Kaikoura to Greymouth—the hard way. That's the guts of the South Island Four-Wheel-Drive Coast to Coast Teams Enduro, now in its sixth bone-jarring year. New Zealand Geographic sent two masters of the mudhole, wizards of the winch, lone rangers of low ratios along for the ride.
This winter, the Department of Conservation is attempting to eradicate kiore, the Pacific rat, from the important wildlife sanctuary of Codfish Island. The project is the latest in a drive to increase the number of "safe" islands where some of the world's rarest bird species can continue the long trek back from the edge of extinction. Lying two kilometres west of Stewart Island, Codfish is only a dot on the map less than 1400 hectares but it will be he largest southern island to be cleared of rats. Early Ngati Mamoe and Ngai Tahu probably introduced kiore to the island they called Whenua Hou as a food source, to supplement the titi (mutton birds) their descendants still harvest annually. Like the European colonists who followed, releasing goats, pigs and rabbits on many islands, they had no concept of the devastating effect the liberation would have. The three species of rat found in New Zealand are all significant predators of the country's native birds, which have evolved free from terrestrial predators. The largest, the Norwegian rat, is the most destructive, taking eggs, chicks and adult birds. The ship, or black, rat climbs more readily than the others, and often destroys nests after eating their occupants. The kiore is the smallest, but it, too, eats eggs, chicks and even adult birds much larger than itself. It is not just their taste for meat, however, that makes rats a danger. By clearing the forest floor of seeds and seedlings, and thus preventing the establishment of new generations of plants and shrubs, they have modified the habitats of many bird species. Furthermore, they compete directly with birds for essential seed, insect and plant food to such an extent that some birds, and the plants they rely on, have disappeared from many mainland areas. Preparations for the mass extermination to be carried out by aerial application of cereal bait laced with an anticoagulant toxin have been under way for over three years. Project manager Pete McClelland says organising the poison drop is the easy part: "The difficulty is knowing how to protect our endangered species from the poison, as each must be treated differently." First to be taken care of was the island's 60-strong fernbird population. Last year, 20 of the secretive birds were transferred to nearby Putauhinu Island, and subsequently nested during spring. McClelland describes the Putauhinu population as an "insurance policy," a safeguard against the unlikely event of deaths among the birds left on Codfish Island. As an added protection, the main fernbird habitat on Codfish, an area of about 40 hectares on the eastern side of the island, is to be left untouched by the poison drop. Instead, bird-proof bait stations will be placed throughout the area. Trials have shown these pose no threat to the birds, but using them over the whole island is not practical. Next to be looked after were Codfish Island's 45 kakapo. Earlier this year, the entire population was located with the help of trained dogs and moved to another offshore island, where the birds will reside until the baits have decomposed and are no longer a potential danger. A third species requiring protection is the tiny short-tailed bat, there being an outside chance that a few of these insect-eating mammals might consume an insect that has fed on the baits. To find out where the bats roost, a number will be trapped in mist nets and fitted with minute radio transmitters, allowing their movements to be traced. Shortly before the poison drop, harp traps will be set near the roosts to catch the bats as they fly out for their evening feed. The captives will be kept in specially constructed "bateries" until the operation has been completed. "These are the difficult tasks," says Pete McClelland, "and because we are dealing with rare species, the people we are employing are specialists. We also have to time the poison drop to coincide with the time of least available natural food for the rats. A little too soon, and they could ignore the bait in favour of their usual food. A little too late, and some of the females may be in their breeding burrows and miss the poison on the two or three days it is effective." Complete eradication of rats from island sanctuaries is a long-term mission which is being executed with all the precision of a military campaign. Ulva Island, in Stewart Island's Paterson Inlet, has already been declared rat-free, and nearby Putauhinu and Raratoka are expected to be rat-free next year. Kapiti Island, off the south-west coast of the North Island, was cleared two years ago. The programme has attracted support from Ngai Tahu, who have become concerned at the loss of native birds from southern offshore islands. Some of the families who visit Codfish Island each year to harvest tin have asked for DoC assistance to clear other islands of rats.Andy Cox of DoC's southern conservancy says that 15 years ago the task of rat eradication, even on the smallest island, was thought impossible. At that time he was employed by the Wildlife Service of the Department of Internal Affairs, with special responsibility for the recovery of endangered species. "We knew how to get rid of deer and possums from the islands we wanted to use for rescue operations," he says, "but rats were con-sidered an unbeatable pest." Now he looks forward to the time when islands much larger that Codfish, such as 11,300 ha Campbell Island in the subantarctic, can be tackled with confidence: "Each of the islands in the programme is a building block that we add to our knowledge base." But time, he emphasises, is of the essence: "If we move too fast, we run the risk of overreaching ourselves, and of failure. But if we move too slowly, we draw out the time our endangered species are under threat." The time for Codfish, however, is now.
