Cocoa, melons or even carrots. Worldwide, 75% of the species used for crops depend – totally or in part – on bees and other pollinators for their reproduction. The figure rises to 87% for wildflowers. What would we be left with if pollinators disappeared?
To understand their essential role, one must understand pollination itself. This can happen in different ways: thanks to the wind, gravity, or even pollinators. In the latter case, an animal moves pollen grains from the anthers (male part of the flower) to the stigmas (female part) of another compatible flower. The result is seeds and sometimes fruits or vegetables, which are then consumed by humans.
Mutual influence between plants and pollinators
This process is the result of a co-evolution – a mutual influence – between plants and pollinators, built over thousands of years. “Plants have developed specific strategies such as the production of nectar to attract animals allowing them to reproduce.illustrates Benoît Geslin, lecturer in ecology at the Mediterranean Institute of Biodiversity and Marine and Continental Ecology. These animals therefore do not perform pollination consciously. »
On the scale of an orchard or a field, this pollinating machine is extremely effective. “In honey bees, it is estimated that a single forager must visit a hundred flowers to fill its crop. (his stomach) and then transport it to the colonysays Mathieu Lihoreau (1), research director at the CNRS and specialist in bee intelligence. She repeats this ten times a day, sometimes for several weeks..
Declining bees and butterflies
If the honey bee is regularly in the spotlight, there are actually 20,000 species of bees around the world, including 850 in France. These species are primarily responsible for pollinating crops and wildflowers in the territory. But some plants depend on other pollinators: insects, birds, bats, mammals. The cocoa tree, for example, is mainly pollinated by flies, and some flowers can only be pollinated by a particular species.
However, a large number of these species are in decline worldwide: 16.5% of vertebrate pollinators are threatened with extinction. In Europe, bee populations are declining by 37% and butterfly populations by 31%. Among bees, the main culprits are the use of pesticides – including neonicotinoids, now largely banned in France – and the destruction of natural areas, which affect wild bees. Other factors, such as the appearance of certain parasites, are also involved.
Without pollinators, 12% of cultivated species are threatened
However, the disappearance of pollinators would not lead to the disappearance of all human cultures. Some, like wheat, corn or rice, do not depend on it at all. Others are only partially linked to it, but would still be affected: pollination influences the number of seeds produced, which then affects the size of the fruits.
In an orchard without pollinators, there would only be a few tiny apples, 85% of which depend on insects. Scientists who have worked on this hypothesis have estimated that in the absence of pollination, we would lose 35% of world production in tonnage, all crops combined.
About 12% of cultivated species, including melon, coffee or raspberries, would thus see their production drop by more than 90%, i.e. a virtual disappearance. However, crops that depend on animal pollination are also among the richest in crucial nutrients for human health: vitamin A, folic acids, iron, etc.
Not to mention that these figures only take into account the direct dependence of plants on pollinators for yields. Pollination is also essential for the production of seeds – and therefore seeds – for certain plants, such as carrots.
Food security at stake
In some countries, especially in the South, the fruits of pollination are vital for the survival of certain populations. “In Argentina, apples are the first orchard fruits exportedrecalls Benoît Geslin. Pollination is therefore strategic in terms of food security, but also crucial for the economy, because it allows foreign currencies to enter. »
If the negative effects of the decline of pollinators on agricultural products are being demonstrated, those on natural environments are more difficult to measure. “Scientists suspect a strong link between the decline of certain plants and that of pollinators”, explains André Pornon, researcher on pollination networks, at the Evolution and Biological Diversity laboratory at the University of Toulouse 3 Paul-Sabatier. “On the other hand, the complexity of ecosystems makes it difficult to establish a causal link. »
About 308,000 species of the world’s flowering wild plants depend, at least in part, on animal pollination for their reproduction. Wild plants which themselves provide food and shelter for other invertebrates, mammals, birds and others.
The limits of adaptation
Good news: some plants have already evolved to adapt to the decline of insects. A study conducted over twenty years and published in 2015 showed that the cornflower had evolved to become more attractive in areas where pollinators had become rarer, the size of the flowers having increased to attract them.
But the adaptation of living organisms (plants and pollinators) has its limits: climate change creates new stresses for them. According to IPBES (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services), the equivalent of the IPCC for biodiversity, the rate of climate change is expected to exceed the maximum rate at which many pollinator groups are able to disperse or to migrate.
The bird, like this Grey-bellied Ariadne from Costa Rica, is a pollinator. / Michael & Patricia Fogden/Minden Pictures/Biosphoto
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Pollinators in France
In France, approximately 70% of the 6,000 plant species listed – wild and cultivated – are pollinated by insects.
Bees – wild and domestic – are the first pollinators. But pollination is also carried out to a lesser extent by other hymenoptera (such as ants), butterflies, beetles and certain diptera (flies, mosquitoes, gnats, etc.).
The share of agricultural production attributable to the action of pollinators is estimated between 2.3 and 5.3 billion euros per year.