The UFO experience in New Zealand
Over the last century, New Zealand's natural habitats have come under great pressure from a wide range of introduced plants and animals. Much has been written about the demise of our forests as a result of browsing animals such as possums and deer. Dwindling numbers of native species such as kokako, kaka and kereru (pigeon) have been directly attributed to the voracious appetites of stoats, cats, possums and rats. Introduced plants, some of them garden escapees, are choking large tracts of bush and wetlands. Many species, including Clematis vitally and Kahili ginger, are extremely difficult to eradicate. Sadly, this phenomenon is no longer restricted to terrestrial habitats. Increasingly, many estuaries and saline wetlands are being invaded by the insidious Spartina, or cord grass. Spartina is a perennial rhizomatous grass (meaning that it has a horizontal, underground stem that sends out roots and shoots from its nodes) which can grow up to a metre tall. Two species and one hybrid exist in New Zealand. Of these, the one with the greatest ability for natural spread is S. anglica as it readily disperses by seed. Widely promoted for its sediment-trapping ability, Spartina's potential use for estuary reclamation created a worldwide enthusiasm for planting in the 1900s. By using Spartina it was envisaged that reclamation costs would he reduced. Spartina was introduced to New Zealand around 1913. Plants of a sterile hybrid obtained from Southampton were planted in the Manawatu River estuary near Foxton in an effort to reclaim land for grazing. This planting was extended in 1924, when culms of fertile seed of S. anglica were also planted. These Foxton plantings formed the stock later used to colonise other areas. S. alterniflora from the eastern United States was introduced in the 1950s, and Spartina is now established in many estuaries throughout the country. But there arc substantial concerns about the plant. Water catchment authorities arc worried about how Spartina perturbs natural water flows. Its dense form of growth and associated sediment-trapping can result in raised flood plains and restricted waterways. Fields of densely matted knee-high Spartina significantly reduce the intertidal area available to wading birds wanting to feed, and are also unsuitable for rails and crakes that prefer more open native vegetation. Even flatfish habitat is reduced, and the coarse grass encourages incursion (and contamination) by grazing cattle. Spartina also invades and alters the character of indigenous plant communities such as those found in mangrove and saltmarsh. In the Kaipara Harbour, single plants have been recorded as spreading at a rate of 50 square metres in four years. Spartina is now classified as a noxious weed and legislation is in place to prevent it from being planted. The problem, though, is how to control it. A number of methods have been tried. Herbicides have been applied by hand and air and from boats. Other forms of control have including digging out, steam treatment and the use of weed matting. Gallant, a grass-selective herbicide, has been found to be the most cost effective. Moderately toxic to marine invertebrates in a laboratory situation, field studies have revealed that it is quickly diluted by the tide, thereby minimising actual toxicity problems. However, researchers caution against the widespread use of Gallant until its effects on non-target indigenous plants have been fully determined. Few other techniques tried to date have proven very successful. If plants disintegrate after control measures have been applied, viable floating rhizomes may quickly re-establish. Control work has to be carried out between tides, limiting the time which can be spent on the task. One area where Spartina eradication is being vigorously pursued is the Bay of Islands. Volunteers from the Bay of Islands Coastal Watchdog group began trying to clear the weed from Uruti Bay, near Russell, in 1995. Spartina alterniflora had infested 300-400 square metres of mudflats, probably seeded from floating rhizomes arriving from elsewhere in the Bay. Herbicides were ruled out by the presence of shellfish beds and oyster farms nearby, so the first stage of the control programme involved the assessment of all known nonchemical control methods, including steam treatment, weed matting, burning, suction, dredging and hand removal. A combination of cutting the leaves and burning the base of the shoots near the mud was found to be the most effective. The treatment leaves no toxic residue, and the burner causes only incidental damage to non-target species. The second phase of the project will involve determining how often the burning needs to be done to prevent regrowth and kill the underground rhizomes. Unlikely as it sounds, burning a maritime weed may prove to be the best control method in some situations—a method which could be gainfully adopted elsewhere in the country.
Every year between January and May the East Australian Current delivers an influx of unusual marine visitors to New Zealand waters. Among them are several species of marine turtle, sightings of which are becoming increasingly common. Some 250 species of turtle are known, most occurring in tropical zones. Large land-dwelling species are often referred to as tortoises, while those that are hard-shelled and aquatic are called terrapins or turtles. Structurally, turtles are unique in the animal kingdom. The upper shell, under which the head, limbs and tail can be more or less completely withdrawn, is called the carapace. The lower, flatter shell is termed the plastron. The two parts of the shell are connected to the vertebrae and a series of expanded ribs. These anatomical features, along with the unique placement of limb girdles inside the rib cage and the possession of horny beaks instead of teeth set turtles apart from other reptiles. Marine turtles have long flippers which enable them to migrate over great distances, often averaging speeds of between 20-30 kilometres per hour. One juvenile leatherback turtle was clocked at 40 kph. Seaweed and jellyfish form a large part of the diet of marine turtles. Perhaps to handle such gelatinous fare, the mouth and esophagus are lined with rubbery protuberances resembling the open arms of sea anemones. However, like other reptiles, turtles have dry, scaly skin and a body temperature that is much more dependent on ambient conditions than our own. The leatherback is able to withstand much colder sea temperatures than can other turtles, due to its ability to maintain a body temperature which is up to 5°C warmer than sea temperature. Like almost all reptiles, turtles lay eggs. Typically, the female comes ashore on a sandy beach, where she may lay several clutches of a hundred or more eggs in holes she excavates. She then refills the holes