A unique breed of cattle from Enderby Island, in the subantarctic Auckland Island group, has been saved from extinction by a combination of luck and high technology. Using the latest artificial breeding techniques, AgResearch scientists at Ruakura have produced a pure-bred calf from the last remaining Enderby Island cow, an elderly matriarch known as Lady. Lady survived against all odds on Enderby, evading one intensive cull and several subsequent attempts to rid the island of unwanted mammals. The saga of the Enderby cattle began in 1895, when nine cattle and 20 sheep were landed on the 688 ha island to form the basis of a mixed farming operation. These cattle were either of shorthorn or Shetland stock it is difficult to decipher the original bill of lading. The futility of trying to farm in the Auckland Islands described as having "the most miserable climate on earth" soon became apparent, and the venture effectively ceased in 1910. A few remnant stock were left behind to fend for themselves in the dismal conditions. The sheep died out, but, surprisingly, the cattle survived in part because of their habit of foraging for seaweed when inclement weather precluded grazing on the megaherbs or tussock that form the natural vegetation of the island. However, in tandem with rabbits (which had been introduced in 1865 to provide sustenance for shipwreck victims), the cattle put increasing pressure on the native flora and fauna of the island. The native South Georgian diving petrel became extinct on Enderby, and populations of the New Zealand sea lion and yellow-eyed penguin were adversely affected by the newcomers. Under its mandate to protect the natural biota and environment, the Department of Conservation began to consider eradicating both cattle and rabbits. But as pressure to restore Enderby to its original condition mounted, so did awareness of the need to preserve the uniquely hardy Enderby cattle. With restoration of the island and in situ preservation of cattle incompatible, the Rare Breeds Conservation Society suggested establishing a breeding population of Enderby cattle on mainland New Zealand. The logistics and costs of getting live cattle off Enderby seemed insurmountable, so it was decided to concentrate on retrieving eggs and sperm during the cattle culling operation: mature cows were to be autopsied to remove eggs, mature bulls to have sperm collected post mortem. The extermination operation on Enderby went ahead in 1991. Hunters shot around 50 cattle during the three-week operation. The genetic heritage of the breed was assumed to be safe in the eggs and sperm that had been harvested and frozen. However, upon examination in New Zealand, none of the eggs proved to be viable, and much of the sperm was of poor quality. On the assumption that no cattle had survived the cull on Enderby, the RBCS began a breeding programme using in vitro fertilisation of non-Enderby cows with Enderby sperm. After extensive efforts, seven half-bred cattle were born, all of which were bulls. This was not a useful outcome. Mating these bulls with other cattle could only dilute the Enderby genetic identity still further, with resultant offspring being just one quarter Enderby Meanwhile, DoC learned to its surprise that a handful of cattle were still alive on the island, and continued its efforts to shoot them as opportunity presented, apparently unaware of the difficulties that the RBCS was having. By the time the RBCS learned of the survival of some cattle, only a single cow and her calf remained. Logistical difficulties notwithstanding, the society decided it was imperative that these cattle be physically removed alive from the island, and lobbied hard to gain permission to do so. DoC was about to start poisoning the Enderby rabbit population, and agreed to allow the RBCS to use the facilities associated with that campaign to capture the remaining cattle and transport them to New Zealand. Unfortunately, the calf did not survive the trip, so hope for the survival of Enderby Island cattle became focused on one individual, a cow which was named Lady. Although Lady by name, she proved to be something of an Old Maid. Traditional artificial insemination (AI) techniques failed dismally. Embryo transfer was then tried. Hormones were administered to encourage the shedding of multiple eggs, followed by AI. The embryos were then flushed from Lady's uterus and implanted into recipient cows, but none survived. Despite these setbacks, Lady did maintain that most critical of female characteristics: continuing a normal cycle of egg release. There was still hope. Aware of the difficulties being experienced in getting Lady to conceive, and acutely conscious that time was running out, the RBCS obtained funding from the Lottery Grants Board to enable AgResearch at Ruakura to become involved. Located on the outskirts of Hamilton, AgResearch Ruakura possesses