Parallel but different universes on each side of the Tasman.
Feathers to fur is a moniker that evokes images of the fashion industry and the chic elite, however it was also the title of the 2007 New Zealand Ecological Society conference, held recently in Christchurch. The meeting is a forum where more than 200 ecologists from around the country share research findings, set up collaborations on new projects and debate current issues in ecology. This year the main symposium discussed the ecological transformation of Aotearoa, from bird-dominated ecosystems to those subjugated by invasive exotic mammals and characterised by habitat loss. The conference was in part an update of research presented at an earlier symposium, entitled “Moas, mammals and climate.” The papers from the original conference are available from “http://www.nzes.org. nz” http://www.newzealandecology. org, see issue 12(s). Papers from this month’s conference will be released within 18 months. The symposium opened with a discussion of insects—not what you might expect given the vertebrate focus of its title. However, the transformation from avian-dominated ecosystems to a mammalian empire has had profound impacts on all our biota, even the smallest animals. Insect-eating birds relied on visual cues and movement to detect their prey, whereas mammalian predators hunt using odours and are active both day and night—when most birds are sleeping. Hence the defence mechanisms and ecological traits that evolved in the New Zealand insect fauna to survive bird predation—such as cryptic colouration, freeze responses and a nocturnal lifestyle—are useless against the new foes. Examples of localised extinctions, such as giant weta from rat-infested mainland New Zealand, were given as a case in point. The change in predation regime is at the heart of the demise of our insects, birds (aptly described as a wreckage of an avifauna with 58 species, 24 per cent of the total, now extinct), changes in the composition, pollination and seed dispersal of plant communities, and the new predators even affect the abundance of native fish. See was discussed against a background of three periods in the history of New Zealand herbivory. In the first, pre-human era, herbivory was dominated by birds, such as the moa, whose droppings (coprolites) show evidence of feeding on at least 64 plant species. Second was a period between the demise of the large herbivorous birds and the arrival of introduced browsers, and the third period has been dominated by introduced mammalian browsers. As an aside, a brilliant summary of available data that included the dating of early archaeological remains, sub-fossil kiore bones, rat-gnawed seeds, pollen records and charcoal deposits provided the most comprehensive and conclusive evidence yet of a late arrival of Polynesians to Aotearoa, dated at approximately 1280 AD. As such, the second period in which large herbivores were absent, lasted for at least 400 years. Two issues concerning plant-herbivore relations were debated during the symposium: first, are the unusual plant adaptations in New Zealand the result of an avian-dominated plant-herbivore system or an adaptation to oceanic climates, and second, are deer the equivalent of moa? The key plant adaptation promoted as a means to resist bird browsing is their filiramulate form (defined as slender, wiry twigs, which may be divaricate, zigzagging, or flexuous) particularly in their juvenile stages. Cafeteria-style studies where emu (close relatives of moa) were presented with a variety of food plants showed that the filiramulate form inhibited the birds’ ability to forage for food compared to larger broadleaved plant species. However, birds are not the only influence on our vegetation as climate can play a significant role. New Zealand’s largely oceanic climate makes it highly suitable to coniferous species such as rimu, kahikatea, miro and matai. The regeneration patterns of many conifers are linked to extreme disturbance events such as floods, volcanic eruptions, windstorms and earthquakes. In fact, regeneration patterns observed by determining the ages of trees throughout Westland clearly show the impact of significant alpine fault movements dated at 1450, 1620 and most recently in 1717. Deer were rejected as a surrogate for moa browsing, despite the fact that they inhabit the same regions as the now-extinct moa and operate at the same trophic level. Deer during the 1950s were at least 100 times more abundant than moa ever were and they remain 10 to 20 times as numerous, the drop due to extensive aerial hunting. Mammalian herbivore pressure is therefore much higher, and likely also uses different selection criteria for palatability, significantly altering the grazing regime. A second and historically overlooked factor is the trampling effect of deer. The foot print of a deer is twice as heavy on the forest floor as that of a moa, due largely to the small size of its feet. This increased point pressure in combination with the greater abundance of deer is a possible explanation for the reduced soil invertebrate fauna where deer are present in high numbers. I would like to highlight something described at the symposium as an