The Ecological Importance of Bees

A. Sometime in the early Cretaceous period of the Earth's history, hunting wasps of a certain type became bees by adopting a vegetarian diet: they began to rely more and more on the pollen of plants as a source of protein for themselves and their offspring, as an alternative to insects. In so doing, they accidentally transported pollen on their bodies to other plants of the same species, bringing about pollination. The stage was thus set for a succession of ever-closer mutual adaptations of bees and flowering plants. In particular, flowers began to reward bees for their unwitting role in their reproduction by providing richer sources of pollen and another source of nutrition, nectar.

B. Today about 15 per cent of our diet consists of crops which are pollinated by bees. The meat and other animal products we consume are ultimately derived from bee- pollinated forage crops, and account for another 15 per cent. It follows that around one third of our food is directly or indirectly dependent on the pollinating services of bees. On a global basis, the annual value of agricultural crops dependent on the pollination services of bees is estimated at £1,000 million (US$1,590 million). Much of this pollination is due to honey bees, and in monetary terms it exceeds the value of the annual honey crop by a factor of fifty.

C. But the apparently harmonious relationship between bees and plants conceals a conflict of interests. Although flowers need bees and vice versa, it pays each partner to minimise its costs and maximise its profits. This may sound like an extreme case of attributing human qualities to non-human species, but using the marketplace and the principles of double-entry book keeping as metaphors may give US some insights into what is really going on between bees and flowering plants. In the real world, both flower and bee operate in a competitive marketplace. A community of retailers, the flowers, seek to attract more or less discriminating consumers, the bees. Each flower has to juggle the costs and benefits of investing in advertising, by colour and scent, and providing rewards, nectar and pollen, clearly a species which depends on cross-pollination is on a knife-edge: it must provide sufficient nectar to attract the interest of a bee, but not enough to satisfy all of its needs in one visit. A satiated bee would return to its nest rather than visit another flower. The bee, on the other hand, is out to get the maximum amount of pollen and nectar. It must assess the quality and quantity of rewards which are on offer and juggle its energy costs so that it makes a calorific profit on each foraging trip. The apparent harmony between plants and bees is therefore not all that it seems. Instead, it is an equilibrium based on compromises between the competing interests of the protagonists.

D. This sounds remarkably like the ideas of the 18th-century economist Adam Smith. In his book, The Wealth of Nations, Smith postulated that in human society the competitive interactions of different ‘economic units' eventually resulted in a balanced, or ‘harmonious’ society. One might predict, therefore, that economists would find the relationships between bees and plants of some interest. This is the case in Israel, where economists are collaborating with botanists and entomologists in a long-term study of the pollination biology of the native flora, in an attempt to understand the dynamics of the relationship between communities of bees and plants.

E. This sort of study is of more than passing academic interest. It is important that authorities understand the dynamic relationships between plants and their pollinators. This is especially true when, say, devising conservation policies. A good example comes from the forests of tropical South America. Here, as in all rainforests, there is a high diversity of tree species. There may be more than 120 per acre, but in a given acre there may only be one or two individuals of any one species: These trees are pollinated by large, fast-flying bees. There is evidence that certain types of bees learn the distribution of these scattered trees and forage regularly along the same routes. This is called ‘trap-lining’ and the bees forage for up to 23 km from their nests. The bees are therefore acting as long distance pollinators.

F. An issue of current concern in tropical forest conservation is that of trying to estimate the minimum sustainable size of islands' of forest reserve in areas where large-scale felling is taking place. There is much discussion on seed dispersal distances. But this is only one half of the equation, so far as the reproduction of trees is concerned. There is another question that must be addressed in order to calculate whether proposed forest reserves are close enough to the nearest large tract of forest: ‘what is the flight range of these long-distance foragers?' We need to know much more about bees and their relationships with plants before this question can be answered.

G. Bees, then, are vital to our survival. Furthermore, much of the visual impact of human environments derives from vegetation, and most vegetation is dependent on bees for pollination. Thus, as pollinators of crops and natural vegetation, bees occupy key positions in the web of relationships which sustain the living architecture of our planet.

Pacific navigation and voyaging

How people migrated to the Pacific islands

A. The many tiny islands of the Pacific Ocean had no human population until ancestors of today’s islanders sailed from Southeast Asia in ocean-going canoes approximately 2,000 years ago. At the present time, the debate continues about exactly how they migrated such vast distances across the ocean, without any of the modern technologies we take for granted.