some of the best technical know-how in advanced bovine reproductive technology in the world. Repeating procedures attempted earlier, Ruakura had the same disappointing results. About all that was left, short of cloning, was to attempt IVF, in vitro fertilisation. In this process, eggs are directly removed from an ovary. Despite the huge number of eggs some 100,000 present in a cow's ovary, only 15 can be expected to be sufficiently mature for harvesting at any one time, and harvesting can only be performed every three days. In keeping with the luck that had dogged the Enderby saga, no more than five mature eggs at a time could ever be harvested from Lady. The IVF procedure involves eggs and sperm being mixed and left for 24 hours in special IVF media. Successful fertilisation is detected by division of the egg cell. A week later the tiny embryo, now beginning to form a foetus and placenta, is placed in an unrelated recipient cow which has had its breeding cycle synchronised with that of the subject. Typically, for every 100 eggs harvested, 30 embryos are produced, 12 of which result in live calves from recipient cows. With Lady, 60 egg collections were made. Despite excellent fertilisation rates using Enderby Island sperm, only 18 embryos suitable for introduction into recipient cows were produced, since most of the embryos died at the four- or eight-cell stage. Only two embryos developed successfully. One of these aborted at 40 days, and the other resulted in a healthy hull calf born in May of this year. This bull calf, and hopefully future brothers and sisters, should ensure the survival of the Enderby breed. Any unique qualities inherent in the cattle beyond a certain perversity in breeding are as yet unknown, and it may be years before they are fully appreciated. But like Old Blue, the Chatham Islands black robin, Lady has probably saved her race.
Mass coral bleaching on Australia's Great Barrier Reef earlier this year is a warning sign of significant climate change, according to the Great Barrier Reef Marine Park Authority (GBRMPA). The authority says this year's bleaching event "would appear to be the most severe and extensive ever recorded." Elevated sea temperature—even as little as 0.5 to 1°C—is believed to be the major cause of coral bleaching, which results when corals expel the tiny algae (called zooxanthellae) which live in association with them Without these symbiotic algae, which give corals most of their colour as well as their food, coral cannot grow and often die. Ray Berklemans of GBRMPA says: "Although other factors such as high light intensity, increased levels of ultraviolet radiation and lowered salinity have also been implicated in coral bleaching, their effect in stressing corals is greatly exacerbated near coral's upper thermal limits." Some corals recover from bleaching through recolonisation and multiplication of their few remaining algae, but heavy bleaching on coral reefs often leads to the death of 20 to 50 per cent of the corals. Recent surveys by GBRMPA show extensive bleaching along 1000 km of the reef. These surveys indicate that 88 per cent of inshore reefs are bleached to some extent, and about 25 per cent are severely bleached (where more than 60 per cent of corals are affected). Dr Peter Harrison of Southern Cross University surveyed corals at Orpheus Island in the Palm Islands group near Townsville, and found 80 per cent mortality of corals. Even massive coral colonies over 80 years old had clied from bleaching. In the northern part of the affected area, discharge of large volumes of dirty water from rivers after heavy floods probably added to high temperatures to cause bleaching of inshore reefs. In the southern part of the Great Barrier Reef, bleaching has more likely been associated with ocean surface temperatures three to four degrees above normal over a huge area of the Tasman Sea, as shown by satellite sea surface temperature (see page 17). Mass coral bleaching events are a relatively new phenomenon, but have been increasing globally since the early 1980s. Past coral bleaching events on the Great Barrier Reef were recorded in 1980, 1982, 1987, 1992 and 1994, and have generally been associated with heatwaves, but the 1998 event is the biggest so far. Extensive coral bleaching has also occurred this year at Lord Howe Island in the Tasman Sea, which possesses the world's southernmost coral reefs. Evidence is mounting to refute sceptics who consider recent global temperature hikes to be part of a normal and natural cycle. Thirteen of the warmest years this century have occurred since 1980, and 1997 was the hottest year on record. This year is shaping up to be even hotter.American scientists say that already the global average temperature is 0.6°C above average, and that the world is warmer now than it has been for 600 years. In a National Oceanic and Atmospheric Administration (NOAA) report, scientists claim that "during the past few decades, global temperatures have persistently broken previous record highs every few years, but never to the extent observed in 1998. Each month this year has set all-time record high global temperatures. This is unprecedented, and is not likely to occur in a stationary climate." US Vice-President Al Gore, in support of reducing greenhouse gas emissions, recently stated: "This is a reminder once again that global warming is real, and that unless we act, we can expect more extreme weather in the years ahead." New Zealanders would agree, having experienced temperatures in May 1.2°C degrees above average. "We can expect the warm trend to continue through at least the winter period," says Jim Salinger, a climate scientist at the National Institute of Water and Atmospheric Research. As world temperatures increase, mass coral bleaching events are expected to become more severe, extensive and frequent, with a number of wide-ranging impacts. Increases in large-scale bleaching could lead to poorer-quality reefs with lower biological diversity compared to present coral reef ecosystems. In some areas, reef building could cease and reef structures disintegrate and disappear along with the whole reef ecosystem on which many fisheries and island economies depend. Coupled with sea levels which are projected to rise some 300 mm over the next 50 years, the lack of growth even collapse of coral reefs would open up low-lying lands to severe erosion by the sea. Most coastal human habitation, particularly in Pacific and Indian Ocean island states, is concentrated on unconsolidated sandy ground less than two metres above sea level, which will rapidly erode without reefs as effective wave barriers. Coral reefs are the most diverse marine habitats on the planet, and their degradation through coral bleaching as a result of global warming would be a major blow to the marine environment and reef-dependent economies. In Australia, the Great Barrier Reef contributes, directly and indirectly, over $A1 billion to the Australian economy every year. Any decline in the reef system and its aesthetic values would impact severely on tourism and related industries. Earlier this year the Intergovernmental Panel on Climate Change, a group of 2500 of the world's top climate scientists, sponsored by the United Nations, commented that "Australia's coral reefs, including the Great Barrier Reef, are among the region's most sensitive environments to sea-level and climate change." Long-term monitoring studies by GBRMPA, the Australian Institute of Marine Science, and various universities are keeping tabs on coral bleaching events on the Great Barrier Reef, and their research is helping people grasp the seriousness of the problem. But it does nothing to solve it. Only a willingness to limit the causes of climate change the burning of coal, oil and gas can do that.
In 1751, the abbe Nicholas-Louis de Lacaille set to work at the Cape of Good Hope cataloguing the stars of the Southern Hemisphere. Apart from Edmund Halley, who made a cloud-bedevilled expedition to St Helena in 1677, Lacaille was the first European astronomer to observe our skies. Not only did he observe "new" stars those below Europe's southern horizon but he also defined 14 new constellations and subdivided Ptolemy's unwieldy Argo Navis into four manageable parts: Carina, Puppis, Vela and Malus the keel, poop, sail, and mast. Amongst the 10,000 stars Lacaille accurately positioned was Eta Carinae in the great Carina nebula. This bright nebula is the largest naked eye/small telescope object of its type, and lies in one of the richest parts of the Milky Way. Here we are looking along the length of the Sagittarius arm of the galaxy a great sweep of gas, dust and star formation which spirals away from our Sun towards the centre of the galaxy. Apart from the splendour of this area, Lacaille noted nothing remarkable in Carina. Eighty years later, Sir John Herschel set up an observatory at Feldhausen, at the foot of Table Mountain. Using what had been his father's favourite instrument, the 18.5 in x 20 ft Herschelian the finest telescope of its time he conducted a complete survey of the southern skies. Local astronomers had already observed that Eta Carinae varied in brightness, and by 1834 it had dimmed in eight years from equalling Beta Centauri (mag. = 0.6), to that of Aldebaran (mag. = 0.9). But during Sir John's time at the Cape, Eta brightened rapidly to magnitude 0.4, and he made a famous drawing of Eta and the associated Keyhole nebula. By 1843, Eta had, after another short decline, brightened so much as to outshine Canopus, and was second only to Sirius in brilliance in the sky. Since it lies at a distance of about 7500 light years from Earth, this means that Eta was about 5,000,000 times brighter than the sun, and at this time it ejected material equal in