The Causes

“Pollinators cannot escape the various and
massive impacts of industrial agriculture”

Insecticides in particular pose the most direct risk to pollinators

As their name indicates, these are chemicals designed to kill insects, and they are widely applied in the environment, mostly around cropland areas.

The main reasons for global bees-decline are industrial agriculture, parasites/pathogens and climate change. The loss of biodiversity, destruction of habitat and lack of forage due to monocultures and bee-killing pesticides are particular threats for honeybees and wild pollinators. It is becoming increasingly evident that some insecticides, at concentrations applied routinely in the current chemical-intensive agriculture system, exert clear, negative effects on the health of pollinators – both individually and at the colony level. The observed, sub-lethal, low-dose effects of insecticides on bees are various and diverse.

1. Physiological effects

…which occur at multiple levels, and have been measured in terms of developmental rate (i.e. the time required to reach adulthood), and malformation rates (i.e. in the cells inside the hive), for example.

2. Perturbation of the foraging pattern

…for example through apparent effects on navigation and learning behaviour.

3. Interference with feeding behaviour

…through repellent, antifeedant, or reduced olfactory capacity effects.

4. Impacts of neurotoxic pesticides on learning processes

…(i.e. flower and nest recognition, spatial orientation), which are very relevant and have been studied and largely identified in bee species.

Agriculture, in both croplands and pastures, occupies about 35% of the ice-free land surface
on Earth, and is one of the largest ecosystems on the planet, rivalling forests in extent.

Destructive industrial agriculture

The negative effects of chemical-intensive agriculture become more and more apparent.

The global bees-decline is just a symptom of a failed industrial agricultural system based on ever increasing chemical and energy inputs, large-scale monoculture and dependency from few multinational agri-companies. Growing pest and weed resistance, decreasing soil fertility, widespread water contamination, increasing CO2 emissions and vulnerability to climate change, as well as a systemic loss of resilience, diversity and sovereignty in the global food production press us to make the transformational change towards biodiversity based ecological farming systems.

Bee-killing pesticides

Finally, widespread and ubiquitous use of pesticides, common practice in the current chemical intensive agriculture systems, can lead to mortality and/or altered foraging abilities for both wild and managed bees.

Determining the specific role of pesticides in pollinator health is further complicated because sites where pesticide use is intense often also correspond with places with low availability of both flower resources and nesting sites (important for many wild pollinators) (Kremen et al, 2007).

More details in the Report «Bees In Decline»

Intensification of agriculture

Intensification of agriculture prompts the loss and fragmentation of valuable natural to semi-natural perennial habitats for pollinators, such as agroforestry systems, grasslands, old fields, shrublands, forests, and hedgerows.

This is thought to be the major cause of wild pollinator declines, although with smaller effects on managed honeybees (Brown and Paxton, 2009; Winfree et al, 2009).

More details in the Report «Bees In Decline»


Industrial monocultures are not natural and only sustained with the application of high amounts of fertilisers, pesticides and heavy machinery. Monocultures result in a lack of biodiversity (genetic diversity and diversity of plants and landscapes) within and around croplands, and limit the amount of food that pollinators have access to, both in space and time.

A parallel decline in plant diversity at the local scale with the decline in bees and other pollinators has been shown both in the UK and the Netherlands (Biesmeijer et al, 2006), and it is possibly a much more widespread phenomenon.

More details in the Report «Bees In Decline»

Industrial practices

Practices such as tillage, irrigation, and the removal of woody vegetation, destroy nesting sites of pollinators (Kremen et al, 2007).

More details in the Report «Bees In Decline»

Parasites and Pathogens

In several countries, parasites like the Varroa mite have been identified as a major cause of bee colony loss. Agro-chemical companies like Bayer, Syngenta and BASF claim that industrial agriculture and pesticides, including neonicotinoids, play an almost negligible role in bee death. However, several studies show that pesticides undermine the immune system of insects, making them more susceptible to disease, parasites and pathogens.

There is growing evidence that exposure to pesticides may compromise the immune system of bees. Furthermore, there is also evidence that exposure to pesticides may increase the susceptibility of bees to infections with parasites. Alaux et al. (2010) showed that the combined effects of imidacloprid and parasite infestation significantly weakened honeybees, causing high mortality and high levels of stress, blocking the ability of bees to sterilise the colony and their food, and thus weakening the colony as a whole.


More details in the Report «Bees In Decline»

Herbicide application

Large-scale herbicide application drastically reduces noncrop plant diversity and abundance, and thus limits food availability for bees at any given moment.

The chemical destruction of habitats through the massive application of herbicides can have long term consequences, particularly on the distribution of pollinators in agro-environments (UNEP, 2010).

More details in the Report «Bees In Decline»

Climate change

Many of the predicted consequences of climate change, such as increasing temperatures, changes in rainfall patterns, and more erratic or extreme weather events, will have impacts on pollinator populations.

Such changes might affect pollinators individually and ultimately their communities, reflected in higher extinction rates of pollinator species (UNEP, 2010).

More details in the Report «Bees In Decline»

"Herbicides have also been found to increase the toxicity of a number of insecticides
in flies and mice, but this has not been documented for bees. A sub-lethal impact of
an insecticide that reduces bees’ foraging efficiency may have more damaging
consequences for its health if the bees are exposed at a time when
its food resources have been reduced by the application of herbicides."

− Brittain and Potts 2011

"Pollinators are being increasingly exposed to a cocktail of pesticides, for instance
up to 17 different pesticides detected in just one sample of pollen from a honeybee
colony (Frazier et al, 2008); and this has unknown consequences for bee health
and pollination services. Given the prediction of increasing global pesticide production
(Tilman et al, 2001) and cultivation of pollinator dependant crops (Aizen et al, 2008),
this issue is likely to increase in importance in the future."

− Brittain and Potts 2011

"Potential for interactions among multiple pyrethroids and fungicides seems
highly likely to impact bee health in ways yet to be determined."

− Mullin et al 2010

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