B. Although the romantic vision of some early twentieth-century writers of fleets of heroic navigators simultaneously setting sail had come to be considered by later investigators to be exaggerated, no considered assessment of Pacific voyaging was forthcoming until 1956 when the American historian Andrew Sharp published his research. Sharp challenged the ‘heroic vision’ by asserting that the expertise of the navigators was limited, and that the settlement of the islands was not systematic, being more dependent on good fortune by drifting canoes. Sharp’s theory was widely challenged, and deservedly so. If nothing else, however, it did spark renewed interest in the topic and precipitated valuable new research.

C. Since the 1960s a wealth of investigations has been conducted, and most of them, thankfully, have been of the ‘non-armchair’ variety. While it would be wrong to denigrate all ‘armchair’ research - that based on an examination of available published materials - it has turned out that so little progress had been made in the area of Pacific voyaging because most writers relied on the same old sources - travelers’ journals or missionary narratives compiled by unskilled observers. After Sharp, this began to change, and researchers conducted most of their investigations not in libraries, but in the field.

D. In 1965, David Lewis, a physician and experienced yachtsman, set to work using his own unique philosophy: he took the yacht he had owned for many years and navigated through the islands in order to contact those men who still find their way at sea using traditional methods. He then accompanied these men, in their traditional canoes, on test voyages from which all modern instruments were banished from sight, though Lewis secretly used them to confirm the navigator’s calculations. His most famous such voyage was a return trip of around 1,000 nautical miles between two islands in mid­ocean. Far from drifting, as proposed by Sharp, Lewis found that ancient navigators would have known which course to steer by memorizing which stars rose and set in certain positions along the horizon and this gave them fixed directions by which to steer their boats.

E. The geographer Edwin Doran followed a quite different approach. He was interested in obtaining exact data on canoe sailing performance, and to that end employed the latest electronic instrumentation. Doran traveled on board traditional sailing canoes in some of the most remote parts of the Pacific, all the while using his instruments to record canoe speeds in different wind strengths - from gales to calms - the angle canoes could sail relative to the wind. In the process, he provided the first really precise attributes of traditional sailing canoes.

F. A further contribution was made by Steven Horvath. As a physiologist, Horvath’s interest was not in navigation techniques or in canoes, but in the physical capabilities of the men themselves. By adapting standard physiological techniques, Horvath was able to calculate the energy expenditure required to paddle canoes of this sort at times when there was no wind to fill the sails, or when the wind was contrary. He concluded that paddles, or perhaps long oars, could indeed have propelled for long distances what were primarily sailing vessels.

G. Finally, a team led by p Wall Garrard conducted important research, in this case by making investigations while remaining safely in the laboratory. Wall Garrard’s unusual method was to use the findings of linguists who had studied the languages of the Pacific islands, many of which are remarkably similar although the islands where they are spoken are sometimes thousands of kilometres apart. Clever adaptation of computer simulation techniques pioneered in other disciplines allowed him to produce convincing models suggesting the migrations were indeed systematic, but not simultaneous. Wall Garrard proposed the migrations should be seen not as a single journey made by a massed fleet of canoes, but as a series of ever more ambitious voyages, each pushing further into the unknown ocean.

H. What do we learn about Pacific navigation and voyaging from this research? Quite correctly, none of the researchers tried to use their findings to prove one theory or another; experiments such as these cannot categorically confirm or negate a hypothesis. The strength of this research lay in the range of methodologies employed. When we splice together these findings we can propose that traditional navigators used a variety of canoe types, sources of water and navigation techniques, and it was this adaptability which was their greatest accomplishment. These navigators observed the conditions prevailing at sea at the time a voyage was made and altered their techniques accordingly. Furthermore, the canoes of the navigators were not drifting helplessly at sea but were most likely part of a systematic migration; as such, the Pacific peoples were able to view the ocean as an avenue, not a barrier, to communication before any other race on Earth. Finally, one unexpected but most welcome consequence of this research has been a renaissance in the practice of traditional voyaging. In some groups of islands in the Pacific today young people are resurrecting the skills of their ancestors, when a few decades ago it seemed they would be lost forever.