by Dave Goulson
Buff-tailed bumblebees, familiar and beloved natives of Europe which were recently voted the UK’s favourite insect in an online poll, have also been moved to far-flung lands, even more so than ruderal bumblebees. Buff-tails are widely used for tomato pollination, and are bred in huge numbers – about two million nests per year – in factories in Europe from where they are distributed all over the world. Along with ruderals, they were introduced from Kent to New Zealand in 1885 to help with clover pollination, and in 1991 they spread to Tasmania, probably with a little unofficial help from a tomato grower. In about 2005 they accidentally escaped from tomato glasshouses in Japan and are now thriving in the wild and spreading, causing great concern to conservationists. Potentially most disastrously, the Chileans decided to get in on the act and so they also imported buff-tails in 1998, presumably not satisfied with having just one non-native bumblebee species. It isn’t clear what role the buff-tails were supposed to perform in Chile – they are no good at pollinating red clover since their tongues are too short, but perhaps they were intended to pollinate tomatoes.
Whatever their intended purpose, the buff-tails didn’t stick around to find out. They are highly adaptable creatures, without doubt the most roughty-toughty European bumblebee species, able to survive in almost any habitat, including the most intensively farmed land, and naturally ranging from the semi-deserts of Morocco in the south to Norway in the north and Israel to the east. They rapidly came to terms with their new environment in Chile and set out to explore, multiplying as they spread. Buff-tails are a short-tongued bumblebee, so they tend to feed on rather different, shallower flowers than the long-tongued ruderal bumblebees and dahlbomii. These flowers are naturally pollinated by many hundreds of native Andean solitary bee species, mostly smallish creatures with short tongues about which precious little is known, and which may or may not be suffering from the presence of this new competitor. Buff-tails are also reasonably adept at nectar-robbing, stealing nectar from deep flowers when the need arises by biting holes in the back or side of the flower, so there are few flowers from which they cannot feed.
In 2006, eight years after they were introduced to Chile, the first buff-tails arrived in Argentina, following the trails of the ruderals through the mountain passes to San Martin. They quickly became enormously abundant, and to Carolina’s consternation the other bumblebee species both more or less immediately disappeared. Bombus dahlbomii, once the only bumblebee in the area and a common sight in summer, seemed to vanish, along with the vast majority of the ruderal bumblebees. Around San Martin and Bariloche, this has remained the case ever since. Carolina has seen just a handful of dahlbomii in the last nine years, and fears that they could go locally extinct at any time.
It was tales of this dramatic decline in the abundance of the world’s largest bumblebee that drew me to Argentina. There were major questions that seemed to be unanswered. What was causing the decline of dahlbomii? Was it competition with the invader, or was something else going on? How far had buff-tails spread, and were they wiping out native bumblebees wherever they arrived? Could anything be done to salvage the situation?
So it was that, on the morning of 2 January 2012, Jess and I arrived in Buenos Aires, jet lagged and bleary-eyed. The ancestors of dahlbomii had arrived in Argentina perhaps ten million years ago, the ruderal bumblebees eighteen years before us, while the buff-tails had been here for just six years at the time. We hired a car and set off to see which bees we could find. Buenos Aires is on the east coast of Argentina, on the south side of the mouth of the River Plate. Our broad aim was to drive due west to Mendoza, in the foothills of the Andes about 1,300 kilometres north of San Martin, and then to drive southwards towards San Martin, searching all the time for bumblebees. No one knew how far north or east the buff-tails had spread, since there are very few entomologists in Argentina. We knew we must hit their advance guard at some point along our route. In the meantime, we wanted to record any other bumblebees that we could find. Seven bumblebee species are said to be native to Argentina in addition to dahlbomii, but very little is known about their distribution and less still about their ecology.
Leaving Buenos Aires turned out to be harder than expected. The only road from the airport that we could find headed due north into the city centre. At that stage we had not managed to acquire a map, so we had little to guide us and became hopelessly lost trying to find a road west in a bewildering maze of streets thronged with battered, smoking cars of ancient vintage, gleaming new 4x4s, horse-drawn carts and the occasional goat. There were no signs to help us, few road markings, and dangerously deep potholes even in some of the larger roads. The local driving style seemed to involve considerable flexibility with regard to the rules of the road, if indeed there were any, with cars weaving past us on both sides, swerving erratically to avoid potholes, domestic animals and each other. Right of way seemed to belong to the person going fastest or with the most dilapidated vehicle, which meant it never belonged to me. It was altogether a nerve-shredding experience. Fortunately, the locals did not seem to mind my hesitant and slow progress, for not once did we get hooted at despite many near-collisions. I soon completely lost my sense of direction, and asked Jess to try to work out which way was west from the position of the sun. This was rather tricky since it was about midday in mid-summer, so the sun was very nearly vertically above us, but she did her best. Somehow, after an extensive tour of the affluent tree-lined boulevards of downtown and countless circuits of the less salubrious parts of the city, we emerged on the right road sometime in mid-afternoon, and began our journey west.
