Bees are a major source of fertilization for many plant species. No bees = no pollination = no fruit / seeds = no new plants / food for other species = when plants that rely on this process to reproduce themselves die off they won't be replaced = a world without most of our food source plants = .......... You get the picture!!
And this threat to the world's bee populations is being caused by insecticides that we human beings have developed in an effort to control other undesirable (to us) elements in our natural environment.
The two primary culprits are the neurotoxic type pesticides neonicotinoids and fipronil. These pesticides were introduced in the 1990's to replace older chemicals like DDT which had been proven to have long term harmful effects. The irony is that research now indicates these replacement chemicals are posing a similar threat to nature although manufacturers continue to claim otherwise (of course).
The insecticides are also designed to be systemic which basically means that when they're sprayed onto a plant or come into contact with it, the plant absorbs them and so every part becomes toxic to insects. Amongst the primary victims are bees but there are a number of other beneficial species also affected according to scientists.
Neonicotinoids, which are a nicotine based product, were developed in the 1980's and released onto the market in the early 1990s as a replacement for older, 'proven to be harmful' chemicals like DDT. Originally thought to be harmless or to have a low toxicity to many insect species, neonicotinoids have now been linked to a dramatic rise in bee deaths in hives located in close proximity to crops and other food sources where neonicotinoid based pesticides have been used. This is due to the fact that traces of the pesticides have been found in dead bees in these areas and it is now suspected that toxicity levels of the pesticide for bees and other beneficial insects is much lower than previously thought. It is also believed that exposure to these chemicals is occurring in hitherto unsuspected ways via dust, pollen and nectar.
Other testing and research is also showing traces of neonicotinoid pesticide contamination and residues in water ie irrigation channels, and in soil samples up to two years after treated seeds have been planted. Aerial dispersal of the chemicals from treated seeds also occurs because seeds treated with the insecticide are covered with a sticky substance to control their release but are then coated with talc for machine planting (because obviously being sticky the seeds would adhere to the machines if they weren't dusted with something to prevent that). A significant amount of this talc (referred to as exhausted talc) is thought to get released into the environment during the seeding process and when it lands on flowers whose pollen is collected by bees.... Testing of this talc has shown it can contain around 700,000 times the lethal dose required to kill a bee!!
Researches in Italy have also demonstrated that neonicotinoids affect the immune system of bees which makes them susceptible to viral infections that they are usually resistant to.
The other culprit is Fipronil which is extremely toxic to marine life (fish and other aquatic invertebrates). It is however not particularly water soluble and tends to bind to sediments rather than get dissolved into the water so this may reduce its potential effect in the marine environment. Fipronil has always been known to be toxic to bees so its use in areas where bees live and forage has always been cautioned against but probably with limited effect unfortunately.
Interestingly Fipronil is also toxic to some species of birds, notably upland game birds but has no effect on waterfowl and other similar species. Apparently there is a metabolite within the pesticide rather than the parent compound of the pesticide itself that is toxic to some bird species.
One of the primary uses of Fipronil that we are most familiar with is as the active compound in many popular flea control pet products. It is also used on golf courses and commercial turf farms to control fleas. However, genetic resistance is now becoming an issue as flea populations develop resistance to it.
The issues with both these groups of pesticides doesn't just end there though. As mentioned above there is now enough research available to indicate that they accumulate in the soil and leach into water which means that they are a significant threat to many other beneficial species which live in those environments such as earthworms, freshwater snails, butterflies and birds.
There are also serious implications for food chains in general as the presence of higher levels of neonicotinoids in water environments affects the species that live there which in turn effects the species that depend on aquatic invertebrates for food (wading birds, fish etc).
Several governments around the world have put moratoriums on their use pending further research into the cumulative effects on the environment and in particular their deleterious effects on bee populations. Their use on certain types of crops has also been banned outright in one or two countries. Yet manufacturers of the chemicals continue to claim that there is no real hard scientific evidence to back up any of the above issues!! Hmm, reminds one of the tobacco companies who also claim there is no evidence to support the 'theory' that smoking causes cancer....
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