ecological scandal. It has nothing to do with feathers or fur, but everything to do with fish scales and the introduction of salmonid fish, better known as trout. Reports of historical whitebait catches of up to 300 kg from the Hokitika River were discussed, something one can only dream of today. The decline of these migratory fish populations is thought to be the result of barriers (such as dams) to the dispersal of diadromous fish (those with an oceanic phase to their life-cycle) and degradation of habitat in breeding grounds by extensive land clearance. However, for our non-migratory native fish, the principal limiting factor appears to be the presence of trout. Even relatively small trout 15 cm long are capable of eating the entire suite of non-migratory native fish, and in many cases there is little cohabitation of native species and trout. A challenge was issued that perhaps the time has come to look seriously at removing trout from some streams. Diversity equals stability—sound advice you are likely to hear from your local financial adviser and maybe your forest ecologist. A diversity/stability debate has raged in the literature for the past decade. Some ecologists believe that a healthy ecosystem requires a diverse array of species to function properly and that the current unprecedented loss of biodiversity could have dire and unpredictable consequences. Analogies have been drawn with an aeroplane that keeps losing a bolt here, or a species there. It will function up to a point, but eventually a catastrophic system failure will result in the demise of the plane/ecosystem. Adding to this global debate, Eckehard Brockerhoff of the Crown Research Institute, Scion, has shown in a review of 119 international studies (see Ecology Letters, 10 (9): 835–848) that increased diversity of tree species (producers) significantly reduces herbivory by insects (consumers),. The impact of oligophagous insects (those that have a narrow host range) was almost always reduced in diverse forests compared to mono- cultures, however the response of polyphagous insects (those with a wide host range) was variable. In addition, it appears that tree species composition is more important than straight diversity. Studies of mixed forests showed that a combination of taxonomically diverse species were subject to less herbivory than groups of closely related species. So what are the implications of this research to our forests? New Zealand’s beech forests are dominated by a handful of closely related species from the genus Nothofagus. Natural monocultures (or bicultures), beech forests occasionally suffer significant outbreaks of several herbivores, including scale insects, beech buprestids and pinhole borers. The causes of beech forest die back have been intensely debated, as it may be brought on by abiotic pressures, such as drought stress. Nonetheless, the study suggests that the large areas of our native forests—and our plantation forests—dominated by a handful of species are potentially vulnerable to herbivorous insects, either indigenous or introduced. To end on something completely different: how does your garden grow? Angela Moles, a lecturer in plant ecology at Victoria University, has taken a global perspective on this age-old question. She and colleagues from Australia have been researching the twining behaviour of plants, and have recently published their findings in Global Biogeography and Ecology, 16: 795–800. No one has taken a systematic approach to answer the simplest question; in what direction do plants twine? Anecdotal reports suggested that plants tended to form helices that grew in an anticlockwise direction. However, was this a local phenomena or something wider? In a study of 17 sites in nine countries that spanned both hemispheres, Angela found that 92 per cent of all plants coiled anticlockwise. The global synchrony of this phenomena means that traditional explanations such as the Coriolis force (that supposedly determines which way the water flows from your sink) or the celestial path of the sun cannot explain this almost unidirectional twining behaviour. In animals such directional asymmetries have been ascribed to the orientation and operation of microtubules. Microtubules are small subcellular structures that are part of the cytoskeleton, or structure of cells, and modulate many cellular processes. Further research is required to test this hypothesis, however it aptly shows that even the simplest observation can open a Pandora’s box of complex biological questions.
Herceptin is a drug that has attracted a fair measure of attention and controversy in recent years. It is used in the treatment of a certain type of breast cancer where some deem it to be of considerable benefit. Unfortunately, it is also very expensive and has adverse effects on the hearts of some patients. While we will consider some of these points later, the drug itself merits attention. Far from your everyday pill, it is termed a “humanised monoclonal antibody” and is one of the first such compounds to enter clinical use. Monoclonal antibodies were a Nobel Prize-winning invention of the late 1970s. To appreciate their ingenuity you need to understand some immunology.
