Pollinating insects and insect-pollinated plants evolved together. It is obviously essential that the insects are active when the flowers are out, but is climate change causing problems? In other words, are bees (for example) becoming active before the flowers are ready for them? A group of scientists in Poland have tried to answer this question.
Bee Cleansing Flight
Honeybees, outside the tropics, spend most of their winter inside the hive with little opportunity to go outside to 'relieve themselves'! When the weather gets warm enough they leave the hive, and take the opportunity of a 'cleansing flight' (to defaecate). It has been observed that honeybees are leaving their hives to take their cleansing flights earlier than in the past.
This first cleansing flight marks the start of their busy summer season – when they visit flowers to collect nectar and pollen.
Nectar and Pollen
Honeybees rely on the energy-rich nectar that flowers produce for their day-to-day energy, and to store as honey to see them through the winter. Pollen is a good source of protein, and it is collected from flowers to feed the developing young back in the hive. Honeybees store both pollen and honey inside the hive - collected when the flowers are producing, and storing for the periods when they are not.
For flowering plants the pollen is not a 'luxury, energy-rich food', but their means of reproduction. Bees go from flower to flower collecting pollen for their own use, but in doing so they inadvertently transfer a few pollen grains from the 'male' parts of one flower to the 'female' parts of another. This process of reproduction by cross-pollination ensures the genetic well-being of the flowering plants.
Flowers produce nectar in order to lure bees (and many other pollinating insects) deep into their flowers so that the bees 'accidentally' get covered with pollen.
Obviously it is important that the pollinators are around when the flowers are ready - if they were not, then plant reproduction would be compromised!
Global Warming and Bees and Flowers
It is well-known that spring is coming earlier in temperate regions than it was in the historical past.
According to his sister's diary, Wordsworth's famous poem 'I wandered lonely as a cloud ...' records the 1802 flowering of daffodils on April 15. Alan Titchmarsh notes the daffodils flowering today in the same place do so in mid-March.
But the question is - how much earlier are the flowers? and how much earlier are the bees? If there is a mis-match then there could be serious problems ahead.
Fortunately the Polish scientists (Sparks, Langowska et al.) who have been studying this problem conclude that the earlier emergence of bees, and the earlier appearance of flowers: '... will not cause a pollination synchrony crisis.' This may be true at present, but further work will be needed to see if it will remain so in the future.
Source:
- 'Advances in the timing of spring cleaning by the honeybee Apis mellifera in Poland', Sparks, Langowska et al., Ecological Entomology, 2010: vol.35, issue 6.