and departs. Depending on the species, incubation time ranges from six weeks to more than seven months. Hatched by the heat of the sun, young turtles dig their way to the surface and then trek to the ocean. Only a small percentage of each clutch reach maturity. Predators and turtle hunters take their toll, and others are drowned in fishing nets. Nesting grounds are also diminishing as a result of coastal development. The trade in live turtles and turtle products doesn't assist the creature's survival. Stuffed specimens, shells, shell carvings, skins, leather articles, meat, eggs and oil form the basis of a thriving industry. This combination of factors has led to all species of marine turtles becoming endangered. In recognition of their plight, they are protected under the International Convention for the Trade in Endangered Species (CITES). However, many countries do not recognise CITES, and marine turtle numbers continue to decline. For instance, the number of loggerheads nesting fell by up to 80 per cent in the 10 years prior to 1993. In the Solomon Islands, 18,650 kilograms of tortoiseshell was exported between 1983 and 1990, before the enforcement of a trade ban. That quantity represented 20,000 turtles. In an attempt to prevent the extinction of these creatures, the South Pacific Regional Environment Program (SPREP) is coordinating a study of the migration and life cycle of marine turtles in the Indo‑Pacific Region. In New Zealand, records of turtle sightings are held on the Biosite database maintained by the Department of Conservation. There are some 160 records dating back to 1885, when a loggerhead turtle was observed at the entrance to the Manukau Harbour. Five species of turtle have been sighted in New Zealand waters, and 60 per cent of sightings occur in Northland. By far the most common species reported is the leatherback. Generally only seen at sea, this species—the largest in the world—can weigh up to 970 kg and measure three metres in length. As its name suggests, this species lacks a top shell, having instead a rubbery skin. Four species of much smaller hard-shelled turtles (rarely exceeding 1.5 metres in length) account for the remainder of the sightings, and are the species likely to he encountered on beaches. They are difficult to tell apart. The best keys to use are colour pattern and the number of costal shields, or plates, on the upper shell and head. The green turtle (named for the colour it imparts to soup, not for its body colour) has four pairs of costal shields and one pair on its head. The loggerhead—brown to dark brown in colour—has five pairs of costals and two pairs on the relatively small head. The olive ridley, of which there have only been a handful of sightings, is olive-green and has the same shield configuration as the loggerhead. The hawksbill possesses distinct overlapping shields, except in old animals where they are side by side. It has four pairs of costals and two pairs of prefrontal shields on its head. Its shell is a wonderful mix of strongly marbled shades of brown. Equal numbers of turtle sightings around the New Zealand coast have been at sea and on beaches. A number have been found entangled in lines and nets, and many of these have drowned. Those still alive are generally in an emaciated state, having been too long in waters that are colder than they can readily endure. Typically, they feel very cold to the touch, with baggy skin and eyes that are recessed far into the sockets. Often they will also be covered in seaweed and algal deposits as a result of not being able to swim fast enough to deter growths. Kelly Tarlton's Underwater World in Auckland has been rehabilitating stranded or trapped turtles since 1985. Turtles from as far away as Christchurch have been delivered to the aquarium, where they are gently rewarmed and rehydrated. Many are diagnosed with pneumonia and are often unable to float. They are placed on a foam mat in a special tank that has warm water underneath it and warm water above, dripping on to the shell. An artificial jelly-like mixture consisting of vitamins and mussels is fed to the animal until it is restored to normal health. It is then released into one of the main tanks, where it dines on greens, herrings and mussels. Recuperating in the aquarium at present are a green and a loggerhead. The average stay is six months. The turtles are then tagged and transported back to their native waters courtesy of naval or cruising ships sailing to Raoul Island and beyond. The most recent release was in May 1997, when a young hawksbill found at Glinks Gully in Northland was sent on his way. Marine turtles need all the help they can get. If you see a turtle, alive or dead, look for a tag on its flipper, record its location, try and identify it or take a photograph and contact the nearest Department of Conservation office. If you are lucky enough to find a live turtle ashore, contact or take the turtle to the Department or Kelly Tarlton's. In most cases, the turtle will be able to be nursed back to health and, in time, returned to the sea.
One of the exquisite frustrations of editing a magazine like New Zealand Geographic is knowing that there isn't enough room to say everything one wants to say. We are information magpies, my associate Warren Judd and I, picking up all manner of shiny oddments of fact and anecdote in the course of our research. Many of these gleanings find their way into captions or sidebars, but most never see the light of day. They are consigned—often with palpable regret—to the status of also-rans. For, though we crave comprehensiveness, we also admit to the truth that less is often more. The spare sentence; the uncrowded image—these are as important as imparting that extra gem of knowledge. And yet it seems such a pity to keep our windfalls of discovery to ourselves. So on this occasion I've decided to dig into the discard file and pull out a few of the cuts that never made it. It was while looking through the archives at Prices foundry in Thames that Warren Judd came across something which aroused his curiosity: a series of cartoons, often drawn on the backs of other documents. He asked foreman Neil Howe about their creator. "Doug Barker—well, he was a fitter's mate, cleaner-cum-tradesman, degreaser, scrapper, crane driver—all those things. Hard to be more specific." Whatever else he may have been and done, almost every week—and on other appropriate occasions—this "pretty regular sort of guy" produced a beautifully executed cartoon. For the most part, they dealt with works personalities and their idiosyncrasies, or sometimes a company happening, such as an unusual order (railway wagons for Nauru, to be used as chicken coops!), and, every so often, a political subject. Such a pastime is hardly germane to a story about casting, but it speaks volumes about a camaraderie