The role of pollinators in agriculture

Ecosystem services are benefits for the human population that derive directly or indirectly from ecosystem functions, being considered essential for the maintenance of life on our planet, affecting, to some extent, the global economy. Within ecosystem services, pollination is considered one of the most important for life, being a process that benefits flowering plants, animals and humans.

The ecosystem service of pollination can be divided into different categories, depending on the benefits it provides. The regulatory service is related to the maintenance of genetic variability of native plant populations. Pollination also guarantees the provision of resources for human nutrition, that is, a diversified supply of grains, fruits, vegetable oils, honey, among others. Furthermore, the ecosystem service of pollination ensures the promotion of cultural values ​​related to traditional knowledge.

Pollination and pollinators

Pollination is the process of transferring pollen from the anthers to the stigma of a flower of the same species (Figure 1). The transfer of pollen from the anthers to the stigma of the same flower is called self-pollination. The transfer of pollen from one flower to the stigma of another plant's flower is called cross-pollination. The pollination process can be carried out by biotic (insects and vertebrate animals) and abiotic (wind and water) vectors. When mediated by biological vectors, pollination is considered an ecological interaction between flowering plants and pollinating agents (pollinators). However, not all animals that visit flowers are pollinators. A floral visitor can be any animal that visits a flower, while a pollinator is one that transfers pollen from the anthers to the stigma.

Pollinating organisms can be vertebrate animals – such as bats, hummingbirds, small lizards – and invertebrates – such as bees, lepidopterans (butterflies and moths), flies, wasps and beetles (Figure 2). Bees are the main group of pollinators and, in Brazil, for example, they contribute to the pollination of 78% of plants used for food, in addition to being the pollinators of the majority of native plants in different plant communities. As a result of pollination, fertilization occurs and the subsequent formation of fruits and seeds, which will be used in the dispersal and propagation of the plant species, as well as in feeding animals and humans.

Pollination in food production

Most flowering plants depend, to some extent, on pollinators for seed and fruit formation to occur. It is estimated that around 2/3 of cultivated plant species used in food depend on or benefit from the presence of pollinators. The dependence on pollination of a given species is a measure of the increase in production obtained through the action of pollinating animals.

For those where pollination is considered “essential”, productivity increases due to the action of pollinators vary from 90% to 100%. For at least 35 species of plants used in human food, pollination is essential, as in the case of apple cultivation (Malus domestica), watermelon (Citrullus lanatus), melon (Cucumis melo), tangerine (Citrus reticulata) and passion fruit (Passiflora).

For plants whose dependence on pollinators is “high”, the productivity increases resulting from the action of pollinators vary between 40% and 90%. This group includes important cultivated species, such as sunflower (Helianthus annuus), peach (Prunus), plum (P. salicina), onion (Allium cepa) and canola (Brassica).

In some cultures, such as coffee (Coffea arabica), soy (Glycinemax), orange (C. sinensis) and pepper (Capsicum annuum), dependence on pollinators is “modest”, productivity increases resulting from the action of pollinators vary between 10% and 40%. There is still a last group in which dependence on pollination is “little”, productivity increases vary from 0 to 10%. This last group includes bean crops (Phaseolus), grape (Vitis labrusca) and tomato (Solanum lycopersicum).

The presence of pollinators can increase fruit production and quality even in plant species that exhibit self-fertilization, such as coffee, canola, soybeans and cotton. For example, the flowers of coffee culture (Coffea arabica L.), one of the main agricultural commodities in Brazil, are self-compatible, that is, both self-pollination and cross-pollination result in fruits. Despite this, a study demonstrated that the presence of cross-pollination, carried out by pollinators, increased harvest yields on coffee farms by up to 30%. Canola (Brassica L.), an important agricultural crop in the southern region of Brazil, presents self-compatibility. Despite this, pollination of canola flowers by Apis mellifera resulted in a 45,9% increase in seed production.

In soybean and cotton crops, where dependence on pollinators for reproduction is modest, there is increasing evidence that the presence of pollinators, especially native bees, facilitates cross-pollination and results in increased fertilization and productivity. For example, in a study carried out with cotton grown in two different Brazilian biomes (Amazon and Caatinga), it was observed that pollination carried out by bees increased the average weight of bolls, with an increase of 12% in fiber weight and 17% in fiber weight. number of seeds. In soybean cultivation, there is evidence demonstrating that floral visitation by bees does not apis reduces flower abortion and induces increases in grain yield. For example, a study showed that the presence of pollinators in soybean growing areas increased productivity by 6,4%, and the insertion of soybean colonies A. mellifera resulted in an 18% increase in crop productivity. These results are particularly important in the context of a global decline in pollinator populations, and highlight the need for further studies to understand the diversity of pollinators associated with agricultural crops.

Pollination service

The value of pollination in maintaining life is incalculable. However, it is estimated that the increase in agricultural productivity and the quality of plant products due to pollination is equivalent to R$43 billion annually in Brazil. Worldwide, estimates indicate that the global economic value of the ecosystem service of pollination is between US$235 billion and US$577 billion per year.

According to a study that evaluated the dependence on pollinators for 141 crops used in food in Brazil, 85 species are dependent on the pollination service. This same study demonstrated that crops that depend on some degree of animal pollination generate income of around US$45 billion per year, with the contribution of pollinators corresponding to 30% of the production of total agricultural income from these crops (approximately US$12 billion/year).

Soy, coffee and orange crops are classified in the group of plants with modest dependence on pollinators. Despite this, the agricultural income obtained from pollinators in soybean cultivation corresponds to R$ 25 billion annually, while for coffee the contribution of pollinators is R$ 5,2 billion annually and in orange cultivation the income obtained from of the ecosystem service of pollination is approximately R$2,2 billion annually (Figure 3).

Outlook for pollinators

Through pollination, pollinators play a fundamental role in the reproduction of flowering plants, contributing to the conservation of biodiversity in natural ecosystems and food production. However, a decline in populations of wild or managed pollinators (e.g.: Apis mellifera) has been reported in several parts of the world, exposing these animals to the risk of extinction. The loss of natural habitat, the irrational use of pesticides, diseases, among others, are among the main causes of the decline of pollinators.

Pollinator-friendly practices are ways to reduce threats, improve the ecosystem service of pollination and add value to agricultural production. Pollinators need food (nectar, pollen, oil) available all year round, nesting and breeding sites. Therefore, maintaining natural habitats, recovering degraded vegetation areas, ensuring the flowering of native plants, creating ecological corridors, are practices that improve yields and the quality of crops. And the more diverse the community of these animals is in agricultural environments, the better the results will be.