The little things that run our world
FOR the last five or so years, I have noticed that I have not had to clean dead insects off my car windscreen or headlights after driving on motorways. Perhaps my recent car is more aerodynamic but I hardly think so. Over the last few decades, there has been a worldwide decline in the flying insect population. Hoorah, we may say in Borneo, if this has led to the demise of mosquitos and I, for one, will join in the chorus!
Recently, a group of dedicated, amateur German entomologists revealed their findings from tracking flying insects in over 100 nature reserves in Western Europe since the 1980s. This group, the Krefeld Entomological Society (KES), in 2014, spotted an alarming change in their trapped insect populations.
Certainly, insect populations fluctuate from year to year depending upon the number of predators and fluctuations in weather patterns but upon returning to one of their earliest trapping sites of 1989, they found that that the total mass of their catch had fallen by 80 per cent. This decline was again seen in many more sites.
KES members have been observing, recording and collecting insects since the society’s foundation in 1905. Krefeld, an industrial town in the German state of North Rhine-Westphalia, was once famous for its silk manufacture. This society’s headquarters, now located in a disused school, houses an interesting and vast collection of insects to include exotic species. In the late 1940s and early 1950s, a member of the society, a local priest, persuaded fellow priests in mission stations worldwide to send him specimens. I just wonder, how many Bornean insect specimens reside there?
In their findings, the KES found that the average biomass of insects trapped, between May and October, steadily decreased from 1.6kg per insect trap in 1989 to just 300 grams in 2014. This decline affected all kinds of insects, to include butterflies, hoverflies and wild bees – all valuable pollinators of flowers. Fall in insect populations In 2014, Zoologists at Stanford University, USA, developed a global index for invertebrate abundance which revealed a 45 percent decline over the last forty years. On the International Union for Conservation of Nature Red List, 42 per cent of some 3,623 known terrestrial invertebrates are threatened with extinction.
The Zoological Society of London, earlier in its 2012 publication ‘Major survey of threats to insect life’, noted that many insect populations globally were in severe decline and thus limiting food supplies for larger animals and affecting the ecosystem services of pollinators. In both Europe and the USA, declines in wild bee and managed bee populations have been between 30 and 40 per cent owing to colony collapse disorders. One of the longest distance migrating insects, the Monarch butterfly has also shown a marked fall in population. Causes of decline Many factors have been cited, varying from the worldwide use of pesticides and the spread of monoculture crops, such as corn, soya beans and palm oil, to rapid urbanisation and habitat destruction. A fall in insect populations has far reaching consequences not only in the natural world but also for humans, for the latter depend upon bees and other flying insects to pollinate crops.
Interestingly, Canadian zoologists have suggested that native North American and European bird species, such as larks, swallows and swifts, which depend on flying insects for food, have suffered a more pronounced decline than other perching birds that feed off seeds. Poisoning of landscapes In the UK, it has been calculated that 75 per cent of wild flowering plant species need pollination by flying insects to fully develop their fruits and seeds. Actually, pollinating insects increase the yield of all crop types globally. Not only are insects a major food source for birds but also for bats and amphibians. Some flying insects prey upon other insect pests.
In large swathes of our world, monoculture agricultural practices have created ‘biological deserts’ without hedges and ponds in which insects can reproduce. The widespread use of nitrogenous fertilisers certainly allows grain crops to thrive at the expense of the majority of plant species which depend upon a symbiotic relationship with specialised insects.
The removal of wildflower meadows where numerous varieties of native grasses were once seen and their replacement by Italian rye grass species – fast growing and highly nutritious grasses for cattle and sheep grazing – has also led to the fall in insect populations. Such new grasslands are regularly fertilised with nitrogenous sprays.
This summer, in the UK, I have only seen a few Mayflies or ‘Daddy longlegs’ and houseflies, fewer butterflies and ladybirds and other flying insects in the fields around my house, which are now devoted to lowland sheep grazing and cattle fodder maize crops. The buzzing of bees in these fields are now noises from yesteryear but thankfully are still heard on the bushes and flowers in my garden.
The widespread use of pesticides has had a drastic impact on non-target species of insect. Relatively new but increasingly used pesticides – neonicotinoids – are the prime suspects for insect loss. For many years these were used throughout Europe until a recent temporary ban. It is thought that these pesticides reduce the mating instincts of insects and affect their abilities to navigate and communicate. Just four billionths of a gram of this chemical is enough to paralyse and kill a bee!
The European Union’s Common Agricultural Policy has significantly contributed to the decline in insect populations through subsidies paid to farmers for more extensive and machine intensive farming, especially the growing of oilseed rape, maize and wheat. Farmers receive no subsidies for enriching their landscapes with hedgerows or for organic farming practices without the use of chemical fertilisers and pesticides. No rewards are accorded such farmers but increasing consumer purchases in shops of organically grown vegetables may soon change this.
The future of our global insect populations hangs precariously in the balance and depends much upon governmental policies on biodiversity.
We depend on insects as much as they depend on us and we may well ask ourselves, where have all the insects gone?