Echoes of the disappeared
Are we in for another Silent Spring?
Something is very rotten in England’s green and pleasant land. During the past four years, some 40,000 amateur British bird-watchers ticked 20 million records of almost 300 species to help inform the British Trust for Ornithology’s periodic tome, the Bird Atlas—the de facto state of the ornithological nation. The twitchers signed off some bad news. By 2025, many of Britain’s birds will be gone, and not only rare ones. They’re talking also about town and country icons: sparrows, starlings, skylarks (750,000 pairs lost since 1986).
This seems inconceivable, but things are worse still: whatever’s killing these familiar feathered friends is mowing them down across Europe, too. Late last year, a team of British and Czech researchers concluded that more than 421 million birds across 25 European countries had vanished since the early 1980s—a 20 per cent loss of bird biomass.
Some 90 per cent of that decline, said the study, was suffered by the 36 most common species. As in Britain, it was house and tree sparrows, starlings, skylarks and willow warblers that were taking the biggest hammering. “Common species are widespread and their numbers are linked to the deterioration of the quality of the environment on a landscape scale,” the report concluded. Some people blamed habitat loss: increasing urbanisation and the continued felling of woodlands for agriculture have simply given many species nowhere to go.
But others are blaming pesticides. Neonicotinoids—neonics for short—were touted as a more environmentally benign way to deal with insects that were damaging crops. They are now the most widely used insecticides on the planet, with sales of more than $3 billion annually. In much the same way as nicotine affects humans, neonics act on the insect’s nervous system, and manufacturers claim they do not harm non-target phyla as did scourges of the 60s and 70s such as DDT. With neonicotinoids, biochemists get plants to do their own pest control: the chemicals are water-soluble, so that crop plants can take them up into their leaves, stems and roots. A stalk of maize becomes an insecticide factory, oozing poison from every pore.
Lately, chemical companies have developed a way to apply neonics to seeds, so that plants don’t even need to be sprayed. They’re toxic from the first sprout. Imidacloprid is one such new-generation pesticide, and recently,
When Dutch scientists placed historic bird abundance records over a map of surface water contaminated with imidacloprid, they drew a straight line between it and bird collapse.
“If the concentrations are higher than 20 nanograms per litre in the environment, we found a reduction of 3.5 per cent in local populations,” said Dr Hans de Kroon from Radboud University. “In 10 years, it’s a 35 per cent reduction in the local population. It’s really huge.” The pathway, they suggest, is imidacloprid leaching into soil and water, where it persists and accumulates, sometimes for two or three years. That build-up, they claim, is killing more than just crop pests; it’s killing the insects that birds rely on for food, too. “It might increase their mortality by food deprivation. We think this is the most likely mechanism.” However, it’s also possible that seed-eaters such as sparrows are ingesting imidacloprid directly.
Manufacturer Bayer rejects the findings of the study, but evidence appears to be mounting. For years, people have also blamed the new-generation insecticides for the widespread disappearance of honeybees. Since 2000, plantings of rapeseed in England and Wales have more than doubled to 602,270 hectares, and more than three-quarters of those crops are now derived from imidacloprid-infused seeds. Scientists of the Food and Environment Research Agency (Fera) in York plotted honeybee declines against the use of imidacloprid and found another alarming correlation.
It is impossible to estimate the value of honeybees: they pollinate at least 90 per cent of global commercial crops and are the most frequent visitors to rapeseed flowers. “As long as acute toxins remain the basis of agricultural pest-control practices, society will be forced to weigh the benefits of pesticides against their collateral damage,” said the Fera team. “Nowhere is this tension more evident than in the system with the world’s most widely used insecticide, the world’s most widely used managed pollinator and Europe’s most widely grown mass flowering crop.”
Colony collapse disorder is the name of that “tension”, a euphemism for millions of worker bees leaving their hives, never to return. This mass disappearance has led to a 30 per cent decimation of hives in the United States and up to a half of all European hives. Neonicotinoids have been used in New Zealand for some 20 years, mostly as a pre- treatment solution on maize, cereal, pasture grass and brassica seeds.
Common label names are Cruiser (thiamethoxam), Gaucho (imidacloprid) and Poncho (clothianidin). The agricultural lobby is quick to point out that we have yet to see the same level of hive destruction here, though many losses are not investigated, and effects may be masked by the relatively recent arrival of the Varroa mite. For their part, chemical companies have set formulations to fall below the known lethal dose to bees, but more and more studies are finding evidence of sub-lethal effects. Last year, a review of some 800 peer- reviewed papers found conclusive evidence that neonics are causing significant damage to earthworms, butterflies, bees and birds without necessarily killing them outright.
Earthworms had trouble tunnelling.
Butterflies didn’t breed, and honeybees lost their sense of smell and/or memory, and had trouble flying. Suddenly, it became clear why they weren’t making it back to their hives. Such findings prompted a two-year restriction across Europe, starting in December 2013. In New Zealand, the Environmental Protection Authority (EPA) says current regulations are working: neonics are not to be sprayed on budding or flowering plants or near beehives. In practice, it’s difficult to see how that works—bees forage far and wide, making trips of two kilometres or more. That’s been borne out with the discovery of imidacloprid residues in pollen samples from kiwifruit that were never treated.
Neonics, like their infamous organophosphate predecessors, would seem to be highly mobile, too: the Harvard School of Public Health in Boston has found residues in fruits, vegetables and pollen sampled from both the United States and New Zealand. “Far from protecting food production,” said the leader of the 2014 literature review, Dr Jean-Marc Bonmatin, “the use of neonics is threatening the very infrastructure which enables it, imperilling the pollinators, habitat engineers and natural pest controllers at the heart of a functioning ecosystem.”
According to the International Union for Conservation of Nature, Europe’s wild bee populations are in freefall, and more than a quarter of species— even the ubiquitous bumblebee—are at risk of extinction.
There is undoubtedly more than to this than pesticides alone, but people are already comparing neonics to DDT, a persistent carcinogenic pesticide that was finally only banned in the US after publication of Rachel Carson’s iconoclastic book, Silent Spring, in 1962. The EPA insists that, should new research give it cause, neonics could be reassessed with a view to tighter regulation or an outright ban. If so, we would need to move faster than we did on endosulfan, a notorious organophosphate insecticide that was banned in 55 countries before it was finally outlawed here in 2008, and then only because Korea had rejected export beef that tested positive for endosulfan residues.
There’s been occasional talk of repopulating Britain with skylarks and bumblebees from New Zealand—an ecological irony. The way things are going, they may need some of our starlings, song thrushes and sparrows, too—assuming they don’t succumb here as well.