Arxiu d'etiquetes: Wild bees

How would it be a world without bees?

In recent years, the idea of a world without bees has transcended numerous social and political spheres. The scientific community has been warning about the disappearance of bees during years without any consequence. But now, it has become an issue of major concern, acquiring a media relevance like never before. At the end of 2017, the EU decided to take matters into its own hands to prevent this tragic ending for bees.

Why would it be a problem that bees disappear from Earth? And which measures has the UE take in order to address this problem?

The DDT and Rachel Carson

The use of pesticides has been a common agricultural practice from the very beginning of agriculture. At the beginning, the use of organic chemicals derived from naturals sources, as well as inorganic substances such as sulphur, mercury and arsenical compounds, was very common. However, they eventually stopped being used due to their toxicity (especially, phytotoxicity). The growth in synthetic pesticides accelerated in the mid-twentieth century, especially with the discovery of the effects of DDT, which became one of the most widely used pesticides of all time. DDT became famous due to its generalist insecticidal effects and low toxicity to mammals and plants, being used to eradicate household pests, fumigate gardens and control agricultural pests.

Picture above: cover of a March 1947 brochure on DDT from the U.S. Department of Agriculture (source). Picture below: kids being showered with DDT during a campaing against poliomyelitis, which was believed to be transmitted by a mosquito (source).

DDT resulted to be very effective against insect vectors of deadly diseases such as malaria, yellow fever and typhus, thus becoming even more popular.

However, the overuse of this and other pesticides eventually began to cause severe human and environmental health problems, because some of these products started to contaminate soils, plants and their seeds, and to bioaccumulate within the trophic nets, finally affecting mammals, birds and fishes, among others. The indiscriminate use of pesticides and their effects were denounced by Rachel Carson through her most famous publication, “Silent Spring”, which was distributed in 1962.

Silent Spring, by Rachel Carson (source).

From Carson to the neonicotinoids

Since Carson denounced the abusive use of pesticides, the world has witnessed the birth of many new substances to fight crop pests. Since then, researches have focused on finding less toxic and more selective products in order to minimize their impact on both human and environmental health. Could we say it has been a success?

Yes… and no. Although their use stopped being so indiscriminate and famers started betting on the use of more selective products, there were still some open fronts. Fronts that would remain open until today.

Between 1980 and 1990, Shell and Bayer companies started working on the synthesis of a new assortment of pesticides to face the resistances that some insects have acquired to some of the most widely used substances those days: the neonicotinoids. Neonicotinoids are a class of neuro-active insecticides chemically similar to nicotine; they effect the insect nervous system with a high specificity, while having a very low toxicity to mammals and birds compared to their most famous predecessors (organochlorides, such as the DDT, and carbamates). The most widely used neonicotinoid nowadays (and also one of the most widely used pesticides worldwide) is the imidacloprid.

However, far from getting famous for their effectiveness, the use of neonicotinoids began to get controversial for their supposed relationship with the disappearance of bees.

How do these pesticides affect bees?

For some years now (2006 onwards) the neonicotinoids are in scientists’ spotlight as one of the main suspects of the disappearance of bees. However, it has not been until now that something that scientists had been denouncing for years has finally been assumed: that neonicotinoids cause a greater impact than it was thought.

Dead bees in front of a hive. Public domain.

Unlike other pesticides that remain on plant surfaces, some studies state that neonicotinoids are taken up throughout their tissues, thus being accumulated in their roots, leaves, flowers, pollen and nectar. Also, that nearby fields are polluted with the dust created when treated seeds are planted and that plants derived from these seeds will accumulate a major amount of pesticide than sprayed plants (as it is explained in this publication of Nature). This causes bees (as well as other pollinating insects) to be exposed to high levels of pesticides, both in the crops themselves and in the surrounding foraging areas. These same studies have revealed with less support that these products may persist and accumulate in soils, which may affect future generations of crops.

Some of the negative effects on bees that have been related to neonicotinoids are:

In addition to the effects of neonicotinoids, other important causes must be taken into account: climate change, less food sources and changes in soil uses.

What would happen if bees disappear?

