human interests or not, and where the plants are drenched in long-lasting pesticides, has been fatal for uncounted billions of insects. The effects of this kind of farming reach beyond the fields immediately affected, too. There has been a huge loss of aquatic insect species from the rivers into which the products of industrial agriculture are flushed by rain. Even in German nature reserves, which are by definition protected from the use of pesticides, there have been steep falls in insect populations because so many of the most widely used ones are persistent and prevent breeding. In the tropics, the steady rise of global temperatures is already devastating whole ecosystems, starting at the bottom with the insects. Last year we learned of the disappearance of almost all the ground-dwelling insects from a rainforest in Puerto Rico, and three-quarters of the species of the canopy.

Some governments have done some necessary things. The EU has banned neonicotinoid pesticides. But the necessary change also relies on individual action. As individuals we must consume less in every way, which helps with climate change. We must also change our food habits. To eat less meat and more organic is not just piety. A little self-restraint in this generation will make all the difference to our grandchildren.


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