Bees: essential pollinators whose health is under threat

Bees, sentinels of ecosystem health

Bees and other pollinating insects are essential to the fertilisation of many plants, and to fruit production in particular. Ninety per cent of flowering plant species depend solely on insect pollinators for their reproduction. This makes them true sentinels of ecosystem health and the maintenance of biodiversity. Seventy-five per cent of the world's food crop production depends in part on the action of pollinators. These include some 20,000 species of bees, of which around 850 are found in France. 

Excess bee colony mortality, a complex phenomenon with multiple causes

Bee mortality is a normal phenomenon in apiaries. Every winter, 5 to 10% of colonies die, and during the breeding season (February/March to September/October), many forager bees die every day. However, since the mid-1980s, the phenomenon of excess bee colony mortality has been observed worldwide. As part of its expert appraisal and research work, ANSES highlighted the multifactorial nature of bee colony collapse. This is a complex phenomenon involving many factors likely to interact during concomitant or successive exposure. 

Five main categories of causes:

• Biological causes
  So far, 29 agents threatening bees have been counted: predators, parasites, fungi, bacteria and viruses. All these predators and pathogens are potentially involved in the weakening and loss of bee colonies, and some may act simultaneously.
   
• Depletion of food sources
  To meet their needs, bees must have high-quality pollen from diverse flora (a source of protein) and nectar to produce the honey (a source of energy) they store during the beekeeping season. These food resources are not all of equivalent quality: indeed, bees tend to favour certain pollens that are richer in nutrients. The loss of biodiversity, largely due to monoculture, has resulted in a reduction in the number of plant species available and a shortening of the season during which many nectar-producing flowering plants are available. The shortage of pollen, the lack of sufficient reserves, and the absence of diversity or quality in these inputs can all have an adverse effect on bee colony health. 
   
• Beekeeping practices 
  How the apiary is managed determines its state of health, so it is essential that the beekeeper pays close attention to factors that are critical to the successful development of colonies. Compliance with technical rules and biosafety in terms of living environment, swarming, feeding, etc. is essential to the health of the apiary. It is also important to carry out regular checks and ensure that treatments against disease are used appropriately.  
   
• Exposure to chemicals used in the environment
  Like all living organisms, bees can be exposed to a variety of chemical agents likely to be found in the environment. In cultivated areas, most of these chemicals belong to the category of plant protection products. The bees are exposed directly when treatments are applied, but also through pesticide residues in the pollen and nectar they collect. 
   
• Causes that are still unknown and effects that are difficult to demonstrate
  In the absence of any aetiological diagnosis, the cause of many cases of mortality remains undetermined to date. A wide variety of factors, acting either alone or in combination, may therefore cause abnormal mortality in bee colonies. Some of these factors are now well known and regularly identified (this is the case with many biological and chemical agents). However, for others, it is difficult to demonstrate their effect (effect of the nutrient environment, of climatic factors, of certain plant protection products or viral infections, etc.). In addition, the combined effect of several of these is still unclear, despite ongoing studies.

What the expert say

"The phenomenon of bee mortality is multifactorial, which makes it all the more difficult to study and prevent."

Interview with Gilles Salvat,
Managing Director General of the Research and Reference Division.

"The problem is that bees live in an open environment. Their diet is linked to many factors. So the issue is not just the availability of their food in the environment, but also the ability of the bees to gather the available resources and alert their fellow bees to their existence.

Another problem is that bees are difficult animals to treat, because they cannot be isolated. And to avoid leaving any trace of drugs in honey, only a few parasitic treatments to combat varroa mites, for example, are allowed. The varroa mite alone can be fatal to bees. Co-exposure to other stress factors, such as pesticides and nutritional deficiencies, weakens their defence systems and makes them even more vulnerable to infestation by the parasite. These factors have worsened over the last 20-25 years.

To improve bee health, it is vital to prevent and treat diseases more effectively, but also to reduce the use of plant protection inputs. This means turning to other methods of cultivation, not only in the fields but also in our gardens and public parks."

Reference laboratory for bee health in France and Europe 

Over more than 40 years, ANSES's Sophia-Antipolis Laboratory has become a national and international reference in bee health. It holds the mandates of National Reference Laboratory and European Union Reference Laboratory for bee health, as well as World Organisation for Animal Health (WOAH) Reference Laboratory for six bee diseases. The teams study bee diseases, the bacteria, parasites or viruses that cause them, and the effects of plant protection products. They develop analytical methods to detect and identify the pathogens and product residues that are most hazardous to bee health. The laboratory's work has led to major advances in understanding the many factors behind the problems affecting bee colonies, and in implementing sustainable solutions for their preservation at national and European level.

As part of its European reference mandate, ANSES’s Sophia-Antipolis Laboratory has been leading EPILOBEE, a vast epidemiological surveillance programme in Europe that is aiming to better characterise the phenomenon of excess bee mortality.

It has also taken part in various other European projects such as:

• the SmartBees project, which ended in 2018, focused on the natural resistance of bees to a major parasitic mite (Varroa destructor) and to viruses transmitted by this parasite.
• the PoshBee project, to develop a comprehensive approach to determining the disorders affecting honeybees and wild bees. It ended in 2023. Read our news item on the results of the PoshBee project.

Insights into the effects of co-exposure

ANSES has undertaken several expert appraisals since 2012 to understand the multiple causes of colony collapse. Its work shows a complex reality of interactions between pathogens such as the varroa mite and certain viruses, or between chemicals. Some of them, for example, reduce the bees' immune defences, making them more vulnerable to pathogens. These factors are compounded by the loss of biodiversity, particularly regarding the bees' preferred flowers, and by climate change, which diminish their food resources.

In view of this finding, ANSES has recommended several avenues of work to be explored, such as the development of more refined multi-residue measurements of specimens and hive products to better identify the compounds found in the bee's environment. It has also developed identification and quantification methods with very low thresholds for the many compounds from different chemical classes used in pesticides. The Agency also recommended creating a network of reference apiaries to better analyse the situation of apiaries in the different regions. Lastly, ANSES also recommended an overall reduction in the use of chemical inputs and stricter requirements for marketing authorisations.

Developing the assessment of risks of plant protection products to the environment, and to bees in particular

In order to reduce the exposure of bees and other pollinating insects to plant protection products, ANSES has assessed different national provisions and made various recommendations to change the restrictions at national level and the assessment of products at European level.

ANSES's recommendations on strengthening protection of bees exposed to plant protection products:

• In addition to the systematic assessment of acute and chronic risks to adult bees and larval development as part of marketing authorisation (MA) applications, ANSES recommended conducting new tests, as soon as the necessary methods become available.
• ANSES also recommended not applying any plant protection products when bees are present during crop flowering periods.
• It recommended compensatory measures to improve the protection of pollinators in cases where plant protection treatments during flowering periods are essential.
• With regard to MA applications, it proposed improving methods for assessing long-term risks to bees and other pollinators, including the introduction of tests on bee behaviour, such as the method of measuring the time taken to return to the hive, once standardised protocols are available.