The Attack of the Killer Rhododendrons Page 4

  The Netherlands is not a really big place. Even so, we got to see an awful lot of water and this was contaminated by an incredible assortment of introduced aquatic species. These include clawed frogs from Africa, water ferns from Brazil, Pacific crabs from Japan, round gobies from Russia, tubenose gobies from Germany, slipper limpets from the U.S., pond turtles from Italy, Wels catfish from Hungary, and soft-shelled clams from Canada.

  The Wadden Sea is 500 kilometres of coastal waters stretching northeast from Den Helder in the Netherlands, past Germany, and on to Denmark. It is a region of low-lying islands, sandbanks, and mud flats, and long recognized as home to incredible biological diversity, making it a sought-after refuge for citizens looking for an unspoiled corner of Europe. Those with a commercial mind think of it as an important nursery for edible North Sea marine life.

  In the 1800s, the Wadden Sea had a thriving oyster fishery based on the native European oyster. But, as so often happens, the harvest was a bit too zealous, and the fishery collapsed. Over the years attempts were made to find ecological replacements for the native oyster, including the American oyster and the Portuguese oyster, but these efforts met with failure. Then came the new kid on the block.

  In biology circles, the Pacific oyster has a rather nasty reputation for being where it shouldn’t be, including the Wadden Sea. Around sixty countries have reported it in their coastal waters, and it has become well established in at least twenty-four. In countries including Australia, Canada, Chile, and the Netherlands, the Pacific oyster is considered to be invasive, having a negative impact on the ecosystem and/or the economy.

  The Netherlands has long been a seafaring nation, and Pacific oysters have probably been arriving in the Wadden Sea for centuries, attached to the hulls of ships. For reasons not fully explored, these oysters didn’t establish themselves. Then they were introduced intentionally in the hopes of re-establishing the oyster fisheries where their American and Portuguese counterparts could not. The Pacific oyster followed a pattern typical of the establishment of introduced species; their numbers remained low for a protracted period before rapidly growing in quantity and distribution. Today there are more than 60,000 tonnes of Pacific oysters living on the Wadden Sea’s tidal flats. Thirty years after first being reported as a self-sustaining species, their numbers in the Netherlands show no evidence of levelling off.

  Pacific oysters are filter feeders, extracting plankton and organic material from the water with great efficiency. We are most familiar with them in their adult form, with two hard shells hinged along one side. But like others of their kind, very young Pacific oysters first spend three or four weeks as tiny free-swimming larvae before settling down to mature. When first establishing themselves in an area, Pacific oysters settle on a hard substrate, such as blue mussel shells. Once the oyster population is established, young oysters are perfectly capable of settling on the shells of older oysters. They require about two years to reach a size worth eating. They don’t stop there, living as long as thirty years, during which time they grow to forty centimetres in length and more than a kilogram in mass. In places, they can grow to a density of between 500 and 1,500 individuals per square metre.

  How bad are Pacific oysters in the Wadden Sea? There may not be much of an oyster fishery left in the region, but native blue mussels are still harvested. In places, oysters have overgrown blue mussel beds, creating difficulties for that fishery. Oyster numbers are up and mussel numbers are down, but it has proved difficult to draw a direct line from cause to effect and rule out coincidence. Blue mussel beds are fundamental for biodiversity in the region, providing a home for myriad marine life. It is not yet clear if oyster beds will provide the same foundation. The Pacific oyster is now a dominating species on Wadden Sea tidal mud flats and may, in the future, profoundly alter the ecology of the region.

  France harvests about 150,000 tonnes of Pacific oysters annually. However, this is a fishery based on cultured oysters that are harvested when they are small. Wild Pacific oysters are not attractive to the consumer. They develop in huge clumps, grow so large as to be unpalatable, and come to the table covered with barnacles and other encrusted sea life.

  AMONG THE COUNTLESS PROBLEMS associated with cellular telephones is the fact that I don’t have one. Moreover, when you try to call a cellphone from a payphone, you need to shovel in coins at a furious rate. So when Lisa and I discovered that some feebleminded city planner had put the end of the rail line in Den Helder on the opposite side of town from the ferry that would take us to Texel, we had to call my contact, Norbert Dankers, on his cellphone to tell him about the delay.

