Background: why conserve pollinators?

What is pollination?
Pollination occurs when pollen is moved within flowers or carried from flower to flower by pollinating animals or by the wind. The transfer of pollen between flowers of the same species leads to fertilization, and successful seed and fruit production for plants.  Pollination ensures that the plant will produce full-bodied fruit and viable seeds. For crop producers, this means good yields of high quality produce, for consumers, it means the availability of a range of fruit and vegetables at an affordable price, and for the wider environment, it means a healthy ecosystem.

 

Who are the pollinators in Ireland?
Although a range of animals visit flowers to collect food (nectar and/or pollen) the most important pollinators in Ireland are insects; particularly bees and hoverflies.

 

Globally, bees are the most important pollinator because they visit flowers to collect food for their larvae, as well as feeding exclusively on flowers as adults. Hence the entire life-cycle of bees is dependent on interactions with flowering plants. Of the 100 crops that provide 90% of the world’s food supply, 71 are pollinated by bees. 

 

While adult hoverflies feed mainly on nectar and pollen, the larvae of many species are voracious predators of aphids and other pests. As a result, hoverflies are important as they contribute to both pollination and pest control.

 

In Ireland, there are 97 different species of bee, including the familiar honeybee (1 species) and bumblebee (20 species). The remaining species are solitary, meaning they do not form colonies. Only the honeybee produces commercially extractable honey. There are 180 species of hoverfly in Ireland.

The honeybee has long been domesticated by humans and managed for honey production and/or crop pollination. In the last 20 years, bumblebees have been available commercially for use in covered (glasshouse) crops. Recent collapses in honeybees due to a range of factors have caused widespread concern with regards to crop pollination, particularly in North America. Global honeybee declines have highlighted the risks associated with the reliance on a single pollinating species. Furthermore, recent studies in the UK have shown that the honeybee is not as important as a crop pollinator as previously believed, and it makes up only a small fraction of insect visits to flowers in Irish agricultural systems.

 

The importance of wild, non-managed bees as pollinators of not only crops, but also wild plants is becoming more and more apparent.  Studies have shown that a diversity of pollinator types is important for maximizing pollination.


“To provide stable pollination services for our crops, crop wild relatives (potential future crops) and other wild plants, we need to maintain both wild and managed pollinators in the landscape.”

 

Why does pollination matter to us?

Reduction in the diversity/abundance of pollinators and/or pollinator loss can reduce crop yield. The annual value of pollinators for human food crops has been estimated at €153 billion world-wide, £603 million in the UK and €53 million in Ireland. Regional estimates of the value of pollinators to individual crops have also been made, with values of up to $41million for blueberry pollination in Oregon (USA), £36.7 million for apples in the UK and €3.9 million for oilseed rape in Ireland. The cost of replacing pollination services provided by animals by artificial means (e.g. human hand pollination or pollen dusting) can be substantially higher. Furthermore, animal-pollination can improve shelf-life of soft fruits, further increasing their value. Wild pollinators can act as insurance against decline in managed pollinators, driven by pest/disease outbreaks. Pollination also improves the nutritional value of some crops and animal-pollinated crops are crucial for providing vitamins, anti-oxidants and other essential nutrients to the human diet. Pollination also has a non-market value as pollinators contribute directly and indirectly to human well-being in other ways. For example, people derive pleasure from bees and pollinator-dependent habitats such as flower-rich meadows. The value of this is harder to determine, but is demonstrated by public support for organisations such as the Bumblebee Conservation Trust and Limerick’s Buzzing.

Are pollinators in trouble in Ireland?

Unfortunately, Irish pollinators are in decline, with 30% of the wild bees in Ireland
considered threatened with extinction according to IUCN criteria.
The main drivers of pollinator decline include:

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1. Habitat loss, fragmentation and degradationHomelessness

Loss of natural and semi-natural habitats has been a key driver in pollinator declines. The availability of food plants and nesting sites has been drastically reduced through conversion of low-intensity farmland and semi-natural land to intensive farmland, forestry and urban/ industrial use. Declines have occurred across all habitats from grasslands to woodlands, sand dunes, peat lands, and mature hedgerows. Those areas of habitat that remain have also declined in quality. This change has had most impact on wild pollinators because they are totally reliant on resources available in the landscape. It has been shown that the number of visits to crop fields by wild pollinators tends to drop with distance from semi-natural areas. Effective pollination by wild pollinators requires crop land to be interspersed with more natural areas requiring a landscape scale/farm-wide approach.




