Threats to and the Consequences of the Disappearance of Wild Bees

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Sarah wrote a detailed article which we have turned into three blog posts to be shared with you. This is the second blog in the series.

You can read her first blog post here.

In many rural and peri-urban areas, urban expansion and agricultural intensification are eroding the natural habitats on which wild bees depend.

Let’s look at the agricultural model. Not only is the use of pesticides poisoning wild bees, but the spread of crops such as wheat and vines, which do not produce nectar or pollen, is also depleting food resources in rural areas. In addition, modern farming techniques such as ploughing and early mowing destroy the nests of bees that nest in the soil. Last but not least, the monoculture farming model creates ‘biological deserts’ where the diversity of floral species is greatly reduced, while at the same time reducing the availability of food for many species that pollinate only a single species. In other words, the loss of pollinators is a catalyst for the loss of agricultural crops.

In this way, current agriculture may be contributing to its own decline, as wild bees play an essential role not only in keeping agricultural systems productive, but also in ensuring their resilience. (See the section “The role of wild bee as a pollinating insect” in Part 1 of this blog series.)

One of the agriculture industry’s responses to this decline is the use of industrial beekeeping, that is, colonies of honey bees. Honey is sold in a dynamic international market, which today is influenced by greenwashing practices. In short: the honey bee is perceived not only as a producer of economic goods (honey, propolis, etc.), but also as a symbol of a healthy, thriving ecosystem. This makes honey bees attractive to a wide range of companies and lobbies that adopt this ‘green’ image and support beekeeping, thereby strengthening their environmental reputation and encouraging exponential growth in the bee population. This massive influx of domestic bees means that the number of bees in a given area suddenly multiplies, increasing the risk of competition for nutrients.

In fact, the installation of an apiary implies a parallel increase in the demand for resources (pollen, nectar). These thousands of bees, when concentrated in one place, can have a considerable energy requirement, leaving fewer resources for wild bees and contributing to their gradual disappearance from the ecosystem.

A European honey bee (Apis mellifera).

All these actions and anthropological changes are contributing to the disappearance of wild bees and affecting the entire ecosystem. For example, if the honey bee dominates access to food resources, whole populations of other pollinating insects can be affected, and with them the animal and plant species that depend on them for food or reproduction. This is known as a ‘trophic cascade’, a somewhat fancy term used to describe the chain of effects that the disappearance of one element has on the ecosystem.

But how can the disappearance of a particular plant or insect have such an impact on the rest of the ecosystem? The answer lies in one word: interconnectedness. Put simply, a functioning ecosystem includes diverse yet interconnected elements. In this context, plants and pollinators interact in a symbiotic relationship in order to grow and reproduce.

Take the example of wild bees: if certain species disappear, the plants that depend on these pollinators can’t reproduce fully and gradually disappear from the landscape, leading to a decline in plant diversity. The domino effect continues when a plant species that is the primary food for another species disappears.

To better understand the trophic cascade, let’s take a look at the famous bumblebee. A study shows that Bombus terrestris is particularly well adapted to pollinating aconite (Aconitum spp.) (Marshall et al. 2020). Thus, the disappearance of bumblebees would lead to a reduction in the reproductive rate of aconite, reducing the number of seeds in the ecosystem. Fewer seeds would mean less food available for rodents (voles, field mice, etc.) that are directly dependent on this plant for food. The trophic cascade continues, eventually reaching the predators that feed on these rodents, etc.

A hairy-footed flower bee (Anthophora plumipes).

The gradual disappearance of wild bees also affects our own food production, both in terms of quantity and quality.

Remember that domestic bees, generally portrayed as the most important pollinators, represent only one species out of around 2,000 bee species in Europe. As such, wild bees play an essential complementary role in the pollination of many crops and fruit trees (Kleijn et al. 2015), and their disappearance means a decrease in the pollination rate. This in turn affects crop yields; less pollination means less reproduction, which means fewer vegetables and fruits to harvest, which seems logical.

But… how can the disappearance of wild bees affect the quality of crops?

Let’s take apples as an example. In 2022, a study conducted by several scientists highlighted the importance of wild bees for apple quality, by analysing the ecological mechanisms at work during pollination. Thanks to their morphological and behavioural diversity, wild bees visit flowers from different angles and at different frequencies, which improves the deposition of pollen from one flower to another. On the contrary, in the absence of this diversity, pollination becomes less balanced and efficient, resulting in poorer quality fruit, such as smaller or deformed apples (Weckers et al. 2022).

Finally, wild bees contribute to the resilience of the ecosystem around them, especially agricultural crops. How do they do this? Again, honeybees are just one species among thousands, pollinating flowers in a way that is specific to their species, behaviour and morphology. On the scale of an ecosystem, with dozens or even hundreds of other bee species, pollination becomes more complete. Experts call this ‘genetic cross-fertilisation’ (Vaissière, 2005), meaning the exchange of genes within a plant population by bees and other pollinating insects that carry pollen from one plant to another. As a result, the production of genetically diverse seeds increases local genetic diversity, making plants and agricultural crops more resilient to disease, pests and climate change (Garnett et al. 2013; Wentling et al. 2021).

To sum up, wild bees are not just ‘’back-up‘’ pollinators that play only a secondary role in an ecosystem or in certain agricultural crops and fruit trees. In many cases, the diversity of their approach to pollination enhances crop quality and resistance.

To better understand the role of wild bees in the Algarve, let’s take a look at the region’s agricultural economy: many local crops, whether perennial or annual, depend on pollinating insects for their reproduction, including wild bees.

Almonds are a good example. The almond tree (Prunus dulcis) relies on wild pollinators such as Osmia (Osmia spp), a species of wild bee that is particularly effective at pollinating its flowers – along with honeybees (Saez et al. 2020; Bosch et al. 2021). Thus, a decline in wild bee populations, particularly in the context of food competition with honeybees, could have a direct impact on almond yields (Alomar et al. 2018).

That’s not all: bees also visit gardens in the Algarve, whether they are small private gardens or larger gardens for commercial purposes (e.g. market gardens). They are particularly keen on crops such as courgettes and cucumbers – or tomatoes, where the bumblebee is particularly valued for its pollination work in greenhouses (Nayak et al, 2020). Strawberries also benefit from more efficient pollination by wild bees, resulting in heavier fruit, according to a study by MacInnis and Forrest (2018).

In short, wild bees are still contributing to agricultural yields despite the ongoing destruction of their habitats – some of it by the same industrial farming systems. An alarming fact that is still far too little known to the general public. And yet wild bees are still out foraging. They come out at dawn every morning and will continue to visit flowers every day, covering their nests with petals or digging in dead wood. Fulfilling their invaluable role in pollinating the surrounding ecosystem.

For that reason alone, it’s worth trying to protect our local bee population. While changing the current monocultural agricultural model on an international scale may seem a little ambitious, there are many small actions that can make a big difference to the wild bees around you.

Wild bees are under the increasing threat from modern industrial agriculture and sprawling urbanization as well as competition from industrial beekeeping.

The loss of these key pollinators results in the disruption of healthy ecosystems by trophic cascade. It also impacts food production resulting is less food with lower quality.

To learn more about Sarah and her work, check out her LinkedIn profile.