mass to several suns. In spite of this unprecedentedly large loss of material, the star appeared to have been unaffected, and continued to shine as energetically as before. However, in late 1845 it started to dim, and 30 years later its magnitude was 6.8, below the limit of naked eye visibility. Thereafter it has behaved irregularly while generally dimming, until today its visual magnitude fluctuates around an unspectacular 8. But in judging the brightness of Eta Carinae our eyes deceive us, for we are seeing only a very small portion of the total electromagnetic radiation produced by this star. Our eyes are only sensitive to radiation with wavelengths from about 380 nm (violet) to 780 nm (deep red), but the range of radiation from Eta is from 0.01 nm (extreme X-rays), to 109nm (1 metre—radar/ radio wavelength). When the brightness at all wavelengths is summed, called the bolometric magnitude, it appears that Eta has dimmed hardly at all, for what we now see is not the star itself but rather the z hot but cooling envelope of material which it blew off during its explosive outburst in the mid-nineteenth century, and which is now radiating strongly in the infra-red. The "star" Eta Carinae is now the hidden core of a small, bright-emission nebula. The material of the nebula absorbs the star's light and re-radiates it in the infra-red band. Indeed Eta is the brightest source of infra-red in the sky outside our solar system. In 1944, the Argentinian astronomer Enrique Gaviola described the Eta nebula as "a shape resembling a homunculus with its head pointing north-west, legs opposite and arms folded over a fat body." The name "homunculus" has stuck, but the appearance is an artefact of ground-based observation, for, as a recent striking photograph from the Hubble Space Telescope Wide Field Planetary Camera shows, the Homunculus is actually two great expanding balls of high-temperature gas with a disc of material forming a collar about the neck joining them. In addition, around and beyond the limits of the bright nebula are the fading remnants of earlier mass ejections. going on?" The star(s) Eta Carinae are hidden from us in the depths of the Homunculus, and the only direct emissions from it/them which we can register are those at the radio end of the spectrum, beyond even infrared. Since the radiation from the Homunculus is powered entirely by Eta, lying within it, by monitoring and analysing these radiations in conjunction with the star's radio emissions we can make some reasonably informed guesses as to what is happening inside the nebula. One of the most powerful tools has been spectroscopy, the analysis of radiant energy wavelength by wavelength. From this we can determine what elements and compounds form the Homunculus, whether they are ionised, their temperature and their velocity towards or away from us, and much more. Latterly there have been three schools of thought about the nature of the heart of the Homunculus. Eta could be a single supermassive star, 100 and 160 times the mass of the Sun, making it perhaps the most massive star known. Such stars are the final stages in the evolution of massive stars, which end their short (as little as 10,000-year) highly energetic lives with a series of massive eruptions, revealing a naked core of burning helium as they evolve towards core collapse and a final supernova explosion. Others consider Eta could be a close cluster of about six massive stars, each of 20 to 40 solar masses. The third school sees Eta as a binary system of two 70-solar-mass stars in which the stars have highly elliptical orbits, but at closest approach are only twice the distance of Mars from the Sun apart. As they approach and swing past one another, their high-velocity solar winds collide to form a hot shock-front which produces an outburst of X-rays, one of the features of the observed spectrum. Evidence for a binary system was presented by Augusto Damineli, who discovered a five-year periodicity in Eta's spectral changes. Although there are variable stars, such as the Miras, which pulse with periods of 300 to 600 days, there is no known class of variable stars with a period anywhere near as long as 2000 days. However, periods of this order are easily explained if Eta Carinae is a binary system. Yet even this explanation requires that the orbits of the two stars be aligned in a somewhat unlikely manner. Observations made at the end of 1997 and during the first quarter of this year may go far to resolving which of the models is the most likely . Thanks to Damineli's work, observers have for the first time been able to start their observations before the sudden and now known to be periodic changes in Eta's spectra, so we may soon be able to solve the enigma within the Homunculus. And it may well be in the nick of time, for the lives of super-massive stars are short, and their demise as sudden as it is violent.