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2. General declines in wildflowers within the landscapeHunger

It is important that pollinators have a balanced diet from a range of plant species. They require food (nectar and pollen) throughout their active foraging season which lasts from early spring until late autumn. Declines in wildflowers are largely due to changing farming practice, particularly the movement from hay to silage production. Increases in the amount of fertiliser applied to arable fields has resulted in increased crop yields, but has led to a strong decline in species diversity and flower richness within managed fields and in semi-natural habitats adjacent to fertilised fields. Our tendency to tidy up the landscape rather than allowing wildflowers to grow along roadsides, field margins, and in parks and gardens is also playing a role in fewer of these resources being available. Maintaining pollination service requires providing a sufficient abundance and diversity of food plants across the landscape for our pollinators from early spring to late autumn. We are asking our pollinators to perform services in an increasingly inhospitable landscape.

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3. Pests and diseaseSickness

When managed pollinators are imported into Ireland they can inadvertently bring with them new pests and diseases. Pests and diseases are the main threat to honeybees, particularly an introduced parasitic mite (Varroa destructor), other invertebrates, bacteria, fungi and viruses. Wild bees may be affected by disease transfer from imported bumblebees that have been released in glasshouses and polytunnels, and by pests and diseases traditionally considered confined to honeybees. Emerging pests and diseases are considered one of the key risks to wild pollinators, particularly bee populations. Vigilance and swift action from those working with managed pollinators and assessing potential future threats is essential.




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4. PesticidesPoisoning

To meet global population growth and resultant food demand, the pressure on pesticides (insecticides, herbicides, fungicides) to deliver higher standards for crop protection has increased; with agriculture currently using the highest volume of pesticides than at any other point in history. These insecticides, herbicides and fungicides are applied to crops, but reach the pollinators through pollen, nectar, and through the air, water or soil. Although herbicides and fungicides may not have direct toxic effects on pollinators, herbicides reduce the amount of food available, and fungicides may interact with other pesticides and have negative impacts on bees. Insecticides can get into the nectar and pollen either as a result of foliar spraying or via systemic treatments whereby the pesticide is taken up by the plant and expressed in all plant tissues. Although the relative role of pesticides in global pollinator declines remains poorly understood, it is now more evident than ever that some insecticides show clear negative effects on the health of pollinators, both individually and at the colony level. Whilst all pesticides pose a risk to pollinators if inappropriately applied, recent concerns have focused on the risks associated with the widespread use of a class of systemic insecticides, the neonicotinoids. Although the type and intensity of pesticide use varies across Ireland, there has been no field-level research on their impacts on pollinators in Ireland. The only Irish research related to pesticides and pollinators looked at organic dairy farms and found that they had higher numbers of both flowers and insects. Continued research into Irish agricultural systems, chemical controls and the effect on pollinators is essential to future management of our pollinator resource.

5. Climate changeChanging environment

Recent studies have shown that wild pollinators are highly vulnerable to climate change. The impact of climate change on pollination service can be difficult to predict. However, with likely changes in the timing of flowering, the occurrence of important life cycle events of pollinators (e.g. emergence from hibernation, production of offspring etc.), and the geographic ranges of plants and pollinator species, there is the potential for mismatches between plants and their pollinators, as well as risks associated with more frequent severe weather events (e.g. storms, floods, late frosts etc.). This means that crops or wild plants may flower before their pollinators emerge from hibernation; or the pollinators themselves may emerge first and find it difficult to survive due to a lack of food sources if the crops or wild plants are not yet flowering. For habitat restoration work in which wild flowers are deliberately planted within the landscape, it is preferable to use locally collected seed as it is more likely to be in sync with the local climatic conditions. It is important to increase the connectivity and quality of pollinator friendly habitats so that pollinators can move in response to climate change and we retain as much resilience within our ecosystems as possible.