in working life that is a rarity these days. We were especially taken by Doug Barker's vision of what one of his fellow crane driver's dream chair would look like (below). This bobby-dazzler has control knobs taken directly from the crane's cab, and much more besides. Move over, Laz-Y-Boy! Historical stories are always a rich vein to mine, and the Tyree brothers proved to be no exception. We were intrigued to come across a reference to Fred Tyree in Enga Washbourne's account of early days in Golden Bay, called Courage and Camp Ovens. Locals had discovered a 12-foot swordfish dead on the sand at Pakawau, apparently the victim of its own three-foot sword, which was wedged into the sand right up to the hilt. Fred was notified to come and photograph the spectacle, but never materialised. A few days later, when asked why he hadn't come, he replied that, as the request came on April 1, he thought it must have been a practical joke. The tales Derek Grzelewski told us in the course of his research on caving tended more to the macabre, but they greatly increased our respect for these adventurers of the underground. One story involved three Austrian students at the end of last century. Foolishly, they carried only one light source (modern cavers insist on having three). When the light died, they were near a side wall of the cavern they were exploring. Beyond them, all was black and empty space. Thinking to retrace their steps, they all kept one hand on the wall and lit a match every now and then to guide them. Their bodies were found a short distance from a circular trail of spent matches: they had been walking round and round a column 16 metres in diameter before giving up in despair. Then there was the story of Floyd Collins, who languished for two weeks wedged in a Kentucky cave while bungling attempts were made to dig him out. He died of starvation and exposure before rescuers reached him. No doubt such stories came flooding back to Derek as he tried to thrust himself through some of the more difficult cave "squeezes" he encountered during his field work. He later commented that the ideal caver would be a "spineless midget contortionist, equipped with gills and webbed feet, and, like a glowworm, generating its own light." On a more constructive note, we learned how Auckland geographer Peter Crossley, the original compiler of the Atlas of New Zealand Caves, earned the nickname "the stal doctor." A noteworthy stalagmite in Waipuna Cave in Waitomo was accidentally knocked over, and broke into a dozen pieces. After obtaining permission from the Department of Conservation, Peter removed the chunks of calcite, cleaned them up and glued them together with epoxy resin. He then laboriously transported the two-metre speleothem back into the cave and reinstalled it. It is from such fragments as these that all insight is born.
Mars has always fascinated humankind. Its baleful colour and striking hundred-fold variation in brightness, from second only to Venus to dimmer than amma Crucis, the star at the head of the Southern Cross, make it remarkable amongst the planets. Also, as the Earth swings past it on the inside track, for a while Mars appears to reverse its movement against the stellar background. In 1666, Cassini established that the length of the Martian day was only 40 minutes longer than that of the Earth. This was a powerful inducement to believe that the planet would prove to be similar in other respects and therefore support life. A century later, the "Mars is a little Earth" school received an enormous boost when William Herschel, using his excellent reflecting telescopes, discovered the polar caps and their seasonal variations which march with colour variations elsewhere on the planet. He also determined that the obliquity of the Martian ecliptic is within a tad of that of the Earth, 23°44', and to cap it all, observed evidence for an atmosphere. Only the fact that Mars was smaller than the Earth prevented it from being an identical twin. In 1877, when Mars was at opposition and only 56 x 11:30 kin from us, Schiaparelli discerned a number of fine, straight markings on the surface. In his report he called these cattail, or channels, but only too easily the translation became "canals," and as such the first evidence of alien constructions on this most likely home for alternative life forms. At the same time, Asaph Hall discovered the two moons of Mars, which had apparently been foreseen by Jonathan Swift in his Gulliver's Travels. Although many astronomers failed to confirm Schiaparelli's observations, the wealthy and gifted amateur astronomer Percival Lowell was not among them. Fired with a belief in Martian life, he built the observatory at Flagstaff, Arizona, for the express purpose of observing Mars. With a 24-inch refractor, the biggest of its time, he made thousands of observations and a multitude of drawings and photographs. With these data he constructed maps and globes of the planet showing more than 200 "canals," many paired and all so straight as to argue that they must be artificial constructions. From here it was but a step to his picture of an intelligent race trapped on a slowly desiccating planet, bending their efforts to channel the remaining water from the melt of the polar caps to their cities. If the public needed anything further to fix its attention on Mars, The War Of The Worlds by H. G. Wells was to supply some of the most memorable bug-eyed monsters ever to challenge the assumption of human superiority. These Martians were the antithesis of Lowell's pacific, globally co-operative race struggling for survival, for Wells' creatures, faced with the same threat, used their technological superiority for conquest. In spite of the commissioning of the 100-inch Hooker Telescope on Mount Wilson during World War I and of the 200-inch Hale on Mount Palomar after World War II, Mars could not be seen well enough through our atmosphere to settle the question of it supporting life. By then, only the most dedicated Lowellites continued to "see" canals, and spectroscopic analysis painted a picture of a dry, frozen and almost airless planet. But Mars continued to fascinate, and inspired in Ray Bradbury's Martian Chronicles some of the best science fiction short stories ever published. The first clear look at Mars came with the fly-by of Mariner 4 on July 14 1964. Mariner photographed only one per cent of the planet's surface, but this was enough to consign Lowell's canals to the archives of optical illusion, for what was revealed was a sterile, cratered surface, apparently similar to that of the Moon. Five years later, Mariners 6 & 7 made low-altitude flybys and confirmed that Mars was barren. Then, in November 1971, Mariner 9 went into orbit around the planet and photographed the entire surface. We saw not just craters, but for the first time great