Scenes from a Falcon's Nest
The hills and mountains of New Zealand have a profound effect on the country's weather. For example, when rain-hearing winds blow from sea to land, the upward motion of the air over the hills can cause 10 times as much rain to fall on high ground as at the coast. Once the air has passed the crest of the ranges, it descends and warms, evaporating most of the water in the clouds and creating a rain shadow in the lee of the hills. Because the prevailing wind in New Zealand is from the west nearly perpendicular to the main ranges conditions are relatively dry in eastern areas, from Gisborne to Otago, while western areas are wet enough to sustain rain forests. But this is not the only way in which wind and mountains combine to produce rain. Often, instead of rising over the land, the air splits into two streams that flow on either side of the ranges, then wrap around the end and collide with each other. (Ocean waves do much the same thing, rushing up a beach then washing round a rock, the two streams joining up again behind it.) Where the two air streams converge, some of the air is forced upwards, creating a line of cumulus clouds. These produce rain if the middle atmosphere is cold enough to allow the clouds to grow tall. Such an event took place on August 20, 1997. A southerly air stream was split in two by the Southern Alps. One stream spread up the east coast of the South Island, burst through Cook Strait and headed towards Taranaki. The other flowed up past Westland and Bullerverged, over the Tasman Sea just west of Taranaki, a line of tall cumulus and cumulonimbus clouds formed. These can be seen lying north-east to southwest on the 11 A.M. satellite picture . Cloud-top temperature was minus 42°C, indicating a cloud-top height of around 7500 metres and the likelihood of thunderstorms. After 11 A.M., the line of cloud pivoted about its midpoint. The eastern section moved south-east over the central North Island, dropping 24.8 mm of rain on New Plymouth airport between 4 P.M. and midnight, and delivering 31 lightning strikes in the vicinity between 4 P.M. and 7 P.M. Once the cumulonimbus had passed the high ground between Mt Taranaki and Mt Ruapehu, the clouds began to weaken as the air descended, and had mostly dissipated by 3 A.M. the following day. The western portion of the cloud line, meanwhile, moved northwards, retaining its cold tops and probably its vigorous thunderstorm activity for more than 24 hours. It finally weakened around 6 P.M. the following day, when it lay just west of the northern tip of the North Island. Convergence of low level air plays a major role in the formation of cold and warm fronts. However, in a front the two convergent air masses have different characteristics one warm, moist and less dense, the other cold, dry and more dense. By comparison, the sort of convergence described above brings together two air masses of similar origin and characteristics. Such zones tend to be shorter-lived than fronts and usually produce much less rain. Sometimes, however, the rainfall is phenomenal, particularly if the zone is moving slowly over a favourable location. Such a downpour occurred on December 20, 1976, in a convergence zone that ran along the hills west of Wellington and extended up the Hutt Valley. More than 300 mm of rain fell in 24 hours over much of this area the kind of deluge expected, on average, only once in 100 years or more. Much of the rain actually fell in less than 12 hours, making it more like a oncein-700-years event. Flash floods metres high roared down steep gullies where ankle-deep creeks normally ran to the harbour. Miraculously, no one was killed by these torrents, although the Hutt motorway was severed and hundreds of workers had to be rescued by helicopter from the roof of a factory cut off by fast-moving flood water from the Korokoro Stream. Many vehicles were destroyed, some crushed almost beyond recognition. The rain caused numerous landslips. A three-year-old boy lost his life when the side of a hall in Croften Downs collapsed under the weight of a wall of rocks and earth sliding down a hillside, while in Stokes Valley a number of houses were crushed or driven from their foundations by slips. A state of emergency was declared in the Hutt Valley, with many people having to be evacuated from their homes. Damage was estimated at $30 million. The narrow convergence line that caused the flood formed in a trough of low pressure over central New Zealand. A light southerly wind was blowing up the Kaikoura coast while a light northerly was blowing down the Kapiti coast. These two low-level winds converged over the Hutt Valley and the hills west of Wellington. The air in the trough was unstable, causing deep cumulonimbus clouds to develop, and heavy rain commenced. The upward flow inside the clouds was so strong it sustained and reinforced the low-level inflow, thereby setting up a feedback mechanism between the clouds and the convergence zone, which maintained and intensified each other. Furthermore, the way in which the heaviest rain followed the line of the hills suggests the cumulonimbus became anchored over the hilltops for a time probably because the surface northerlies on one side of the range and the southerlies on the other were deflected upwards by the rising ground, focusing the upward flow near the ridge line. Eventually, the trough over Wellington moved