  Almost as soon as the call was connected, the payphone started to beep to tell me that my 50 cents had been used up. As Norbert began to give me instructions to the ferry terminal, I dug out a €1 coin, and stuffed it into the hungry slot. “Look for a big town square then BEEP BEEP BEEP.” Another euro. “… Go straight ahead until you see BEEP BEEP BEEP.” By this point, I was out of €1 coins, and the box then proceeded to ignore the parade of other coins I stuck into it, choosing instead to beep at me until I hung up.

  The ferry to Texel was big and zoomy, and decorated in all the latest designer colours. After a twenty-minute ride, we found Norbert waiting for us with a van from the Royal Netherlands Institute for Sea Research. Norbert explained that the ferry was a little more crowded than normal because the region had been visited by its first humpback whale in 300 years, and folks were flocking to the region to see it.

  With a grey beard and wire-rimmed glasses, Norbert is a classic example of a field biologist. Three years from retirement, he had a face that showed the effects of many mornings spent in a bracing wind. However, as a resident of the Land of the Super-fit Citizen, he cycles ten kilometres to and from work every day. Not satisfied with this, he trains once a week with a cycling group to improve his speed. That is before his training to run half-marathons.

  In Norbert’s office at the Institute, we were joined by Rob Dekker and Gerhard Cadée, both with an interest in introduced species and the way that these creatures fit themselves into the local food web. They began filling us in.

  When considering the potential impact of introduced species, they explained, it is important to assess whether or not local species are suffering from the intrusion. The intruder might be finding its own little niche and simply fitting in. Are Pacific oysters messing things up for the local fauna? Mussels are generally between 30 and 40 percent meat, and the rest is shell. In some regions where Pacific oysters have become very abundant, the meat of mussels has fallen to 18 percent.

  Not all the mussel beds in the Wadden Sea have been taken over by oysters. However, as with all such things, it is hard to predict what the eventual outcome might be. In other regions, attempts to remove them have cost €30,000 per hectare. If an effort were made to try to control oysters in the Wadden Sea, we were told, it would probably require ten full-time ships.

  Lisa and I heard that once Pacific oysters have grown to full size, and after they have reached reproductive age, they are very stress-tolerant. They can deal with low salinity, and it takes exposure at low tide at –10°C to kill them. Lisa admired the shell of a particularly crenulated oyster that Norbert said was the result of the chemical tributyltin (TBT), an anti-fouling agent painted on ships’ hulls to discourage barnacles and other nasty hitchhikers. TBT didn’t kill Pacific oysters; it just made their shells more ornate.

  Much of the Netherlands is either created or transformed landscape. Islands like Texel are just about the last bit of unaltered area of their type—naturally created and constantly moving sandbanks. We heard that the North Sea is overfished, but as it’s a marine environment, people cannot directly see the damage and so have trouble imagining the scale of the destruction. In contrast, the coastal portions of the Wadden Sea are exposed at low tide; you can see the area, and so people become involved in its preservation. There is interest in having the Wadden Sea established as a World Heritage Site. The region is
generally thought to play an important ecological and economic role and is recognized as an important nursery for North Sea fishes.

  THE FELLOW WHO CHECKED US in to our hotel in Den Burg was the very model of a company man. As he waved his shaven head at us hypnotically, he explained that the hotel restaurant was a fine place to dine. “It can be put on your bill!” We said that we would probably find something to eat in town. He went on to extol the virtues of the hotel’s bar, explaining that the tab could be put on the bill. “Well, that sounds nice,” we said, even though it didn’t. We asked about our options for renting bicycles. “I can make a reservation for you and put it on your bill.” Lisa asked for alternatives. He responded: “Rent a bicycle or rent a car.” We allowed him to make the bicycle reservation and put it on our bill.

  “I am sure that you will want this guidebook. It has everything you will want to know about Texel. It has maps.”

