Bees and pollinators

Who the pollinators are

Most flowering plants cannot move, so they pay animals to move their pollen. The fee is nectar and surplus pollen; the service is fruit and seed. According to the assessment of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES, 2016), more than three quarters of the leading types of food crops worldwide depend at least in part on animal pollination.

When people think of pollinators, they think of the honey bee. It is one species among many. The first European Red List of Bees, presented by the IUCN in 2015, assessed 1,965 wild bee species in Europe alone. Most of them are solitary: each female digs or finds her own nest, fills it with pollen and nectar and lays her eggs there. Bumblebees live in small colonies that last one season. Beside the bees work hoverflies, beetles, butterflies, moths and wasps, each with its own flowers and its own hours of the day.

The same Red List found 9.2 percent of the assessed species threatened with extinction, and for more than half there were not enough data to judge. It named the loss of flower-rich grassland, pesticides and fertilisers, urban growth, fire and climate change among the causes.

How they work in the system

Pollination is the clearest case of what David Holmgren calls a renewable service: a benefit received from living things without consuming them, which lasts only as long as the relationships behind it stay intact.

That wild insects carry much of this service was shown by Lucas Garibaldi and colleagues in 2013. Across 41 crop systems on every continent, flower visits by wild insects raised fruit set in all of them, while visits by honey bees did so significantly in only 14 percent. More wild visits improved fruit set about twice as much as the same increase in honey bee visits, and the two worked side by side: hives added to wild pollination but did not replace it.

The honey bee still has its place. A colony gives honey, wax and propolis and pollinates many crops reliably. But a large number of hives draws heavily on the same flowers. A systematic review by Rachel Mallinger and colleagues in 2017 found negative effects of managed bees on wild bees in about half the studies on competition, and possible harm through disease in most studies on that question, though few measured lasting effects on populations. In a permaculture design, honey bees are welcome guests when the land offers enough flowers for everyone.

How to begin

1. Flowers in every season. A garden full of blossom in April and bare in July starves its insects in summer. Plan a flowering sequence that covers every month in which insects fly, with trees, shrubs, herbs and ground covers. In dry climates, the gap usually falls in late summer, and drought-tolerant shrubs and herbs of the local flora close it best.
2. Many kinds of flowers. Open, shallow flowers feed short-tongued bees and flies; deep tubes serve bumblebees and moths. Native plants support the most specialised species. Plants on the EU list of invasive alien species, such as common milkweed, sometimes recommended for pollinators elsewhere, are not planted.
3. Places to nest. Leave a few sunny, bare, well-drained patches of soil uncovered, even in a mulched garden. Let hollow and pithy stems stand over winter, keep some dead wood and old walls.
4. No poisons. Insecticides kill pollinators directly; herbicides remove their flowers. A system that keeps pests in balance through diversity needs neither.
5. Water. A shallow dish with stones or a pond edge with a gentle slope gives insects a place to drink without drowning.
6. Hives with knowledge. Keeping honey bees is a craft. A local beekeepers' association can advise on the local rules, the right site and the number of hives the land can carry.

An example from the world

In the Central Valley of California, one of the most intensively farmed landscapes on earth, Lora Morandin and Claire Kremen compared field edges replanted with native flowering shrubs and perennials with ordinary weedy edges. The restored hedgerows held more native bees and hoverflies and more kinds of them; about 40 percent of the bee species found on hedgerow flowers were found only at the hedgerow sites. The hedgerows did not pull pollinators away from the crops. They exported native bees into the neighbouring fields (Ecological Applications, 2013). A strip of flowering edge, in other words, works for the whole farm.

Common mistakes

• Counting on honey bees alone. They add to wild pollination, they do not replace it.
• A bee hotel instead of a habitat. Only cavity nesters use it, and without flowers nearby it helps no one. Most wild bees need bare ground.
• Every square metre mulched. Soil cover is a strength of permaculture, but ground nesters need a few open, sunny spots.
• Tidying everything in autumn. Dead stems and seed heads shelter the next generation of bees and other insects.
• A spring-only garden. Without flowers in summer and autumn, the insects that arrived in spring go hungry or leave.

Further in the TerraWiki

• Use and value renewable resources and services: pollination as a service that lives on relationships.
• Use and value diversity and the plant guild: flowers chosen for the insects they feed.
• Use edges and value the marginal: hedgerows and borders as the richest places for pollinators.
• Stacking in space and time: a flowering sequence is stacking along the calendar.
• Food forest, living mulch and macchia: plantings that flower in many layers.
• Chickens in the system: the other small animals of zone 2.

Pollinators at Sa Medada

Sa Medada is a slope in Jerzu, in Ogliastra on the east side of Sardinia, with mild winters and a dry season from roughly May to September. Several of the plants growing in the open there depend on insects, each in its own way. The avocado sets more fruit with bees and with cross-pollination between its flowering types. The cherimoya finds few insect visitors outside its homeland, which is why growers in Spain pollinate it by hand. Carpenter bees are the best pollinators of the purple passion fruit. The flowers of the fava bean, one of the nitrogen fixers in the ground, are much visited by bees. Among the plants grown in pots or partly planted out, the feijoa depends mainly on bees.

The macchia on the steeper slopes and the old olive grove frame these plantings.