Plight of the humble bee

Global warming means spring is arriving sooner. As winter draws in that may sound attractive, but it means plants are flowering earlier than usual. If they become out of sync with nature’s pollinators, the consequences for the global economy could be serious.

Phenology is nothing new. It is the study of biological firsts — the arrival of the first swallow, the first bud or flower, the first leaf colouring and fall in deciduous trees. Since at least the late 18th century botanists have been logging seasonal events to help unlock the secrets of mother nature.

Now though, modern technology including remote sensors and satellites, is helping scientists see ever further and observe more closely. The pictures emerging are disturbing. Phenology is bearing witness to the earliest impacts of global warming and nature’s clock is running fast.

More than 1.4 billion jobs worldwide and three quarters of the world’s crops, worth £385 billion, rely on pollinators

One species of sedge in Greenland is now bursting into growth 26 days sooner than it did only a decade ago. This year spring arrived up to three weeks early in many parts of the US. Flower species there, such as wild geranium, have been recorded blooming 24 days earlier than in 1945.

In Britain studies suggest spring is now 11 days earlier than in the 19th century, with the first oak leaves, swallows or hawthorn flowers appearing a week and a half earlier than was recorded in 1890.

Based upon signs like the appearance of frogspawn and orange-tip butterflies, scientists say spring spreads from the southwest to the northeast of Britain. Between 1891 and 1947 the season moved up the country at around 1.2mph, travelling around 28 miles a day. Now it speeds across at 1.9mph, covering 45 miles a day.

Many of us in the north who hate the long, cold winters will guiltily welcome this news, knowing it to be too true to be good.

But one of the biggest dangers is that the delicate balance in the eco-system between plants and pollinators is knocked out of kilter.

Reproduction and survival

Flowering plants that produce seeds are known as angiosperms and are among the planet’s most successful and important life forms. More than 250,000 have been identified so far and just as many more may await recording.

Angiosperms require two processes to take place for successful sexual reproduction: pollination and fertilisation.

The sperm nuclei of the pollen have to be transferred from the anthers of a stamen (the male reproductive organ of a flower) to the pollen-receptive stigma of a pistil (the female reproductive organ, which contains the egg nucleus in the ovary).

Some plants self-pollinate — pollen transfer occurs within the same flower or among the flowers on a single plant, usually because the anthers touch the adjacent stigma.

The majority of flowering plants, however, depend on the transfer of pollen from other individuals — cross-pollination.

Some species manage this pollen transfer through wind and water, but three quarters of the world’s angiosperms rely on bees and other pollinators to meet their reproductive needs. Typically, they entice pollinators through the production of nectar. As the pollinators move from flower to flower in search of this high-energy food that fuels their own reproductive cycle, the plants dust them with pollen, which is then transferred from flower to flower.

The majority of pollinator species are wild, including more than 20,000 species of bees and some species of flies, butterflies, beetles, moths, birds, bats and other vertebrates. Of them all, bees are the most important pollinator — 90% of the world’s key economic crops are visited by them.

Pollination value

It is difficult to exaggerate the importance of pollination and pollinators.

A 2016 study by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) estimated that more than 1.4 billion jobs worldwide and three quarters of the world’s crops, worth £385 billion, rely to some extent on nature’s pollinators. Beyond food, pollinators also contribute directly to medicines, biofuels, fibres like cotton and linen, and construction materials. Globally nearly 90% of wild flowering plant species depend on animal pollination.

Scientists at the University of Reading’s Centre for Agri-Environmental Research (CAER), who contributed to the study, say that “insect pollination services” are worth over £430 million a year to the UK economy.

Without pollinators, crops such as coffee, cacao and apples would drastically suffer, and changes in global crop supplies could increase prices to consumers and reduce profits to producers, resulting in a potential annual net loss of economic welfare of up to £150 billion globally.

“Pollinators affect all of us,” says CAER’s director Professor Simon Potts. “Pretty much nearly all your fruits and many of your vegetables are pollination-dependent.”

“ We face a catastrophe in future years unless we act now. Wild pollinators need greater protection.”

Scientists fear that if flowers come into bloom before the bees and other pollinators are ready to set to work it could lead to severe depletion of yields in food crops. So how big is that risk?

The risk

Flowering plants and pollinators often co-evolved, timing their cycles to coincide — for example, insects maturing from larva to adult precisely when nectar begins to flow.

But scientists do not fully understand what environmental and genetic cues plants and pollinators use to manage this synchrony. Some pairs of plants and pollinators may respond to different cues, like light, soil or air temperature. It could be that an early spring for the plants brings forward the season for bees too, and there is evidence to suggest that is the case.

But there are other issues. One of the problems with early springs, as any gardener will testify, is the random sudden cold spell or frosty night.

Brood nest temperature is key to the health of a colony and is carefully controlled. Honey bees in a cluster in the hive work hard to keep the queen and the larvae at between 32 and 35 degrees Celsius. If the temperature is too high they fan the hot air out. If too low they eat lots of honey, uncouple their wings and contract and relax their flight muscles — think of it like shivering — to generate heat.

Bringing forward their cycle makes them much more vulnerable to cold spells. If they cannot create enough heat the eggs at the edge of the cluster may die, weakening the colony. If they have to start the whole three-week nesting process again it can put the pollinators and plants out of sync, reducing crop yields.

Even modest deviations in optimal brood temperatures are known to influence the health of the resulting adult bees, making them more susceptible to certain pesticides as adults.

Shrinking populations

Certainly there is concern about bee welfare. Data is poor but what is clear is that bee populations are shrinking — whether that is because of climate change, intensive agriculture or use of pesticides like neonicotinoids.These are particularly controversial as they are absorbed into the whole plant, rather than remaining on the surface and so the bees are believed to ingest the poison with the pollen.

In Europe, 9% of bee species are threatened with extinction and a further 5% are considered “near threatened”. Populations are declining for at least 37% of European bee species and the same drivers are suspected to be at work in Latin America, Asia, and Africa.

The CAER team compared the numbers of active beehives to the demand for pollination services across 41 European countries, and mapped the changes between 2005 and 2010. They found:

—         In more than half of European countries (including the UK, France, Germany and Italy) there were not enough honeybees                to properly pollinate the crops grown.

—         The problem was particularly acute in Britain, which has only a quarter of the honeybees it needs to pollinate crops.

—         Europe as a whole only has two thirds of the honeybee colonies it needs, with a deficit of more than 13.4 million colonies.

Professor Potts said: "We face a catastrophe in future years unless we act now. Wild pollinators need greater protection. They are the unsung heroes of the countryside, providing a critical link in the food chain for humans and doing work for free that would otherwise cost British farmers £1.8 billion to replace.

"We need a proper strategy across Europe to conserve wild bees and pollinators through habitat protection, agricultural policy and farming methods — or we risk big financial losses to the farming sector and a potential food security crisis."

There is a lot that can be done to support our valuable pollinators, but one thing that is going to be hard to change now is the weather — something to think about when you are enjoying the early spring sunshine next year!