Colonial bees (like honeybees) are the most famous among bees. However, they only represent a mere portion within the great diversity of known bees, most of which have solitary life habits and build their nests inside small cavities. The ecological importance of solitary bees is equal to or greater than that of honey bees, but effects that neonicotinoids have on them are still poorly studied. Together, bees are among the most efficient pollinating organisms.

Solitary bee entering in its nest. Public domain.

According to this study carried out in German territory and published in POLS One at the end of 2017, a large part of flying insect diversity (including numerous pollinators) and up to 75% of their biomass have decreased in the last three decades due to the interaction of several factors. And if that was not enough, the authors say that these numbers can probably be extrapolated to other parts of the world.

What would happen if both colonial and solitary bees disappear?

  • Disappearance of crops. The production of many crops, such as fruit trees, nuts, spices and some oils, depends entirely on pollinators, especially on bees.
  • Decrease in the diversity and biomass of wild plants. Up to 80% of wild plants depend on insect pollination to reproduce, as it happens with many aromatic plants. A decrease in the vegetal surface would lead to serious problems of erosion and desertification.
  • Less recycling of soil nutrients. With the disappearance of the plants, the washing and deposition of soil nutrients would go down.
  • Less biological pest control. Some solitary bees are parasitoids of other solitary bees and other groups of insects (natural enemies); their absence could trigger the recurrence of certain pests.
  • Negative effects on higher trophic levels. The disappearance of bees could cause a decrease in the diversity and biomass of some birds that feed on pollinators.
  • Disappearance of bee-derived products, such as honey or wax.

The UE bans the use of neonicotinoids

Facing this reality, several governments have tried to limit the use of pesticides as a part of the measures to stop the decline of bee populations and the resulting economic losses. To give some examples, since 2006 the biomass of honey bees has decreased by 40% in the US, 25% in Europe since 1985 and 45% in the United Kingdom since 2010, according to data published by Greenpeace.

To date, the more restrictive measures limited the use of neonicotinoids in certain situations or seasons. But at the beginning of 2018, the EU, after preparing a detailed report based on more than 1,500 scientific studies carried out by the EFSA (European Food Safety Authority), decided to definitively ban the use of the three most used neonicotinoids in a maximum period of 6 months in all its member states after demonstrating that they are harmful for bees: imidacloprid, clothianidin and thiamethoxam.

Will the objectives of this report be accomplished? We will have to wait …

.           .           .

Although slowly, the fight against the abusive use of pesticides is paying off. However, we will have to see if the gap left by some products is filled with other substances or if governments commit to adopt more environment friendly agricultural models.

Main picture obtained from [link].

Anuncis

The secret life of bees

If we talk about bees, the first thing that comes to mind might be the picture of a well-structured colony of insects flying around a honeycomb made of perfectly constructed wax cells full of honey.

But the truth is that not all bees known nowadays live in hierarchical communities and make honey. Actually, most species of bees develop into a solitary life-form unlike the classical and well-known honey bees (which are so appreciated in beekeeping).

Through this article, I’ll try to sum up the different life-forms of bees in order to shed light on this issue.

INTRODUCTION

Bees are a large diverse group of insects in Hymenoptera order, which also includes wasps and ants. To date, there are up to 20,000 species of bees known worldwide, although there could be more unidentified species. They can be found in most habitats with flowering plants located in every continent of the world (except for the Antarctica).

Bees pick up pollen and nectar from flowers to feed themselves and their larvae. Thanks to this, they contribute on boosting the pollination of plants. Thus, these insects have an enormous ecological interest because they contribute to maintain and even to enhance flowering plant biodiversity on their habitats.

Specimen of Apis mellifera or honey bee (Picture by Leo Oses on Flickr)

However, even though the way they feed and the sources of food they share could be similar, there exist different life-forms among bees which are interesting to focus on.

BEE LIFE-FORMS

SOLITARY BEES (ALSO KNOWN AS “WILD BEES”)

Most species of bees worldwide, contrary to the common knowledge, develop into a solitary life-form: they born and grow alone, they mate once when groups of male and female bees meet each other and, finally, they die alone too. Some solitary bees live in groups, but they never cooperate with each other.