As soon as we left the urban sprawl, we entered the largest soya bean field I have ever seen. Argentina is one of the world’s biggest exporters of agricultural products, producing roughly one quarter of all the world’s soya beans and 5 per cent of its beef. Buenos Aires is surrounded by a vast, flat, fertile plain which stretches unbroken for 800 kilometres to the west, covering roughly 500,000 square kilometres, more than twice the total area of the UK. Technically it consists of many thousands of huge rectangular fields, rather than just one, but because they are separated by the narrowest of fence lines with no hedges and very few trees, the appearance was of one vast field that went on for ever. Giant silver silos for bean storage reared up at intervals on the skyline, which was otherwise unbroken. It is an impressive example of man’s ability to dominate nature, to eradicate pests and weeds and grow a single crop at the expense of all else. It was interesting to see the use of genetically modified crops being boldly advertised. In Europe, GM crops are regarded with deep suspicion, often labelled ‘Frankenstein’ crops in lurid tabloid headlines. Here, the roadside fences carried large placards shamelessly proclaiming the particular variety of GM crop that formed the sea of green beyond. I am told that most of these soya beans are shipped halfway around the globe to China where they are used to feed beef cattle or power biofuel plants. As I gazed over this vast expanse of uniform green, I couldn’t help but reflect that it ought not to be beyond our wits to devise less environmentally damaging and more efficient ways of using our world’s precious resources.
I generally love to visit new countries, largely because of the opportunity to see wildlife and landscapes I have not encountered before, but there was little to enjoy here. For a biologist this region of eastern Argentina was rather depressing – it can be no surprise that the bellicose bumblebee has disappeared, along with almost everything else that presumably used to live here. Clearly pesticides were heavily used because the few streams we crossed were devoid of fish, amphibians or the predatory birds such as herons and egrets which one might expect to see in abundance in the subtropics. All of the streams had been canalised into straight channels, often lined with concrete, and most were little more than running sewers, stinking and lifeless. Clearly the same crop was grown year after year on the same soil, rather than using any type of crop rotation, which meant that artificial fertilisers had to be poured on in bucketloads, which then added to the pollution of
the streams, causing blooms of toxic algae. The few towns we passed through were mostly dismal, dusty places, consisting largely of farm machinery sales and repair shops and agrochemicals merchants.
I couldn’t help but wonder what this land had once looked like, before man turned it over to his exclusive use. The fertile soils suggest that it may have supported a dense, subtropical forest, which presumably would have contained all sorts of interesting creatures. Of course we humans need to eat, and farmers need to make a living, but it seemed a terrible shame that there is nothing whatsoever left of what must once have been an immense forest.
To be fair, there were a few interesting highlights. On our second day driving across this endless plain we stopped for lunch in the shade of some Australian gum trees incongruously planted by the roadside, from the branches of which were suspended several huge, colonial nests of green parakeets – tremendously raucous, noisy birds which peered down at us curiously. One particular species of dragonfly seemed to have developed resistance to the pollution in the streams and had proliferated, their wings shimmering in the sunshine as they hawked across the road. It was impossible not to hit them as we drove by, and small brown birds of prey which we eventually identified as chimango caracaras sat by the roadside feeding on the ready supply of dragonfly corpses. Near the towns, dead dogs were frequent and their swollen corpses often attracted the much larger southern crested caracara – impressive and ferocious-looking Lewis Carroll caricatures of birds, eagle-sized beasts with crested heads, bald red faces and disproportionately long lemon-yellow legs. They were not alarmed in the slightest by our passing and stared at us challengingly with unblinking orange eyes.
Since we were supposed to be looking for bumblebees, we stopped every eighty kilometres or so along our route to hunt for them, doing one-hour timed searches as I had done previously in many other places, such as on Salisbury Plain and in the Gorce Mountains of Poland. We chose spots to search where there were at least a few roadside weeds, usually patches of yellow star thistles, creeping thistles and teasel, all of which are non-native plants which were presumably accidentally introduced by early settlers. Try as we might, we could find no bumblebees of any sort, although honeybees were often abundant and we occasionally found huge black carpenter bees, which I briefly got excited about in the hope that they were the black bumblebee Bombus atratus. These magnificent but slightly fearsome insects are the size of bumblebees, jet black with an oily purple sheen, but are actually solitary bees and despite the superficial resemblance are only distantly related to bumblebees.fn3
Towards the end of our second day of travelling west, the land slowly began to look a little less fertile, the crops less vigorous and more patchy. My GPS told me that we had been imperceptibly climbing as we travelled, and had now reached about 2,000 feet in altitude, although we had not seen anything that could remotely be described as a hill. The traffic had become steadily less frequent, so that now there was often no other vehicle in sight. After the town of San Louis the arable belt suddenly ended, and before us stretched an endless plain of low, spiny scrub, the arrow-straight and empty road ahead the only mark that man had made upon the landscape. It was a dramatic change after the intensive farmland, although no less monotonous in appearance. We stopped and stretched our legs, wandering amongst the thorny waist-high acacias. Insects abounded; tiny native bees swarmed over the few shrubs that were in flower, and a diversity of beetles scurried along the stony ground. The silence was broken only by staccato bursts of song from cicadas, endearingly ugly, bulbous-headed insects which perched among the twiggy scrub. Black vultures circled overhead, presumably hoping that we might expire. In the distance, we could see small tornadoes marching across the plain, twisted spirals of wind lifting dust and leaves high into the sky.
