Bees and biodiversity


  • Author: Leila Battison
  • Date: 17 Aug 2015
  • Copyright: Wikimedia Commons - Image appears as courtesy under CC-BY-SA-4.0 licence

In the past decade, there has been growing concern over the numbers of bees buzzing around our countryside. Bees are one of the major groups of insects responsible for carrying pollen from one plant to another to ensure the growth of fruit or the healthy sexual reproduction of crops. Scientific studies, news articles, and environmental campaigns have highlighted the critical need for these busy pollinators in order to sustain natural biodiversity and maintain our global food supplies.

Bees are responsible for pollinating a staggering 150 different crop plants, including the clover and alfalfa on which the beef and dairy industries rely. They are essential for the reproduction of twelve widespread crops, such as Brazil nuts and pumpkins, and together contribute to $15 billion of crop farming in the United States alone. In the Central Valley of California, endless rows of almond trees are accompanied by stacks of honeybee hives and the gentle hum of a huge workforce of tiny laborers; this industry is the most reliant on bee pollination worldwide.

thumbnail image: Bees and biodiversity

So, when the first reports of a decline in bee numbers began to emerge in 2006, alarm bells rang out for these interdependent plant populations. Without the bees, how can the huge farming industries be sustained? What is causing the loss? And now, nearly ten years after issue was first recognized, can we predict its ultimate effects? Is it too late to fix the problem?

Various purportedly unbiased studies have attempted to divine the cause of the decline in bee populations. In 2010, a team led by French scientist Cedric Alaux published in Biology Letters [1], claiming that the loss of bees was linked to the already severe loss of biodiversity caused by the expansion of human settlements and industry. With fewer wild plant species to feed on, the bees' immune systems become compromised and as a result, they are much more susceptible to diseases which, decades ago, they would have been able to shrug off. Today, it is widely recognized that a complex interaction of factors can lead to the loss of bees within managed hives, in a phenomenon that is now termed 'Colony Collapse Disorder'. Pathogens, including various fungi, parasites and viruses, can move rapidly through tightly packed hives, while synthetic chemicals such as neonicotinoid pesticides can also directly harm the insects [2]. Additionally, the ever-intensifying pressure for bee-pollinated crops, product-maximizing beekeeping practices, and the complex effects of climate change all act to negatively exploit the overworked colonies.

Estimating Bee Numbers

But just how sure can we be that the bees are in decline? The alarming reports of declining numbers require some hard statistical data to support them, but it is more likely that the average person is more likely to run squealing from a group of bees, or swat them away, than count them. However, it is not necessary to get up-close and personal in order to estimate bee numbers. For bees kept in hives, there's a nifty calculation based on the numbers of bees returning to the hive in a minute, the estimated time for a return journey, and the number of frames (honeycomb-supporting structures) in the hive. Alternatively, a direct measurement of the mass of a colony, minus estimations of frame and comb mass, can give a ballpark figure of population if you know the mass of a single bee. Repeat these calculations at appropriate intervals, and there’s your data.

Counting wild bees and solitary bee species is somewhat more problematic, as there may be no accessible hive with observable bee traffic, and one rapidly moving bee looks very much like another. In these cases, then, more time-consuming methods must be used, such as the classic ecological mark-recapture technique, which samples portions of a population within a given area on two successive visits to estimate overall population size. This method is riddled with caveats and assumptions, but again, if the same assumptions are made among all measurements, then reliable comparisons may be made between datasets. As this approach requires considerable manpower and time, especially for such small animals, modern studies have made use of so-called ‘citizen science’ to collect vast quantities of data over large areas. One such scheme in the UK, the ‘Great British Bee Count’ [3], organized by Friends of the Earth, encouraged members of the public to identify and log bees within their own gardens and allotments, even providing a user-friendly app to keep track of bees. The large datasets collected in this way have already led to new discoveries of bee population distributions [4], and in time can be collated to give valuable time series.

We are unable to say ‘Bees are killed by X, so we should stop X’, and so this critical threat to biodiversity and food security still advances unaddressed. It is clear that additional data and meta analysis are required to isolate the most significant factors, and perhaps we should adopt a precautionary principle and take action to protect, not exploit, our planet’s biodiversity before we reach a point of no return for our overstretched insect workforce.

Employing different data collection techniques over various areas and timescales, a range of scientific studies have produced contrasting results. For example, a study in 2009 [5], making use of historical data, indicated that the global population of bees has actually increased by 45% since the 1960s, but has been outstripped by the fourfold expansion of pollinator-dependent crops. Meanwhile, a recent study of 16% of all managed honeybee colonies in the United States (6) revealed that bee numbers have dropped by 42% in the last year alone, with summer declines greater than those of winter for the very first time. Yet, while these losses seem drastic, they are less extreme than the initial declines ten years ago.

Wild Bees

Most reports of bee decline have focused on the major losses occurring in managed honeybee hives, and the associated impacts on the crops that depend on them. However, an increasing number of studies have also begun to recognize the importance of wild bee species and other pollinators, which can be more than two times as effective as managed colonies. A study published in Science [7] in 2013, based on data from 40 crop types in 600 fields worldwide indicated that these groups of insects, many of which are solitary and depend on natural biodiversity, have also shown a major decline over the last decade, most likely as a result of habitat loss from urban expansion. Further, historical data has revealed [8] that around half of the 109 wild bee species in the United States went extinct during the 20th Century, again linked to the loss of forests.

In Europe, large solitary bumblebees are among the top pollinators, contributing up to €22 billion to agriculture annually. However, according to the International Union for the Conservation of Nature in 2014 [9] nearly a quarter of Europe’s bumblebees face extinction, and yet still little is known about bumblebee disease. Without the high population density of an enclosed hive, colony collapse disorder is unlikely to have a direct effect, however bee numbers could still be directly linked to climate change, the intensification of agriculture, and changes in farming land uses.

Is it too late?

Studies of bee populations have unequivocally shown a consistent decline over the last decade, regardless of country, species, or crop. With a lack of true understanding of the causes, this loss can be expected to continue, and the long-term effects on natural and agricultural biodiversity are difficult to predict. With the large-scale loss of pollinators, crop yields will drop, leading to the inflation of certain food prices and the outright loss of certain foods. As part of their ‘Share the Buzz’ campaign in 2013, Wholefoods supermarkets removed from their shelves all the products that are dependent on these at-risk pollinators, providing a striking image of the huge impact this decline will have; they removed 52% of their normal product mix [10]. The impacts are not limited to vegetable products, either. Owing to the dependence of the meat and dairy industry on bee-pollinated clover and alfalfa, we risk the loss of beef, milk, and their derivatives from our weekly shop.

But is it too late to save our bees and our bee-dependent lifestyle? What can we do to halt the decline and reverse the effects? Organic farms provide forage as food for bees and generally employ less intensive agricultural methods to prevent the pollinators from being ‘overworked’. But, as prices of organic goods in supermarkets demonstrate, this is an expensive and potentially unsustainable approach to global food production for over seven billion people.

In general, there are difficulties in promoting awareness and action against the loss of pollinators, due to the lack of clear cause and effect. As the bee decline is linked to the complex interaction of multiple factors, there is no definite course of action for policy-makers, while the voting public also crave simple links and simple solutions. We are unable to say ‘Bees are killed by X, so we should stop X’, and so this critical threat to biodiversity and food security still advances unaddressed. It is clear that additional data and meta analysis are required to isolate the most significant factors, and perhaps we should adopt a precautionary principle and take action to protect, not exploit, our planet’s biodiversity before we reach a point of no return for our overstretched insect workforce.












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