Amidst all the talk of climate change, there is one important consideration I’ve seen no mention of. We know that the poles are warming more than most places, and the northern polar regions have so far been harder hit than Antarctica. For the first time in living memory, the North West Passage around the top of Canada and Alaska looks to be clearing its throat. Shippers—especially Americans—are thoughtfully scratching their chins and checking the ice damage clauses in their insurance polices. Canadians are setting up a new far-northern naval-cumcoast-guard base, reminding the world—especially that part of it close to their southern border—that this possible route lies well within their territorial waters and there’s not going to be a mass-migration of supertankers through their their back door any time soon. Environmentalists are tearing their hair, warning of the ecological fragility of the Arctic, the imperative of keeping ships and their toxic oil far away. Meanwhile the Danes in Greenland and the Norwegians and Russians further east are posturing and honing their cases to the UN in the hope of extending their territorial waters on the basis of undersea geology as we ourselves are doing nearer at hand. Ironically, they hope for large oil deposits under the Arctic Ocean. We know the polar bears are in trouble. They give birth in winter/spring and depend on being able to fatten up on seals to feed their growing cubs. As long as there is plenty of ice, the bears catch the seals when they come up through holes in the ice to breathe. As ice melts earlier in spring/summer, the seals get into open water earlier where the bears can’t match their swimming ability and in consequence, the polar bears starve. But polar bears aren’t the only large mammals to be found ashore in the Arctic. There’s Santa and the reindeer, completely overlooked in every summation of the consequences of polar warming. Every child knows that Santa lives at the North Pole and those reindeer can’t be far away. Yet in a just a few decades, cognoscenti are predicting a distinct shortage of ice at the North Pole in summer—in fact none. Polar bears may not be a match for seals in the water but they can swim pretty well. However, Santa and the reindeer? Santa was mature when I was a kid so he’s no spring chicken, and although he has a layer of insulating adipose tissue, I can’t see him treading water for long. His regulation uniform wouldn’t be especially buoyant and there is no hint of wet or dry suits in his rather limited wardrobe. Then there’s the presents. Seawater doesn’t affect plastic too badly (see our news piece on p14 of this issue) but there are probably still a few metal components that are bound to rust. Turning the pages on wet books certainly slows down the reading experience, and sodden clothes and books are significantly heavier for the reindeer to distribute. That extra weight could mean that Santa has to buy additional carbon credits because he and the reindeer will be burning a whole lot more energy as they flit through the sky and manoeuvre sacks of presents down increasingly tight ecofriendly chimneys. Keeping track of who wants and gets what, and then assembling the goods in a timely and orderly fashion has always struck me as pretty daunting—possibly even more arduous than acquiring all the components for an issue of New Zealand Geographic. It’s a challenge that Santa has seemingly always risen to. But once everything starts sloshing around in the waves, it’s certainly not going to get any easier. What could be done to help? Of course, there are always those tiresome suggestions about switching to smaller cars that burn less fuel, using public transport more, getting farm animals to fart less etc etc. In fact, in a new book (Carbon Neutral by 2020: how New Zealanders can tackle climate change, edited by Niki Harré and Quentin Atkinson and published by Craig Potton Publishing), some authors go so far as to claim that we shouldn’t even be re-modelling our kitchens and bathrooms every five years with water-soluble MDF! Use pine and the cabinets will last for 50 years is just one of myriad repugnant ideas it contains. I doubt that we’ll do sufficient to save the North Pole from summer melting. Santa could become a seasonal worker, but he’d likely have insufficient preparation time each year with the world’s population still growing steadily. However, New Zealand could help him. We could seize the global initiative and offer him a safer home in our sector of Antarctica. Unlike the situation at the North Pole, much of Antarctica is undergirded by land and it’s unlikely to disappear anytime soon. Speaking of disappearing soon, this is the last issue of New Zealand Geographic I am editing. Being almost as old as Santa, I’ve decided to quit while I’m still alive and try to do a bit of hiking around the hills—something I’ve not done in many years. I’d like to thank Mark Bathurst for his indefatigable attempts to improve my prose and that of others, the many willing contributors without whose efforts there would be no magazine, the patient and supportive people at Rural News, and particularly my magnificent art director Andrew Caldwell. We’ve worked side by side for 10 years with remarkable harmony and I’ll miss his eccentric music, quirky humour and lively intelligence. James Frankham, who contributed an article on refugee taxi drivers in Auckland in issue 74, is the new editor. He has written books, is a competent photographer and also works as a documentary film-maker so brings a wealth of talent and insight to the editorial desk. And I thank you, the patient readers, without whom all our efforts would be pointless.
Between the Bay of Plenty, the Urewearas and the central North Island lies Murupara, a town that lives and dies by timber. To the east rises the steep face of the beech-clad Ikawhenua Range, to the north, west and south, hundreds of thousands of hectares of pine plantations. Here a stacker, which can grab 40 tonnes of logs at a time, loads rail wagons in the Murupara log yard.