volcanoes, chasms far larger than any on Earth and, most surprisingly and significantly of all, sinuous channels which had every appearance of being wadi: dry river beds. If indeed this is what they are, and no reasonable alternative has been proposed, then Mars must once have had substantial amounts of liquid water, and so the possibility of life. Following the Mariners came the Viking orbiter/ landers, the most complex interplanetary spacecraft yet launched. On arrival in July and August 1976, Vikings 1 & 2 went into orbit around Mars, and both released a lander unit which made a soft landing and relayed back physical data, photographs and the results of life-detection experiments. The photographs confirmed a desolate landscape of sand and rock, and the search for signs of life yielded at best equivocal results. However, the failure to confirm any evidence of life in a few grams of desert sand is not conclusive a small random sample from the Sahara or Gobi is not likely to do any better. It was not until September 1992 that the next spacecraft, Mars Observer, lifted off on its 11-month journey to go into orbit and perform a global survey of the surface and atmosphere. The six instruments it carried were to map the whole planet topographically, geologically and meteorologically, but, at the last moment, probably while making an automated braking manoeuvre, contact with the craft was lost and never regained. Five years later, a fleet of three space craft was launched with a range of instruments and experiments designed to make up for the loss of Mars Observer. Unhappily, the biggest and most elaborate of them, the Russian Mars 96, was lost when the upper booster failed and the space craft was destroyed over the Pacific. Of the two remaining craft, NASA's Global Surveyor is on course and functional, and, as this issue goes to press, Pathfinder has landed and become a focus of world attention. Pathfinder's job was to get the remote-controlled Sojourner vehicle on to the surface, where it is being used to test command and control technologies as well as take high-resolution close-up photographs of selected objects, together with X-ray spectrographs which will reveal chemical composition. Global Surveyor, due to arrive in September, will photograph the surface at a resolution of three metres—just fine enough to spot the Vikings—while its spectrometer and laser altimeter will carry out the meteorological and topographical mapping originally intended for the ill-fated Mars Observer. Both spacecraft have been designed, built and programmed under rigid financial constraints, and this has meant abandoning elaborate, fuel-expensive braking manoeuvres. For Global Surveyor, this means being slowed down by a single 20-minute burn from its engine, to place it in a highly elliptical orbit, and then its specially strengthened solar panels will act as air brakes. As the craft dips into the upper levels of the Martian atmosphere, each successive skim past the planet will slightly slow it. One hundred and thirty days of this deceleration will bring the craft into the required circular polar orbit. Pathfinder approached Mars without any preliminary braking manoeuvres, crashing through the atmosphere on July 4 behind a Viking-type heat shield, and then deployed parachutes and airbags on which the lander bounced to a stop. Three "petals" shrouding the lander opened to allow Sojouner, the 11.5 kg microrover, out on to the surface for a few weeks of exploration—at a speed not exceeding a sedate 40 cm per minute (see map below). If Global Surveyor and Pathfinder/Sojourner perform as intended, they should pave the way for later instruments which may settle once and for all the question of whether life exists or has existed on Mars. To some, meteorite ALH 84001, the Antarctic rock which caused such a stir last summer, has already answered this question in the affirmative, but others doubt the reality of "bacteria" only 0.01 times the size of their terrestrial counterparts. For others, the so-called "Face on Mars" is evidence of not only life but civilisations past. The "face" is no more than a trick of the light, and as the direction of the sun or the angle of view changes, so the face disappears. (A number of such phenomena are known on Earth, including-the Duke's Head in Whangaroa Harbour.) The questions of life, its origins, its varieties, its chemical construction and processes, cut to the bone and always engage us. Is there life elsewhere? How common is it within our section of the galaxy? Is there only one basic sort? Do the strange fossil forms preserved in the Burgess Shales represent inherently faulty organisms, or were they extinguished through some outside agency such as a massive asteroid impact, so that elsewhere they became the precursors of forms unimaginable? Are there other intelligences? There are cogent arguments supporting the claim that only a C, N, H, 0 and liquid water-based system can support life—that only this combination can provide the stability and energy transfers for the huge molecules which are essential to life processes. But this is not to say that all life chemistries must be identical. All earthly DNA employs the four-letter code of adenine, cytosine, guanine and thymine. Are these the only possibilities, or has some analogue of "our" DNA evolved using different bases? All being well, the results of these current missions will be encouraging enough to justify an international mission in the next 10 years to return samples of Martian soil to Earth. Fossil remains of bacterial colonies on the surface, even if hundreds of millions of years old, will lend support to the idea that there may yet be subterranean life where there is liquid water and compounds to metabolise. Such habitats would be analogous to the "black smokers" along the Earth's ocean ridges, those fountains of mineral-rich water which support communities of bacteria and complex organisms. But it may be that Martian life could not evolve fast enough to adapt to the cooling surface and loss of atmosphere, so that only fossils remain. But if there is or has been life on Mars which is in some way radically different from our form, then the "seeds from outer space" theory of Fred Hoyle, amongst others, appears less likely than that of spontaneous development. On the other hand, should Martian life prove to have the same chemistry as Earth's, this would lend support to theories which argue a common origin—but equally may merely demonstrate that there is only one life chemistry. One thing is certain: evidence of any sort of Martian life will have as big an impact as did the publication of The Origin of Species.
Suspended between two worlds, a caver ponders the enormity of Harwood's Hole—one of the grander entrances to the unseen labyrinths that riddle the marble mountains of north-west Nelson.
