by Dave Goulson
One clever way of getting a handle on this is to try what Marina has been doing in Argentina – use museum specimens, in this case from before 1990, and identify what pathogens they contain using genetic techniques to amplify pathogen DNA. This can then be compared to the pathogens found in the wild in North America today; anything that arrived with commercial bees should not have been present before 1990. Sydney Cameron’s lab at the University of Illinois have such work underway, so hopefully we may understand more about this within a year or two, though of course that would not provide us with any mechanism for solving the problem. Once a non-native species – be it a bee, a disease or a cane toad – has been released it is rarely possible to eradicate it, and this would certainly be impossible for a microscopic parasite.
So it was that I flew out to California in late April, on an interminable dog-leg journey from Glasgow to Amsterdam to Portland, Oregon, and finally south to Sacramento. It was a beautiful spring afternoon as we flew on the final leg of the journey, and although I was tired I had my nose pressed against the glass of the window. Portland looked like a green and pleasant city, bisected by the Columbia River, and surrounded by lakes and forests. As we headed south we quickly left civilisation behind and flew over wild and remote mountainous country, dense forests from which jagged snow-capped peaks rose. Even in late April the higher lakes were still frozen and carpeted with snow, etched white amongst the endless dark forests, which I imagined to teem with bears, moose and elk. As we continued south the land below dropped and became a little less rugged, with more settlements and more pale green pastures where the forests had been cleared. This, right beneath me, was the heart of Franklin’s country, centred on the rural town of Ashland in southern Oregon. Perhaps, somewhere amongst the myriad green valleys and forested peaks, a few surviving Franklin’s queens might be thinking about burrowing up from their hibernation chambers to meet the spring sunshine.
From Ashland, we passed over more wild, densely forested mountains, and over the 3,000-metre snowy volcanic peak of Mount Shasta in northern California. From there southwards the land dropped – the forests started to break up with homesteads visible, dotted amongst the trees, and patches of meadows, just as there were near Ashland. Then, suddenly, the forests ended abruptly and we were over a seemingly endless extent of pancake-flat arable land – the Central Valley of California, an 800-kilometre-long strip of flat, fertile land which runs due north to south, sandwiched between the Rocky Mountains to the east and the Californian coastal mountain ranges in the west. This is one of the most intensively farmed areas on Earth; the fields below resembled a chequerboard of greens and brown, most of them perfectly square with precisely aligned north–south and east–west boundaries with just the thinnest of fence lines to separate them. As the plane started to drop I could see that some of these huge fields were planted with regular rows of perfectly spaced fruit trees, but apart from these there appeared to be almost no trees, and precious little else in the way of natural habitat where wildlife might live – it looked rather bleak and depressing.
Davis is towards the northern end of the Central Valley, a few kilometres west of Sacramento. Despite my unfavourable first impressions of the Central Valley when coming in to land, Davis turned out to be charming – a sleepy university town, a world of sunshine, flip-flops, shady avenues, blue sky, pavement cafés and Frisbee games in the park. It seemed a million miles from Scotland as I explored on foot the following morning. The wide, tree-lined avenues are laid out on the usual regular grid but unlike most American towns, there were hardly any cars; nearly everybody seemed to be on bicycles. The few cars on the streets were driven very slowly: in Davis the pedestrians have right of way to cross at any time. As a result, I found exploring Davis on foot slightly trying; every time I paused on the pavement to get my bearings the cars would stop, thinking I wished to cross the street. If I hesitated, they would beckon me across, smiling encouragingly, and I would feel obliged to do so. I spent much of my time politely crossing backwards and forwards over the quiet, leafy streets.