slowly to the east, allowing the southerly winds to prevail. The convergence line broke up, the cumulonimbus began to dissipate and the heavy rain eased off. Forecasting the location and intensity of convergence zones is difficult, especially more than 24 hours in advance. In most cases, computers now do a good job of tracking highs, lows and fronts several days into the future, but convergence zones usually slip between their electronic fingers. One reason is that such zones are generally smaller and of shorter duration than features such as fronts. Another reason is that they often owe their existence to subtle interactions between wind and land, so a computer needs a good description of an area's topography tucked away in its programs. This is something the global models that forecast the state of the atmosphere around the globe a week in advance do not have they rely instead on a relatively coarse interpretation of the landmasses. One solution to this problem is to use a second computer model, covering only a fraction of the earth's surface, but in more detail, while using the predictions of the global model as a starting point. The National Institute of Water and Atmospheric Research (NIWA) is experimenting with such a "meso-scale" model, which is being run over an area of several thousand kilometres' radius centred on Cook Strait, with data points about 40 km apart. This is about half the spacing of the global models, and therefore requires about eight times as many computations per square kilometre. The meso-scale model also has a more sophisticated physics package than that of the global model, being better able to keep track of heat variations as water changes from gas to liquid to solid and back again. Among the advances this model should lead to is an improvement in the forecasting of snow levels. When a snowflake reaches air with a temperature above zero, it absorbs heat from the air and melts. This lowers the air temperature, allowing the next flake to descend further before it encounters air above zero temperature. The net result can he a lowering of the freezing level by as much as 700 metres more than that which the global models predict MetService forecasters are working with the NIWA researchers to gauge how accurate the predictions of the meso-scale model are. In particular, in severe weather conditions of heavy rain and damaging wind, they will assess what advantage there is in running the model with only 20 km between data points, or applying the model over a larger area—both of which require a lot more computer time. Recent radar studies over North Carolina have detected convergence zones initiating and controlling most so-called random thunderstorms. Some of these zones are formed by interaction between wind and land, others by the leading edge of a sea breeze pushing in from the coast—a frequent occurrence in New Zealand, especially when two sea breezes from opposite coasts converge, as they can do over Auckland and Northland. Forecasting the precise location of thunderstorms is well beyond the capabilities of current models. Predicting the site of convergence zones caused by the interaction of wind and land, however, should be possible using the meso-scale model, if not with 40 km between data points, then at 20 km resolution. As each new advance in computer technology increases our number-crunching capability, it will be fascinating to see what further secrets we fathom in the mysteries of the weather.
Mike Mullord used to sell fish around Marlborough out of a distinctive customised van. His reflections on the life of a fishmonger first appeared in Seafood New Zealand.
Esteemed for both its gastronomic virtues and the surreal beauty of its shell, paua is our mollusc supreme. But pressure on the resource-especially from poachers-means that the days of gathering a free feed of shellfish from the rocks may be numbered.
In a succession of difficult postings—South Australia, New Zealand, South Africa—the energetic George Grey proved himself one of the British Empire's most able governors. Yet when he returned to New Zealand in 1861 for a second term, the magic was fading. The colony was on the brink of civil war, and local politicians were unwilling to allow Grey his former power. As an escape from the increasing pressure and frustration of public life, Grey purchased Kawau Island, building a grand house there amid exotic gardens and filling it with treasures. On the centenary of the death of Sir George Grey—soldier, statesman, explorer, philanthropist—we pay a lingering visit to Mansion House.
In an age of social fragmentation, what holds communities together--especially immigrant communities, people who, by choice or under durees, are living far from their homelands? For many, worship provides solace, strength and a sense of shared identity when they live as sojourners in a strange land.
Crimson pohutukawa fringing azure seas, a rugged mountain chain rising into the clouds and, at journey's end, a shady hideaway beside a peaceful estuary. These are the elements that make the Coromandel a place apart. Yet all is not sunshine in this slice of paradise. Making a living here is getting tougher, and as city-dwellers from nearby Auckland and Hamilton seek to partake of the area's tranquillity, people-pressure threatens to corrode the Coromandel's natural charm.
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