Around 45,000 years ago, when our ancestors were neighbours to the Neanderthals in Ice Age Europe, there was a kahikatea tree growing beside a stream which flowed out of the eastern side of the Rimutakas. Erosion being very active during the Ice Age, the stream carried large quantities of shingle out of the ranges when it flooded. In one flood, the base of the tree was covered in shingle about half a metre deep. Yet it survived and grew a second set of roots on top of the new surface. However, as more shingle was dropped by subsequent floods, the tree died and was eventually completely covered by stones. Today, during what is a warmer interglacial climate, a stream is cutting down through the shingle deposits and the kahikatea tree is emerging again into the light. Its top has disappeared and its surface is deeply cracked, but it is still upright and easily recognisable as a tree. What is amazing is the depth of the layer of shingle above it. Measuring 40 metres in places, it is testimony to the extent of erosion during the last Ice Age. Erosion was vigorous during the Ice Age for several reasons. First, the cold conditions caused the tree line and the altitudinal limit of other vegetation to fall to much lower elevations than they are today, exposing underlying rocks to weathering. Second, the weathering processes then were more severe than they are today. Sunlight was almost as intense as it is nowadays, so its ability to heat rocks was similar. However, the average air temperature in New Zealand was more than 5°C below today's values, so the overnight minimum temperature experienced by rocks would have been much lower. Consequently, thermal stress as the rocks expanded and contracted would have been greater, and the rocks more prone to shattering. The onset of the Ice Age seems to have been a protracted affair. Go hack 50 million years to the Eocene and Antarctica was much warmer than it is today, covered largely by forest even though it was near the South Pole. Things began to change as continental drift gradualh altered the pattern of the world's ocean currents and restricted their ability to deliver heat to polar latitudes. The cold intensified in the south some 25 million years ago when the continents of Australia and South America moved far enough away from Antarctica to allow circumpolar currents to develop in both the ocean and the atmosphere. Cut off from warm waters of tropical origin and the weather systems they had brought with them, Antarctica cooled and developed an ice sheet with glaciers extending to sea level. Some time later, the continent of India collided with Asia. As India pushed north into Asia, the Himalayan mountains were created and the Tibetan Plateau raised up. About this time, the Rocky Mountains were also lifted up. Both these great obstacles diverted the westerly flow of the atmosphere, causing cold air of Arctic origin to flood south more frequently and to a greater extent than previously. Finally, between two and three million years ago, North and South America were joined together by the isthmus of Panama. This sliver of land blocked the warm ocean current that flowed westward along the Equator and diverted its waters northwards to join the Gulf Stream off the east coast of North America. Evaporation was high when the water was in tropical latitudes, and as the water became saltier it also became denser. Consequently, as it moved polewards through the North Atlantic, the water began to sink below the surface earlier in its journey and no longer carried as much warmth to near polar latitudes. This allowed the formation of large ice sheets to begin over Europe and North America, and it is at this time that most commentators consider the Ice Age to have begun, with global average temperatures dropping as much as 4°C below today's level. The closing of the land bridge between the Americas caused another great upheaval, as it allowed animals from both continents to migrate to the other. North America gained possums, porcupines, monkeys, armadillos and sloths from the south, while South America gained rabbits, dogs, horses, pumas, and llamas from the north. Many of the large animal species in South America became extinct after the exchange, but this may have been because of climate change as much as conflict between species, since animals as diverse as the horse and the mastodon became extinct on both continents. Global average temperatures have not been uniform since the onset of the Ice Age, but rather have fluctuated on a scale of about 100,000 years between warm interglacials, such as the Earth is in now, and full glaciations, when the average temperature drops by more than 4°C. The driving mechanism for these changes seems to be small cyclic variations in the Earth's orbit around the Sun. If you can imagine driving a large knitting needle through the Earth along its axis of rotation from the North Pole to the South Pole and then standing back to admire your handiwork, you would see that it made an angle of 23.5 degrees with the plane of the Earth's orbit around the sun. This tilt is what causes the seasons. If the needle were perpendicular to the plane of the orbit, there would be no summer or winter, but only a kind of permanent spring. In fact, this angle varies from 22 to 25 degrees in a cycle that repeats every 40,000 years. Also, the Earth's orbit around the sun is not a circle but an ellipse, and the ellipticity varies with a regular cycle of 100,000 years. Further, there is a slow precession in the Earth's orbit, like the wobble of a spinning top, that takes about 22,000 years for each wobble. This has the effect of varying the time of the year when the Earth is closest to the Sun. At present, this closest proximity occurs during January, which is one reason why it is easier to get sunburnt skin in a southern hemisphere summer than in the north. In another 11,000 years, the Earth will be closest to the Sun during a southern hemisphere winter. All three of these effects combine to vary the intensity of sunlight reaching the Earth's surface. However, the variation is not large enough on its own to explain the fall of temperature during a glaciation. A feedback mechanism is needed. One of the most important is the way a snow or ice surface can act as a mirror and reflect most of the incoming sunlight back into space. Once a large part of the Earth is covered in ice, a significant amount of the heating the Earth normally receives from the Sun is lost to space. The key to starting a glaciation seems to be the intensity of the summertime sunlight over the northern hemisphere. When it is relatively weak, there is more chance of a significant part of the winter snow cover on the land lasting through summer and helping the next winter's cover to be even more extensive. A runaway process can begin in which the snow cover expands sufficiently to start ice-cap formation. Another feedback mechanism involves the increased erosion that occurs during a glaciation. Some erosion processes take carbon dioxide out of the air. But carbon dioxide is an important greenhouse gas, helping to trap some of the heat the Earth radiates that would otherwise be lost tospace. The less carbon dioxide there is in the atmosphere, the greater the cooling of the Earth. Measurements of air bubbles trapped in ice drilled out of the Greenland Ice Sheet have shown a much lower level of atmospheric carbon dioxide during the last glaciation than just after it. Erosion and earthquake activity may also be connected. Increasingly, geologists see erosion as a significant force contributing to the uplift of mountain ranges. The rocks of the Earth's crust are less dense than the rocks of the Earth's mantle, on which the crust floats. Erosion can remove so much material from mountain ranges that the Earth's crust becomes locally lighter, and therefore more buoyant, just as unloading a boat causes it to float higher. That upward movement of the crust causes earthquakes. But the higher the mountains, the heavier the rain which falls upon them, and therefore the faster the erosion proceeds, causing more uplift and more earthquakes. During the several million years that the Southern Alps have been rising, they are estimated to have gone up by a little over 20 kilometres. Why, then, are they less than four kilometres high today? The missing 16 kilometres has been eroded away, forming, among other things, the Canterbury Plains.
Professional photographers whose work spanned nearly 50 years around the turn of the century, brothers William and Fred Tyree started what is now one of the most important pictorial archives in the country. The Tyree Collection is an extraordinary provincial insight into a colony struggling towards nationhood.