We continued westwards, the lack of any landmarks or bends in the road making it sometimes feel as if we were not moving at all. Every eighty kilometres we repeated our search for bumblebees. This was now much more fun as there were plenty of new insects to see, but there were no bumblebees to be found. We holed up for the night in a small town called La Paz which unexpectedly appeared ahead of us. I couldn’t imagine what its inhabitants did for a living. After La Paz the landscape became a little greener, and a few brave souls had tried to carve out fields and plant vineyards along the roadside, though none looked very productive. The road continued to climb very gently, and as it did so the vineyards became more prosperous, larger, neatly maintained, and with healthy rows of vines marching across the landscape. A blue-grey bank of cloud hung on the western horizon directly ahead. The map suggested that we should be nearing the Andes, but the landscape still appeared to be more or less featureless. As we approached the city of Mendoza, the cloud bank grew taller and began to gather texture, folds and shadows. Jess and I realised almost simultaneously that it was not a cloud bank at all, but an abrupt line of vast mountains, their tops sheathed in clouds. We stopped and spent a while gaping and taking pictures that utterly failed to capture the grandeur of the scene. At this point along their length the Andes are at their highest; Aconcagua, the highest mountain in the Americas, is just a smidge under 7,000 metres tall.
Mendoza nestles in the foothills of these mighty peaks, and is the centre of Argentina’s wine-growing region, rightly famed for its juicy, rich Malbec reds. Vines thrive on the cool mountain slopes, watered by the snow melt that pours down in spring from the ice-capped mountains above. By the time we arrived in Mendoza we had driven about 1,100 kilometres and conducted about fifteen entirely fruitless one-hour searches for bumblebees. We were starting to wonder whether there were any native Argentinian bumblebees left, and if so, where they were to be found. Most bumblebees prefer cool climates, so our next logical move was to try to get high up into the Andes. Old museum records suggested that dahlbomii used to occur this far north, and that there should be several other species present. West from Mendoza, we found an unsurfaced track which switchbacked up into the mountains. The vegetation changed from vineyards to semi-desert rocky slopes dotted with barrel-shaped cacti, and then to more lush, sub-alpine scrub. As we slowly approached Aconcagua the sky grew darker, and lightning flickered amongst the leaden clouds which shrouded its peak. It was here that Jess finally spotted our first South American bumblebee. It was a queen of Bombus opifex, a sizeable, largely yellow bumblebee with a reddish bottom. She was feeding on a yellow star thistle and quite unconcerned by our presence so we sat and admired her while the thunder rumbled overhead. Hunting around amongst the shrubs, we quickly found more opifex, mostly workers, many of them feeding on thistles of one sort or another. Later, as we followed the road up to 2,000 metres altitude, we entered an area where wild snapdragons were abundant, and these too the opifex seemed to love.
We spent that night in the small town of Uspallata, a pleasant, low-key tourist base for hiking in the high mountains and rafting on the tumbling rivers. We celebrated with a bottle of ‘Andes’ beer – in the circumstances it seemed rude not to – followed by a delicious steak each and a bottle of local red wine.fn4 It was surprisingly warm given the altitude and we sat outside to eat, watching iridescent green hummingbirds darting among the purple blossoms on the trees lining the street while Aconcagua brooded above us. It was a thoroughly pleasant evening.
The next morning we headed further into the mountains, to the border with Chile at nearly 3,000 metres altitude. We were hoping that we might find populations of dahlbomii this far north in the cool of the high mountains, but search as we might we found none. We did find a few more opifex at intervals, many of them feeding on a pretty pink daisy which grew in dense, silver-leaved clumps. Storm clouds plagued us all day, often catching us out in the open with our nets, drenching us in huge icy drops of rain. Towards the end of the day we headed back to Mendoza, and from there began the southward leg of our 6,000-kilometre journey, towards San Martin. Over the next few days we followed the main route south, which ran along the flatter land to the east of the Andes past affluent
bodegas and lush fields of vines and apple orchards. Wherever the opportunity presented itself we detoured west back up into the mountains to search for bees, subjecting our poor hire car to a thorough battering on the rough tracks. In large part the mountains were heavily grazed by vast herds of goats, tended by gauchos on horseback and wearing traditional costume: broad-brimmed hats, ponchos and spectacularly voluminous trousers. I remembered learning about gauchos in geography lessons at school – I spent hours drawing one, as I recall – but I’m sure we were taught that they herded something more manly than goats. We pondered whether they had dressed up especially for the tourists, but this seemed unlikely given that we were apparently the only visitors to these remote mountain valleys. The goats had clearly eaten most of the flowers and we found few bees, although there were a few isolated populations of opifex as far south as the rural market town of Malargüe, some 300 kilometres from Mendoza.