I spent the next few days in Davis, giving my talks, chatting with Neal’s students, and finding out more about their work. Much of Neal’s efforts are focused on understanding how bees of different sorts use the landscape – where they nest, how close those nest sites need to be to crops for them to reach and pollinate them, and what other flowers aside from those of the crops they need to keep themselves going. In many ways it was similar to what my own research group had been doing for many years, but in a nicer climate and with different types of bee. There are a huge diversity of crops that need pollinating in the Central Valley – melons, apples, strawberries, peaches, nectarines, almonds, watermelons and many more. Yet the area is pretty inhospitable to bees, for it has been more or less entirely denuded of native vegetation, so there are few places for them to nest and few wild-flowers for them to feed on. One solution is for farmers to bring in lots of honeybee hives when a crop flowers – this is what the almond growers do – but it isn’t ideal. Honeybee hives are expensive to hire, and they are becoming increasingly hard to come by as honeybee colonies have been dying at unusually high rates in recent years. If the honeybee supply were to fail for some reason, such as an outbreak of disease, then the farmers would be in big trouble. In any case, honeybees aren’t particularly good at pollinating some crops, such as tomatoes and strawberries, so relying entirely on domesticated honeybees is clearly not the answer.
As a result of the high demand for pollinators and the shortage of bees in this impoverished landscape, California has become something of a hotbed for bee research. Mirroring Robbin Thorp’s career, for many years this work focused exclusively on honeybees – how best to breed them and provide a ready supply for wherever they were needed in California. In recent years, interest has turned to the benefits that other, wild pollinators can bring, as realisation has dawned that many of the other 4,000 or so species of bee found in North America are also useful pollinators. Some of Neal’s earlier work, carried out with Claire Kremen from the University of California in Berkeley, showed that farms near patches of wild habitat – which largely means farms near the edge of the Central Valley – benefited from wild pollinators spilling out from the natural vegetation to visit and pollinate their crops. Organic farms near the edge of the valley had no need to buy in honeybees at all, whereas those that used pesticides, and those that were in the centre of the valley, had to hire in honeybees or their crop yields suffered. What was more, farms near patches of wild habitat received more reliable pollination from year to year – relying on one pollinator species is risky because that bee might have a bad year, whereas if you have lots of different ones then every year at least one of them is likely to be doing well.
Of course farmers in the middle of Central Valley can’t just pick up their farm and move to the edge, and might feel envious of their valley-side neighbours, awash with bees as they are. One obvious solution to their situation might be to try to provide extra flowers and nesting sites for wild bees on the farms themselves, so that they are not reliant on there being wild areas nearby. This is what Neal’s team have been investigating – sowing strips of flower mixtures along field edges or right across the middle of fields, and planting woody hedges that can provide nest sites. The flower strips look beautiful – mixed shades of yellow and orange from sunflowers, lupins and Californian poppy, intermingled with the mauve of phacelia, and the results so far strongly suggest that, as one might have guessed, these strips do boost the wild bee population and improve crop pollination. What is more, there can be benefits that go far beyond encouraging bees. A recent field study by Richard Pywell’s research group at the UK’s Centre for Ecology and Hydrology revealed that setting aside 8 per cent of the crop area for flower mixes and other wildlife habitat resulted in not only an increase in the numbers of bees, but also increases in the abundance of predators of crop pest such as ground beetles, ladybirds and hoverflies. More compellingly, the yields of various c
rops increased steadily over the five-year period in the areas where the extra wildlife habitat was created, so that the farmer lost no yield by sacrificing 8 per cent of the land. Of course one should not extrapolate from Buckinghamshire to California, but nonetheless these kinds of studies argue powerfully that less can be more in farming. It might seem obvious that a farmer will get more yield if he plants a larger area with crops, but this clearly is not necessarily the case. Imagine if we could use these and similar studies to persuade farmers across the globe to incorporate significant patches of wildlife-friendly habitat on their farms, simultaneously reducing their need to use insecticides. Perhaps those vast crop monocultures of the Central Valley and the endless soya bean fields in Argentina would produce just as much food if there were strips of wildflowers and natural habitat spread across the plains.