At the foundry of A.&G. Price in Thames, molten metal has been cast into everything from locomotives to pickaxes for close to 130 years.
We hear the birds even before we reach the island: a raucous, unconducted symphony of screeches and whistles. Tui, bellbirds and saddlebacks contribute to the sound, but it is the kaka that stand out: their calls, like their name, loud, staccato and unmistakable. A burst of red flashes out among the foliage as one lands on a branch nearby. Then a babble of even louder squawks erupts as another kaka drops in and a playful squabble ensues. One bird departs and the other, perhaps a mate, soon flies off in pursuit. Although only 20 minutes by boat from Paraparaumu, the wildlife sanctuary of Kapiti Island seems more like a different planet—one where birds rule. This happy state of affairs exists because, of the various introduced predators present on the mainland, Kapiti has had but two representatives: both rat species and both now eradicated by poisoning. Birds exult and thrive in the pest-free environment. Surf hisses and rattles on to the stony beach, washing over our boots as we leave the boat. Peter Daniel, Kapiti's resident Department of Conservation ranger, welcomes us to the island. As we enjoy a picnic lunch, an inquisitive kaka hops on to a branch overhead, giving us a sly sideways glance. Without hesitation, the bird flaps down and tries to steal a sandwich. We laugh at its impertinence. For the past 30 years, kaka and other birds on Kapiti have received supplementary food supplies. Daniel regularly replenishes a large trough of sugar solution near his house. Tui and bellbirds jostle for position on the edges of the tray, dipping in, then lifting their heads with the sweet water dripping from their beaks. The birds show neither fear nor apprehension, despite the dozen or so people chattering and looking at them. But the whirr of larger wings behind makes the smaller birds scatter as a kaka lands on the tray. Kaka indisputably head this feathered nation. The bird then perches on a woman's head, the better to steal a piece of cheese. As its claws scrabble for a hold in her hair, she grimaces in a mixture of pain and delight. Kaka are ridiculously easy to photograph here, as they preen and prance unafraid. There is no need for the stealth and cunning necessary to get within cooee of mainland birds. On the few larger forested offshore island sanctuaries, kaka scream, chatter, clown around and almost fall over themselves in their eagerness to interact with human visitors. Yet on the mainland, the behaviour of kaka is entirely different. The birds are rare, more often heard than seen, and largely indifferent to humans. Daniel has tramped in Whirinaki Forest every year over the last decade. "I always hear kaka in Whirinaki, but not once have I got closer than 80 metres to one. It is such a contrast to Kapiti." One Kapiti kaka could even be picked up by his beak, says Daniel. "He'd let you lift him up, screeching, play-fighting with his claws and pretending to be annoyed." For mainland kaka, every day is a fight for survival. The birds can spend up to eight hours a day just gathering sufficient food to meet their requirements. But the greatest threat to the birds is from predators over the period when females incubating eggs or rearing chicks are confined to their nest holes. As a result of this mortality, males can outnumber females by six to one. Peter Wilson of Landcare Research in Nelson has examined kaka populations on all our forested islands and compared the numbers of birds with the range of predators present on each island. Where there are no stoats, kaka populations are healthy, even if cats and rats are present. Wherever there are stoats, kaka are in trouble. On Kapiti, there are over 1000 kaka in 1500 hectares of forest. On d'Urville Island—at the same latitude and with 8000 hectares of forest, but with stoats as well—there are only about a dozen kaka left. Unless the predator problem can be solved, kaka will eventually be lost from mainland forests and islands like d'Urville. By contrast, on stoat-free islands (including Little and Great Barrier, Kapiti, Hen, Stewart, Mayor, Codfish, Ulva and Nukuwaiata) kaka populations are growing. Plenty of food and less lethal predators mean the birds are able to breed successfully. However, when these islands reach their carrying capacity and run out of room and food, emigrating kaka will have to face the dangers associated with mainland life. Kaka are members of the 330-strong parrot family, also represented in New Zealand by the flightless kakapo, the alpine kea (see New Zealand Geographic, Issue 24) and several species of parakeet. Along with their indigenous relatives, kaka have been in decline since the onset of human occupation, due to predation and competition from introduced animals, forest destruction and hunting pressure. Kaka are now restricted to larger forested islands, and North Island kaka are rarely found outside the large forest tracts of Pureora, Whirinaki, Tongariro, Urewera and Kaimanawa. South Island kaka are seen in moderate numbers in Fiordland, Mt Aspiring and Westland National Parks and are still common on Stewart Island. The kaka is a large bird, standing about 46 cm tall and generally coloured dull olive-brown. Its most striking features are a large arched beak, dark, inquisitive eyes, scaly feet and the scarlet feathers on the underwings. North Island kaka have less grey in the feathers on their heads than their South Island counterparts do, are a centimetre shorter and weigh 100 grams less. Accordingly, they have been classified as a separate subspecies, Nestor meridionalis septenrrionalis, rather than the Nestor meridionalis meridionalis of the South Island. Although kaka are the same height as their close relative the kea, kea weigh close to twice as much. Male birds are larger than females (South Island range: males 525-640 g; females 430-550 g) and their upper mandible is longer than that of female birds. Museum specimens show that white, yellow and red varieties once occurred. Kaka may live for up to 20 years, though on the mainland few will die of old age. Kaka feed on nectar, fruit, berries, seeds, insects and sap. They concentrate on one food, then move on to others as each comes into season. Much of their feeding takes place in the canopy, bringing them into direct competition with possums. South Island kaka also use their semi-brushed tongue to lick honeydew, excreted by scale insects, from beech trees. Unfortunately for kaka, honeydew is also favoured by introduced wasps, which compete with kaka for this high-energy resource. Research suggests that kaka satisfy their energy needs from nectar and honeydew, while seeds provide them with protein and insects and grubs with fats. The kaka uses its powerful beak to tear long strips of bark from trees in search of insects and sap. This destructive approach to feeding earned kaka the nickname of "tomahawk" in parts of Otago last century. To the annoyance of foresters, the "tomahawk" is quite capable of ring-barking pine trees. When sap-feeding, kaka make lateral incisions on the trunks of trees such as totara, northern rata and pohutukawa, licking up the sap as it oozes out. This type of feeding happens during spring and autumn; the timing is thought to be related to changing sugar levels in tree sap. After kaka have stripped bark in search of sap and insects, the tree is open to infection, often leading to decay and death. It is thought that when kaka were abundant they may have played a significant role in the renewal of the forest, hastening the demise of older trees and thereby making room for the young and vigorous. As nectar feeders, kaka also perform the associated role of moving pollen around the forest. [Chapter Break] Peter Wilson and a team of Landcare researchers have been studying kaka for more than 10 years in a possum-chewed, wasp-infested beech forest near Nelson Lakes National Park. Wilson believes that competition from possums and wasps for the same high-energy foods kaka depend on is limiting kaka breeding: "If kaka are denied high-energy foods in late summer and autumn, they will go into winter in poor condition and not reach breeding condition by spring." In addition, when a female is nesting, she relies on the male to forage for her, but if he is unable to procure sufficient food, the female will leave the nest to forage for herself, causing incubation failure. Wilson monitored 31 kaka for five years. During this time only two pairs attempted to breed and only two fledglings were raised—by one female. A year later, this female was killed, probably by a stoat. "Even for a long-lived parrot, successful breeding by one out of 31 kaka in five years is a mighty low reproductive rate," comments Wilson. So in 1989 he set out to investigate whether supplementary feeding would improve breeding success for kaka. However, unlike the feeding free-for-alls common on Kapiti, getting mainland kaka to accept supplementary food proved difficult: "We tried trays of honey, honey-water and huhu grubs. Nothing worked until we hung silk fuchsia flowers—imitating mistletoe, a favourite kaka food—in beech trees." Kaka immediately visited the flowers, and Wilson then trialled a range of food types in what he calls a "cafeteria experiment." Grapes, sunflower and pumpkin seeds, avocados, peanuts, honey, cheddar cheese, pine nuts, cashew nuts and a mix of Complan and Farex were all placed near the flowers. "Pine nuts proved a great hit, but they're outrageously expensive!" says Wilson. He also attached hamster feeder bottles containing honey-water to trees, with the nozzles coming out of poinsettia flowers. Supplementary food was made available daily to kaka from three automatic feeders, and Wilson says the experiment was "a crashing success." Of 23 birds monitored, 39 per cent fed regularly, 22 per cent fed sometimes and 39 per cent sampled the supplementary food only once. Older birds seemed reluctant to try new foods, he says, while younger birds tended to be attracted to novel things. Have kaka been imprinting on humans, perhaps? Of particular interest to the researchers was the behaviour of a bird nicknamed Knuckle (see sidebar; page 104). Soon after the feeding programme began, the 15-year-old bird was taught to use the feeders by his mate. "Knuckle has bred with several different females in his life, but none of their eggs have hatched. Only since he has used the feeders have the eggs been successfully incubated," says Wilson. Although supplementary feeding does not trigger breeding, Wilson believes it may put birds in better health, so that when the unknown stimulus urges them to breed, they will have a greater chance of success. The breeding success of kaka varies from year to year, probably in response to annual variations in food sources. Without honeydew, mistletoe and other high-energy foods now taken by wasps and possums, South Island kaka fail to reproduce. North Island kaka may be more reliant on sap and heavy podocarp fruiting to trigger breeding. Mating occurs in spring, and the females make primitive nests in deep holes in tree trunks. The nest lining is a mixture of wood fragments chipped and chewed from the inside of the tree. Between two and five dull white eggs are laid in a hollow amongst the debris and are incubated for 24 days by the female. The male returns periodically to provide food for his mate. Kaka nests only become obvious once the grey, downy chicks reach 10 days old, when the smell of faeces may be detectable from 10 or more metres away. Chicks remain in the nest for 10 weeks, growing adult feathers before emerging flightless and noisy. They can spend up to a week on the ground before their feathers are ready for flight. From the moment the eggs are laid to the time that the chicks can fly is a staggeringly long three to four months—a time when female, eggs and chicks are extremely vulnerable to predation. [Chapter Break] It is midwinter and we are in the middle of the expansive Pureora Forest Park, a towering jungle of ancient podocarp trees that constitutes one of the few remaining homes for North Island kaka. Despite Swanndris and balaclavas, we are shivering as we huddle beneath ferns with a team of kaka researchers. Compared with the numbers of kaka this forest once contained, today's population is pitiful, yet Pureora is one of the best places on the mainland to see these elusive parrots. Terry Greene, the crew boss, sits with his head back, eyes straining to see a kaka he knows is perched near the top of a rimu tree. Strung high among these giant trees is an almost invisible mist net. It has taken a full two days to erect the net. First, a suitable site is selected, where kaka are known to occur, and then a space for the net is cut in the forest floor and all small shrubs and ferns that might entangle the net are removed. Next, Alan Jones, one of the taller team members, uses his long arms to advantage with a slingshot. After several unsuccessful attempts, a fishing sinker with nylon attached is shot over an appropriately elevated rimu branch at one end of the clearing. Since some of these podocarp giants are 50 metres tall, it is a feat requiring Robin Hood prowess. The same procedure is repeated at the opposite end of the clearing. A thick rope tied to the nylon is then hauled across. From this rope, two more ropes hang vertically, with the net suspended between. Once hoisted aloft, the net floats near the top of the canopy, and a pulley system enables it to be raised and lowered quickly. The researchers hope to catch at least 20 kaka, attach radio transmitters to the birds and follow them through an aerial 1080 possum-control operation to check that they survive. Possums threaten this majestic forest, and the Department of Conservation is using carrots laced with the poison 1080 to make a dent in their numbers. The use of 