Disappearing Pollinators By Ed Powers

August 29, 2019

Picture Courtesy University of Leeds

These hard-working animals help pollinate over 75% of our flowering plants, and nearly 75% of our crops. Often we may not notice the hummingbirds, bats, bees, beetles, butterflies, and flies that carry pollen from one plant to another as they collect nectar. Yet without them, wildlife would have fewer nutritious berries and seeds, and we would miss many fruits, vegetables, and nuts, like blueberries, squash, and almonds . . not to mention chocolate and coffee…all of which depend on pollinators. But they are disappearing and at an alarming rate. While all pollinators are important, we will be focusing on honeybees (though many of the causes relate to all pollinators not just honey bees).

Picture Courtesy National Audubon Society

There are a number of pressures on pollinator populations, but there is lack of information about their relative importance or to what extent they have led to the declines we are now seeing. Possible causes include

The loss of basic habitat requirements in our landscapes such as floral resources other than flowering crops that provide food to pollinators. Flowering crops are usually in bloom for only a fraction of a pollinator's life cycle, so in order to survive and reproduce effectively they need alternative sources of nectar and pollen throughout their active season. The loss of other basic needs such as nesting sites and materials may also contribute to the problem.
The simplification of the landscape with the promotion of monoculture crops, larger fields and less traditional features such as hedgerows, set-aside land and wildflower rich grassland. This results in less of the food and nesting resources occurring in landscapes and the isolation of resource-rich semi-natural habitats.
The intensive use of agro-chemicals including pesticides that may have a direct effect on insect pollinators, and herbicides that remove important floral resources. Pesticides are substances used to eliminate unwanted pests. Insecticides are a subset of pesticides focusing on insects. Unfortunately, honey bees are insects and are greatly affected by insecticides. There are several ways honey bees can be killed by insecticides. One is direct contact of the insecticide on the bee while it is foraging in the field. The bee may then die and does not return to the hive. In this case the queen, brood and nurse bees are not contaminated and the colony survives. The second, more deadly, way is when the bee comes in contact with an insecticide and transports it back to the colony, either as contaminated pollen or nectar or on its body.
Pests and diseases affecting domesticated pollinators such as honey bees and which may spread to wild populations.
Over-reliance on domesticated honey bees for pollination which may compete with wild pollinators for scarce resources.
Colony Collapse Disorder is the phenomenon that occurs when the majority of worker bees in a colony disappear and leave behind a queen, plenty of food and a few nurse bees to care for the remaining immature bees and the queen. Although once thought to be of a major impac,t it is now less impactful.

Research into these pressures has typically focused on a single cause, but in reality they may interact with each other. For example, a lack of floral resources occurring in the countryside due to intensive farming may lead to nutritional stress in insect pollinators which in turn can make them more vulnerable to attack from pests and diseases or to the effects of pesticides. There is therefore a need for research to identify the underlying causes of pollinator declines and the interactions between them, and this is one of the broad aims of the work funded by the UK Insect Pollinator Initiative.