Severe gale westerlies gusting 130 km/h tore into Invercargill around dawn on Tuesday October 23, felling trees and chimneys, ripping off roofing iron and smashing in windows. Sheds, hothouses, verandas and a bus-stop were blown away and the brick wall of a building in Bluff collapsed as most of the roof came off. A fireman needed stitches after he was blown off a roof in Bluff and a number of people were treated for injuries caused by flying debris. Because the winds came early, many people stayed inside and several schools cancelled lessons for the day. However, staying inside did not guarantee safety. One woman was eating breakfast in a farmhouse when part of the ceiling hit her in the face after a tree fell on the house driving a large branch through the roof. Fallen trees blocked roads and railway lines as well as cutting power to 2500 homes. Otago was affected as well, with downed lines cutting power to 5000 homes. A couple of trucks were overturned on Windy Ridge near Balclutha, where a hole was punched in the roof of the swimming pool. Near Oamaru a fire started when trees came down over power lines. The South Island did not have a monopoly on destructive wind. Later in the day, in central Hawke’s Bay, five trucks were blown over on the Takapau plains between Dannevirke and Waipukerau. An ambulance was also blown off the road and then rolled through 360°, ending up back on its wheels. The driver was shaken but unhurt and a second ambulance was dispatched to rescue a woman trapped in her car by a fallen tree. The damaging winds were caused by an intense depression passing just south of Stewart Island. This depression deepened by 33hPa in 24 hours as it moved rapidly east from near Tasmania. To meteorologists, such rapid deepening is known as “explosive cyclogenesis” and the resulting deep low colloquially referred to as a “bomb”. Bombs occur with devastating effect off the east coast of the United States where rapid deepening in excess of 40hPa has been recorded. In the Southern Hemisphere, the western Tasman Sea is one of the most favoured places for explosive cyclogenesis. A number of circumstances have to coincide for explosive cyclogenesis to occur. A warm ocean current running adjacent to a cold landmass or body of cold water is one. As a consequence of the earth’s rotation, warm ocean currents, moving water from the tropics towards the poles, are found east of all the continents. In the North Atlantic, the Gulf Stream runs up the eastern seaboard of the United States, while in the western Tasman Sea, a warm current heads down the Australian east coast, then near Tasmania, meets colder water coming from the west. The sea surface temperature affects the temperature of the air above it, so where warm water runs adjacent to cold water, you find warm air meeting cold air, which promotes the formation of fronts and lows. Another ingredient in the recipe for a bomb is a fast-moving shortwave trough in the middle atmosphere. In the pressure contour lines of a mid-level weather chart, this shows up as an upside down U shape. As the trough moves rapidly eastwards, the air moves even faster through the trough. Air passing through the sharply curved apex of the trough gains cyclonic vorticity which it carries downstream and this causes air pressure to fall at sea-level. The faster the mid-level winds and the sharper the curve round the trough, the greater the effect in lowering surface pressure. Similarly, a favourable orientation and acceleration of the jet-stream in the upper atmosphere can further enhance the lowering of surface pressure by removing air from above the developing low faster than it brings more air in from upstream. Finally, a key ingredient in explosive cyclogenesis is a plentiful supply of low-level air with high moisture content. As this air rises inside the developing low some of its water vapour condenses to liquid thereby releasing into the air the considerable amount of energy needed to evaporate the water from the sea-surface in the first place. The heat makes the air expand, which further lowers atmospheric pressure at the surface. All these conditions were met in the formation of the bomb on October 23, but the contribution from the vorticity in the strong westerlies stood out as particularly significant. October turned out to be a particularly windy month over the New Zealand region. Statistics keep by NIWA showed that it was the fourth equal windiest October on record! When the atmospheric pressures were averaged for the entire month and compared to the long-term average, pressures along 50° south from below Tasmania and New Zealand were found to be 7 to 10 hPa below average, while pressures from about Auckland northwards were higher than average. The strength of the westerlies depends on the temperature difference between the tropics and the Antarctic. Interestingly, during October this year the sea-ice extended further away from Antarctica in the longitudes of Tasmania and New Zealand than normal. Sea-ice forms around Antarctica in autumn and winter reaching a maximum of 19 million sq km in September, and then rapidly diminishes to a minimum of 3.5 million sq km in February. Air moving off the Antarctic towards New Zealand can receive as much as a hundred times more heat from the ocean surface as from sea-ice. Even though the surface water temperature near the ice edge is around 0° C, it is significantly warmer then the ice surface and so can transfer more heat into the air flowing off the frozen continent, whose temperature can be as low as minus 20° C. Furthermore, sea water evaporates readily into the dry Antarctic air, particularly as breaking waves throw up tiny droplets of spray. As it is heated from below, the air rises and shower clouds form. When clouds form, water vapour condenses, thereby releasing further heat into the air. So, when the sea-ice extends further towards New Zealand than normal it has the effect of concentrating the pole to equator temperature difference over a smaller range of latitudes and therefore intensifying the westerly winds in our region. Paradoxically, the stronger westerlies then act to erode the edge of the sea-ice, which is mostly less than a metre thick, and therefore easily broken off by the heavy swells created by the westerly gales. In the atmosphere, feedbacks occur across a wide range of processes. Just as the particularly strong westerlies of October were an important ingredient in the explosive formation of the bomb that brought destructive winds to Invercargill, so the strong westerlies contained the seed of their own destruction by whipping up heavy swells to chew off the edge of the sea-ice.
A tribute to some of the most detested birds in the world from a biologist who studied them in the field for 40 years and came to appreciate their many admirable qualities.
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