1080 is a successful, if controversial method of possum control. There are fears that the inquisitive kaka could be at risk from eating poisoned baits. Research shows that some kaka, particularly juveniles, will eat baits, but hunger might tempt older birds, too. Attaching radio transmitters to the birds is the only sure way of knowing if kaka will survive the possum blitz. For the crew, finding even two dozen birds is a needle-in-a-haystack challenge. The monitoring area is 24,600 hectares, and the birds are wary, unapproachable and can easily fly 50 km in a day. They also like to play hide-and-seek with would-be captors. "Trying to catch one of these cheeky, screeching, elusive birds is difficult at best, and downright foolhardy at worst," says Greene. "What's more, they seem to learn from their mistakes. I've seen one kaka we've caught telling a new group about the dangers of mist nests in no uncertain terms!" High in the rimu, a kaka calls. Greene presses a button on his CD player, and from a speaker hidden up in the trees a recorded kaka call scraarks out. Above, the real kaka calls again. The CD responds with a whistle. The kaka remains silent, watchful, suspicious. We sit below, motionless in the biting cold, anticipating. Nothing moves. Greene conjures another whistle from his artificial kaka, quieter this time. A softer, social "howdee doodee" contact call. Silence. Then suddenly the kaka swoops from its perch towards the clearing. It descends, but is still above the net. It clears the top and lands on the opposite side. We're disappointed. The thought of capturing a kaka had set the adrenalin flowing. Still, we can hardly expect to be so lucky on our first day when the crew has spent weeks doing this. The chess game begins again, with Greene playing canned calls on another speaker at the far side of the net. Curiosity rather than aggression brings kaka towards a net, Greene explains. We move, the kaka moves; we wait, it waits, neither sure of what will happen. Today it's a stalemate. The kaka is curious but never flies low enough to chance getting caught in the net. After several hours in the numbing cold we give up. The net is lowered and carefully packed away. The fine filaments can be easily caught and tangled, creating a mess that takes hours to undo. It's a far cry from the days when one Maori hunter sitting in a tree could snare dozens and sometimes hundreds of kaka in a day. Catching kaka in Pureora is a military-sized project requiring military-like commitment from the crew, who work in 10-day stints, mostly camping or staying in huts within the forest. They have 500 kg of gear including tents, climbing ropes, harnesses, cookers, slashers, bird-banding gear, mist nets, pulleys, slingshots, tape recording equipment, speakers, a CD player, transmitters, food and packs. The gear is flown in by helicopter, and a base set up for the crew. Winter daylight is short. Wet and miserable or cold and freezing are the only weather cycles. Greene says some days it is so cold that the bananas freeze inside the hut. "Temperatures drop below zero, and when you are hunkered down under fern fronds at dawn, waiting for a kaka to call, you need lots and lots of clothing. About three layers of trousers and six layers of tops just about keep out the chill!" But the numbing cold is quickly forgotten when a kaka is caught. The crew swings into practised action, lowering the net and quickly removing the bird. It is a stressful time for both bird and captor. "You need to grab the head and feet to immobilise them," says team member James Fraser. "The beak is like a can opener, and the claws are just as lethal." Once out of the net, the bird is put in a canvas bag—the darkness helps calm it. Over the next half hour, measurements are taken of wing length, weight, tail length and beak dimensions. These measurements help determine the gender of the bird, as males are larger and heavier than females. Of the 21 birds eventually captured, only three are females—confirmation of the dire state of the mainland kaka sex ratio. The birds are colour banded and a radio transmitter fitted, using a thin braided-nylon harness around the bird's chest and wings. The harnesses are designed not to restrict the kaka while flying, and a weak link is built into each harness so that it will eventually fall off. Each transmitter emits a different frequency, giving each bird its own signal which can be tracked on the ground or from the air. On one occasion the crew captured four birds in rapid succession. "We had these four birds in canvas bags, pegged to a tree, looking like wriggling Christmas stockings," says Greene. "The only problem was they were all poking their beaks through the bags, trying to bite their way out. There is nothing like the imminent loss of a bird to speed the measuring process up!" Given the impenetrability of the forest, it is impractical to try and follow the birds entirely on foot. Instead, an aircraft flown by Sid Marsh, a commercial pilot as well as a member of the kaka crew, is used to skim low over the tree tops. Two large aerials attached to the plane's wings allow kaka to be followed through the forest, using a receiver in the cockpit. The birds' positions need to be determined frequently to ensure they are moving—and therefore alive. After following the birds for six weeks (at which time the 1080 carrots were no longer toxic) the crew were certain that all monitored kaka had survived—the best possible result and an enormous relief to everyone concerned. As far as kaka are concerned, the way is clear for possum control by 1080. [Chapter Break] Although a kaka recovery programme as inaugurated in 1996, it will be at least three to four years before results are seen, because of infrequent kaka breeding. Even on pest-free, offshore islands, a good breeding season occurs only once every two to four years. In the first year, $250,000 was budgeted for the programme, and Terry Greene says most of this money was directed towards research. "Until we have answers to some critical questions, we won't know how to direct further money into management." Keeping populations of kaka on islands is regarded as an insurance policy in case kaka become extinct on the mainland. However, islands like Kapiti are not pristine environments, and even on islands the breeding success of kaka is cause for concern. "We can't afford to do nothing about kaka on the mainland and just rely on island birds to prevent extinction of the species," says Greene. "Kaka are an integral part of our mainland forests—without them they would be much poorer places." The forests are already in a parlous state, and it will be a long time before kaka are able to lose the suspicious nature necessary for survival on the mainland. Only with money, management and perhaps a miracle will kaka again reign in our treetops.
Thanks, you're good to go!
Thanks, you're good to go!
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