  “I have good maps.”

  “It has a tide table for Texel.”

  “I downloaded a tide table for Texel.”

  “It has everything,” he claimed. Lisa asked if he had an English version.

  “No, just Dutch and German.”

  “But we don’t read Dutch or German.”

  “I can put it on your bill.” After that much sales effort, I let him put it on our bill. If Lisa hadn’t been with me, I suspect he would have offered to find me a prostitute and put her on my bill.

  In the town’s main square, we found a nice little restaurant that served pancakes and the products of the Texel bierbrouwerij. On offer was Texels Amber and Texels Goud, but I settled on a Texels Witbier. It was close enough to vile as to be quite refreshing. Lisa pointed out that the restaurant’s music system played nothing but mid-’70s one-hit wonders. We watched the parade of cyclists, from pre-schoolers through advanced seniors, with not a helmet in sight. As a young boy, I probably would have donned a wig and called myself “Brenda” before I would have put my leg over a girls’ bike, the type with no cross-bar. On Texel, there was no obvious “thing” about a man riding a girls’ bike.

  THE DAWN PROVIDED BEAUTIFUL SUNNY SKIES and no wind. Slathered in SPF 20 sunblock, Lisa and I set off for the bicycle rental shop. This was pretty brave of me. The last time Lisa had got on a bicycle, about fifteen years earlier, she had swerved out of control and run me down. Growing up in rural Alberta, surrounded by gravel roads, Lisa had never come to terms with pedal power. But, she explained, she would have felt foolish trying to get around Texel any other way. It was going to be transportation the way the locals did it or nothing at all. She had been worried about having no control and swerving into the path of oncoming Dutch seniors. But once she got over trying to grip the handlebars too hard, she developed a mastery of her two-wheeled beast and was left with a sense of personal accomplishment. “I even managed to signal twice without going out of control.” She used the expression “KaPEEba” to indicate what the crash would have sounded like, and I resisted the temptation to ask what part of the collision would have made that sound.

  We set out from Den Burg along scenic and perfectly flat bicycle paths, past Oosterend, along a nasty detour for road construction near Oost, and on to the Lancasterdijk that separates the low-lying parts of the island from the Wadden Sea. The dyke was given its name in commemoration of the crew of an Allied Lancaster bomber that crashed there in WWII.

  We reached the sea about an hour before low tide would expose the oysters, and so watched shorebirds foraging on sea life left behind by the receding waters. Adjacent fields were filled with lapwings, spoonbills, and avocets. We also watched a rich cross-section of the island’s residents and visitors cycle by. Many of these cyclists were considerably older than us, and were probably pedalling further. If I were to move to Texel, I suppose I would have to begin a diet of muesli and mega-vitamins just to keep up.

  Lisa and I leaned back on the Lancaster dyke, soaking up the sun, eating almond pastries and waiting for the sea to recede. We didn’t really know what a Pacific oyster bed might look like from the shore, but big black smudges were being revealed at the water’s edge some hundreds of metres away. We walked across the tidal flat, trying to choose a route to the biggest smudge that would be least disturbing to the birds foraging on what the outgoing tide had left behind.

  As we proceeded, the smudges revealed themselves as patches of oysters. Shoal beds, they stretched a couple of hundred metres. Ugly little devils. Rob had told us that they are unappealing to eat because they are too big to swallow in one gulp. They were grey, corrugated, rock hard, and cemented to everything else in sight. In turn, everything else was cemented to them, including barnacles, snails, and red and brown algae.

  You have to give Pacific oysters in the Wadden Sea a high score on the yuck scale even before getting to the squishy bit on the inside. They would probably be best described as beautiful when covered at high tide. Lisa claimed to be surprised that there weren’t more of them, given the big hype. Nasty-Pacific-oysters-as-far-as-the-eye-can-see sort of thing. But it was clear that if they continued to spread, occupying more and more of the intertidal zone, Pacific oysters would become an ecological force to be reckoned with.

