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The Atlas of the Wild Bees of Brussels, funded by Brussels Environment and implemented by the team of Prof. Nicolas Vereecken at the Agroecology Lab of the Université Libre de Bruxelles, aims to better define the diversity, distribution, abundance and needs of more than 150 species of wild bees encountered in Brussels and to produce a document freely accessible and summarising the state of current knowledge.

WildBnB is the acronym of 'Wild Bees and Brussels' and refers to the concept of Bed and Breakfast (BnB), as our wild bees need nesting sites (bed) and host plants (breakfast) to survive and thrive in our urban environments. 

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Stéphane De Greef
Project coordinator

Agroecology Lab

ULB, Campus de La Plaine

T: +32 (0)2.650.6081

E: stephane.de.greef at ulb.ac.be

© 2019 WildBnB - ULB Agroécologie

All images by Nicolas Vereecken except when mentioned

Main threats

Are all bee species threatened?

We often hear and read that all bee populations are collapsing around the world, but what is it really? The first question to ask before answering is 'what bees are we talking about?', as the situation varies greatly from one species to the other. Some bees are doing well while others are threatened or on the verge of extinction. There are three main categories:

The European honey bee (Apis mellifera) is at no risk of extinction (© Nicolas Vereecken)

1. The European honey bee (Apis mellifera), which is domesticated and probably no longer exists in the wild in Europe, is a farmed animal whose populations are easily managed and multiplied by beekeepers. Although negatively impacted by diseases, parasites and some pesticides, the number of colonies is stable or increasing in Belgium. They are therefore not threatened with extinction and do not need to be 'saved', despite what many websites say!

The European orchard bee (Osmia cornuta) is still doing fine in cities (© Nicolas Vereecken)

2. Some species of wild bees such as the buff-tailed bumblebee (Bombus terrestris) and European orchard bee (Osmia cornuta) have flexible ecological needs and have therefore adapted well to the changing land use in Belgium over the last centuries. Foraging on a wide range of wild plants and crops (including many of our fruits and vegetables), nesting in parks, gardens and wastelands, they are doing well in our region and continue to ensure their role as pollinators in natural, agricultural and urban areas.

Melitta nigricans only collects pollen from purple loosestrife (Lythrum salicaria)(© Nicolas Vereecken)

3. Other species of wild bees, such as the purple loosestrife melitta (Melitta nigricans), have very restricted ecological niches, foraging only one or a few plant species (monolectic and oligolectic bees), or needing particular places or uncommon materials for nest construction (for example very warm sandy soils, empty snail shells or plant fibers). Several dozen of these species are unfortunately in decline or have already disappeared from the Brussels region or even from Belgium, over the last decades.

What are the main threats to wild bees?

On the basis of European Red List of Bees and other relevant studies, current threats can be grouped into five broad categories:

1. Agricultural expansion and intensification

Over the last centuries, many natural areas (forests, grasslands, wetlands, etc.) have been progressively converted to agricultural and livestock production areas, resulting in large scale habitat loss and habitat degradation, notably through the application of insecticides and herbicides, intensive large-scale monoculture and the replacement of hayfields with intensive livestock feed.
 

Specifically, each species of wild bee needs suitable nesting sites (bare, well-drained, warm soil, sandy soil, gentle slope or vertical earth wall, hollow stems, piles of rocks, snail shells, etc.), as well as one or more species of host plants to collect nectar and pollen from. The conversion of natural areas to agriculture has greatly reduced the area available for these nesting sites and the abundance, density and range of these plants essential to the life cycle of many species of bees.

A meadow with a wide diversity of host plants (© Nicolas Vereecken)

A crop production area with low diversity of host plants (© Nicolas Vereecken)

2. Pollution and pesticides

Often referred to as the only or main cause of the 'bee-pocalypse', pesticides (mainly herbicides, insecticides and fungicides) are just one of many factors behind the decline of bees. Unfortunately, most toxicological studies have been carried out on the European honey bee (Apis mellifera) and the buff-tailed bumblebee (Bombus terrestris) and we're still lacking consistent data to fully understand the impact of these substances on other species of wild bees.

Some insecticides used in agriculture and horticulture have a significant effect on non-target species, leading to increased mortality and, at sub-lethal doses, affecting the behaviour of some species and making them more susceptible to diseases and pests. Herbicides also threaten wild bees by destroying 'weeds', native plants providing pollen and nectar essential for bee survival. Fungicides would also have an impact on the health and survival of some bumblebee species.

Insecticides and herbicides are commonly used in gardens (© Stéphane De Greef)

Pesticides can kill, disorientate or weaken some bee species (© Stéphane De Greef)

3. Industrial and urban development

In addition to the loss of habitat and floral resources related to agriculture, many natural or semi-natural sites have been destroyed in recent decades to make way for industrial and urban areas, especially in the Brussels region. As a result of this change of land use, unable to find their host plants and without access to healthy soils or hollow stems for nesting, most wild bees can disappear from the landscape over a matter of months or years.

Urban wastelands, these 'abandoned areas' in the heart of our city, are safe havens for dozens of wild bee species, where they have access to a wide range of nesting sites, great floral diversity and low pesticide contamination. Every year, unfortunately, many urban wastelands are developed to make room for new housings, shopping centers or car parks, resulting in the instant disappearance of many species of wild bees and countless other plants and animals.

The friche Josaphat in Schaerbeek hosts more than 70 species of bees (© Jens D'Haeseleer)

A former wasteland in Tour et Taxis converted to a flowerless car park (© Stéphane De Greef)

4. Climate change

Even though climate change is not perceived in our daily lives, the increase of average temperatures, the periods of extreme drought, floods or dog days can cause catastrophic damage to bee populations and their host plants. Some spring species emerging too early because of a mild winter may be decimated by late frost, and others may emerge before or after the flowering season of their host plant, leaving them without food. These phenomena remain poorly understood and it is essential to carry out more studies on this critical topic.

A demonstration in 2019 in Brussels to ask the government to implement concrete actions against climate change (© Stéphane De Greef)

5. Invasive species, diseases and parasites

The arrival of invasive species can cause serious disturbances in natural, agricultural and urban environments. Invasive plants such as Japanese knotweed (Fallopia japonica) can quickly cover large areas of land and cause the disappearance of native flora and sun-exposed nesting sites.

Several studies have also shown that honeybees negatively impact wild bee populations, chasing them away and reducing their density in a significant way, notably by competing with wild bee for floral resources, by outnumbering wild bees because of their efficient recruitment behaviour, but also by massively exposing wild bees to parasites and viruses .

Japanese knotwee (Fallopia japonica) crowding an area that used to harbour a wide diversity of native plants providing nectar and pollen to wild bees (© Stéphane De Greef)