While I was at Davis I had long chats with Robbin Thorp, and he showed me around Davis’s dedicated bee research facility, the grandly entitled ‘Harry H. Laidlaw Jr.fn3 Honey Bee Research Facility’, which lies at the end of ‘Bee Biology Road’ – I kid you not – on the outskirts of Davis. Robbin presents an imposing, Darwin-like figure – I would guess that he must be well into his seventies, tall, with a bushy white beard, albeit not yet quite as lavish as the great man’s became in later life. Half of the building is still devoted to honeybee rearing and research, with experimental hives indoors in the labs, but linked to the outside world by plastic pipes through which the worker bees rush back and forth. The remainder of the building was full of eager students, either trying to identify pinned specimens of wild bees or engaged in the tricky and time-consuming business of rearing Vosnesensky bumblebee nests, which would later be used in experiments. This is one of the most common Californian bumblebees, and the nests were destined to be placed out in fields with or without wildflower strips, to see how much the flowers benefited the survival and eventual reproduction of the bee colonies.
Outside, Robbin proudly showed me their Häagen-Dazs-sponsored ‘bee haven’, a garden filled with mainly native Californian flowers centred around an enormous ceramic bee on a plinth. The flowers were absolutely teeming with real bees of bewildering variety. Robbin was brimming with the knowledge that comes from decades of experience in the field, and he was able to identify most of them at a glance, while I was still trying to get to grips with distinguishing between the more common North American bumblebees. There were black-tailed bumblebees, Vosnesensky bumblebees, Van Dyke’s bumblebees, massive iridescent purple-black carpenter bees and numerous smaller mining and leafcutting bees – over 1,000 species of bee have been recorded in California, and it seemed to me that most of them were living here. As if the bees weren’t enough, hummingbirds also flashed through the shrubs, piping shrilly. Sadly, of course, there were no Franklin’s bumblebees. Robbin proudly showed me a black-tailed bumblebee nest in what looked like a tit box nailed to a tree. This species is closely related to our early bumblebee, and is just as docile, for the bees were quite unperturbed when we lifted the lid and had a quick peek inside.
Once I had done my duty in Davis it was time to go on an adventure. Northern California in the spring is an absolute joy for a naturalist; the winter rains mean that there are flowers and lush greenery everywhere, while from April onwards one can almost guarantee sun every day until October, except in the highest mountains. The region has extraordinary geological and climatic diversity. The mountains on the west coast are bathed in mists and fogs caused by the contrast between the icy ocean and warm air, and they support spectacular sequoia forests which I had been lucky enough to visit before. Further inland and heading east, these forests give way to Mediterranean scrub, then to the agricultural plains of the Central Valley, and finally to the mighty Rocky Mountains.
Although the old haunts of Franklin’s bumblebee are due north from Davis, I decided first to head north-west to the coastal mountain range, where the University of Davis has its own sizeable nature reserve. The McLaughlin Reserve comprises 7,000 acres of native Californian grassland and chaparral, habitats that have been all but entirely lost elsewhere. Paul, the reserve warden, was kind enough to take me on a tour. McLaughlin’s used to be a gold mine, but when the gold ran out the land was handed over to the University of California, perhaps because the area was of little use for anything else. Parts of the site are badly contaminated from the mining operation. Gold mining is one of the most environmentally damaging of industrial activities, and for every 0.3 ounces of gold – enough for one ring – about twenty tonnes of toxic waste contaminated with mercury and cyanide is produced. By all accounts the company that mined at McLaughlin were better than most at minimising the environmental damage, and most of the reserve area was not badly damaged by the mining. However, McLaughlin is unusual for it lies on serpentine rocks which are naturally rich in toxic metals. As a result, the soils contain high concentrations of magnesium and iron, which most plants cannot tolerate. Most native Californian grasslands have been lost to agriculture, but those that were not converted to farmland have suffered heavily from invasion by European grasses which seem to have taken well to the Californian climate and outcompete almost all else. The serpentine soils at McLaughlin offer some protection against these invaders. Over the millennia, a lovely selection of native flowers have adapted to thrive on these soils, and these communities have been less invaded by European weeds because the invaders struggle to cope with the high levels of metals in the soils. Nonetheless some do, and the invading species are themselves slowly adapting to the local conditions, so Paul fights an ongoing battle with these aggressive weeds.