Female of solitary life-form bees build a nest without the help of other bees. Normally, this kind of nest is composed by one or more cells, which are usually separated by partition walls made of different materials (clay, chewed vegetal material, cut leaves…). Then, they provide these cells with pollen and nectar (the perfect food for larvae) and, finally, they lay their eggs inside each cell (normally one per cell). Contrary to hives, these nests are often difficult to find and to identify with naked eyes because of its discreetness.

The place where solitary bees build their nest is highly variable: underground, inside twisted leaves, inside empty snail shells or even inside pre-established cavities made by human or left behind by other animals.

These bees don’t make hives nor honey, so these are probably the main reasons because of what they are less popular than honey bees (Apis mellifera). Although solitary bees are the major contributors on pollination due to their abundance and diversity (some of them are even exclusive pollinators of a unique plant species, which reveals a close relation between both organisms), most of the studies related with bees are focused on honey bees, because of what studies and protection of these solitary life-forms still remain in the background.

There exists a large diversity of solitary bees with different morphology:

3799308298_ff9fbb1bcc_n7869021238_a811f13aa4_n1) Specimen of Andrena sp. (Picture by kliton hysa on Flickr). 
2) Specimen of Xylocopa violacea or violet carpenter bee (Picture by Nora Caracci fotomie2009 on Flickr).
3) Specimen of Anthidium sp. (Picture by Rosa Gambóias on Flickr).

There are also parasite life-forms among solitary bees, that is, organisms that benefit at the expense of another organism, the host; as a result, the host is damaged in some way. Parasitic bees take advantage of other insects’ resources and even resources from other bees causing them some kind of damage. This is the case of Nomada sp. genus, whose species lay their eggs inside other bee nests (that is, their hosts), so when they hatch, parasite larvae will eat the host’s resources (usually pollen and nectar) leaving them without food. Scientists named this kind of parasitism as cleptoparasitism (literally, parasitism by theft) because parasitic larvae steal food resources from the host larvae.

PSEUDOSOCIAL BEES

From now on, we are going to stop talking about solitary bees and begin to introduce the pseudosocial life-forms, that is, bees that live in relatively organized and hierarchical groups which are less complex than truly social life-forms, also known as eusocial life-forms (which is the case of Apis mellifera).

Probably, the most famous example is the bumblebee (Bombus sp.). These bees live in colonies in which the queen or queens (also known as fertilized females) are the ones who survive through the winter. Thus, the rest of the colony dies due to cold. So is thanks to the queen (or queens) that the colony can arise again the next spring.

5979114946_9d491afd84_nSpecimen of Bombus terrestris or buff-tailed bumblebee(Picture by Le pot-ager "Je suis Charlie" on Flickr).

EUSOCIAL BEES

Finally, the most evolved bees known nowadays in terms of social structure complexity are eusocial bees or truly social bees. Scientist have identified only one case of eusocial bee: the honey bee or Apis mellifera.

Since the objective of this article was to refute the “all bees live in colonies, build hives and make honey” myth, I will not explain further than the fact these organisms form complex and hierarchical societies (this constitutes a strange phenomenon which has also been observed in thermites and ants) normally led by a single queen, build large hives formed of honeycombs made of wax, and make honey, a very energetic substance highly appreciated by humans.

Specimens of Apis mellifera on a honeycomb full of honey (Picture by Nicolas Vereecken on Flickr).

As we have been seeing, solitary bees play an important role in terms of pollination, because of what they must be more protected than they currently are. However, honeybees, and not solitary bees, still remain being on the spotlight of most scientists and a great part of society because of the direct resources they provide to humans.

REFERENCES

  • Notes taken during my college practices at CREAF (Centre de Recerca Ecològica i d’Aplicacions Forestals – Ecological Research and Forest Applications Centre). Environmental Biology degree, UAB (Universitat Autònoma de Barcelona).
  • O’toole, C. & Raw A. (1999) Bees of the world. Ed Blandford
  • Pfiffner L., Müller A. (2014) Wild bees and pollination. Research Institute of Organic Agriculture FiBL (Switzerland).
  • Solitary Bees (Hymenoptera). Royal Entomological Society: http://www.royensoc.co.uk/insect_info/what/solitary_bees.htm
  • Stevens, A. (2010) Predation, Herbivory, and Parasitism. Nature Education Knowledge 3(10):36

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