  We played in the sea for about an hour, collecting particularly nice examples of each shell type we saw, after ensuring that their owners and everything attached to them had died. On that day, it seemed that being a biologist was an excuse to splish-splash in the water, get muddy, pick up dead stuff, and get paid for doing it. It was an excuse to be a four-year-old child without an authority figure hovering over you. Standing in any one spot too long was ill-advised, as black organic ooze crept up from under the clean tan-coloured sand and engulfed our feet, making the whole experience that bit more delightfully gross.

  We cycled south along the coast to a second spot that Norbert had recommended and watched as the sea retreated further from land. As it did, it exposed more indistinct black smudges, but much further out. I contemplated whether I had seen enough oysters for one day or whether I should tromp out to this next group. One ugly oyster is pretty much like another, right? But my conscience got the better of me. First, I had come a very long way to see Pacific oysters, and surely more was better than less. Second, I knew that Norbert would ask me whether I had visited both sites. And so, with Lisa reclining on the dyke, I set off across the sands.

  Or rather, I set off across sands covered everywhere by five centimetres of sea. No matter what my route, each step submerged my sandals and toes, but not my ankles. There seemed to be no way to get around flocks of birds taking advantage of the low-tide bounty. There were lots of gulls, plenty of raucous oystercatchers, with a handful each of turnstones, ducks, and geese, accompanied by endless shorebirds that even the most devout birdwatcher doesn’t try to identify.

  Patches of oysters became larger and more common as I got further from shore. I stepped over and around beautiful patches of red, brown, and green algae, and avoided stranded jellyfishes, knowing that their dying remains can still sting. I marvelled at tiny transparent comb jellies and strained to see minuscule transparent shrimp that could be found most easily by spotting their shadows.

  And after more than twenty minutes of walking, I got to a really substantial oyster bed. It was as ugly as the biggest one at the first site, but without the fetid black ooze underfoot. But I found that I couldn’t stop there. Like a magpie drawn to a broken metal watch-strap, I walked further and further out, following oyster beds that turned into oyster reefs, reaching upward from the sand. In spots, cormorants roosted on the oysters, drying their wings in a crucifix posture.

  Then I remembered that along parts of Canada’s east coast the tide comes in faster than a person can walk. I checked my watch and then the tide table in my pocket. The tide was returning, and I was more than a kilometre from shore. Checking the tide table again, I found that, where I was standing, the sea would reach almost exactly the crown of my head. No real need to worry though, as I had only a thirty-minute walk to shor
e and the tide would require six hours.

  It had taken several decades, but I really felt that I was getting the hang of working for a living. Like everyone else, I had survived plenty of jobs that were less than entirely appealing and barely paid the bills. I had washed trucks, filled oxygen cylinders, unloaded empty beer bottles from trucks, and scraped bakery floors. But on this day my life as a biologist was transcendent. As the sea slowly recovered its oysters, Lisa and I watched the sun shining off clouds to the east, making a stunning reflection in the wet sand. Lisa was in such a good mood that she indicated that she would be willing to eat an oyster if it would help my narrative. I explained that it wasn’t part of her job description.

  CHAPTER THREE

  The Attack of the Killer Rhododendrons

  REASON NUMBER THREE FOR INTRODUCING A FOREIGN SPECIES: BECAUSE I NEED TO REPLACE THE TREES I CUT DOWN.

  WHEN IT COMES TO BIG, BOLD, AND BEAUTIFUL FLOWERS, it is hard to beat a rhododendron. You also have to give them big points for variety; there is something like 1,000 recognized species, supplemented by all manner of hybrids. Colourful and showy to a fault, they have a wealth of admirers. In Victorian Britain, there was no shortage of adventurers willing to travel to eastern Asia and risk their hides in order to collect new species of rhododendron and bring them back to England. This troupe included such luminary botanists as Joseph Hooker, who brought back about thirty species, and the aptly named George Forrest, who hauled home an astonishing 300 species. Today, rhododendron fanciers’ clubs are found everywhere the plant can be cultivated. Rhododendrons have even been named the state flowers of Washington (Rhododendron macrophyllum) and West Virginia (Rhododendron maximum).