With 7,000 acres to look after, hand weeding is clearly not an option, and so Paul reluctantly relies upon graminicides – herbicides that selectively kill grasses – to battle the incoming grasses. This is not ideal on a nature reserve, but it is hard to conceive of an alternative that would work on the scale needed with the very limited manpower available to him. Fortunately the native grass species seem to have a little resistance to these herbicides, and although they are knocked back by them they do not die out entirely. However one feels about the ethics of using pesticides on nature reserves, it seemed to be working. Paul showed me untreated areas with few flowers and dominated by rank, dry grasses, while nearby the restored, pesticide-treated grasslands were spectacular, filled with no less than four different species of lupins in blue, yellow and cream, plus the dramatic blue spires of wild delphiniums, all emerging from a carpet of delicate native yellow clovers.
We spent a pleasant day, checking on the status of the invading weeds and the restored areas, and crawling around in narrow creeks searching for red-legged frogs, a nationally endangered species for which there were unconfirmed sightings at McLaughlin which Paul was keen to verify. Of course I obsessively caught and identified any bumblebees that I saw with an optimistic eye to turning up a previously undiscovered population of Franklin’s bumblebee. We both failed – no Franklin’s or red-legged frogs – but I did find a nest of Californian bumblebees, the workers pouring from a crack in the dried earth which must have led down to an old rodent burrow. This species had not previously been recorded on the reserve, so I felt that this indulgent day pottering about looking for flowers, frogs and bees hadn’t been entirely wasted.
From McLaughlin I headed north – it was time to visit the old haunts of Franklin’s bumblebee. My route took me up the middle of the Central Valley along Interstate 5, through endless flat fields of crops in neat rows, and past thousands of acres of almonds. This isn’t the biggest almond-growing region in California – that is a little further south, closer to San Francisco – but it was still almond growing on a staggering scale. Farming in Britain, even in the arable heartland of the Fens, seems tinpot compared to this sort of industrial food production. Let me give you a few numbers – there are 800,000 acres of almond trees in California, producing 80 per cent of all the almonds grown in the world, about five billion dollars’ worth, or 700 billion individual almonds. That is a lot of nuts in
anyone’s book.
As in the agricultural belt west of Buenos Aires, it is questionable whether producing food in this way is desirable or sustainable in the long term. In California, their intensive farming system is putting huge strain on the environment, and the cracks are beginning to show, quite literally. Each individual nut requires about five litres of water to produce, so that almond farmers are currently using 3.5 billion cubic metres of water on their crops. Of course, most other crops also require lots of irrigation water – I drove past huge fields that had been flooded, creating vast, square, shallow lakes, so that the soil would be moist for sowing melons, corn, tomatoes, peppers and potatoes. We humans also use vast amounts of water in our homes, gardens and on our golf courses, and in California it hasn’t rained much in recent years, so that there just isn’t enough to go around. Some of the almond farmers have rights to a share of the dwindling supply of river water for irrigation, but others do not and have resorted to drilling boreholes deep into underground aquifers and pumping up the water. Well-drillers are rushed off their feet, and there is now a waiting list of over a year for their services. When before they had to drill down perhaps 150 metres to hit water, now they often have to drill twice as deep, which inevitably makes both the drilling and the pumping up of the water more expensive. It is also, of course, a worrying sign – the aquifer water, which may have sat there for thousands or even millions of years, is being depleted. There is no regulation or monitoring of how much water is pumped, or how many wells are dug, so this new Californian gold rush is living on borrowed time. This isn’t just a problem in California – across the USA, a jaw-dropping twenty-five cubic kilometres of water are pumped from the ground each year.
