10 climate change canaries
1 The Argentine ant It's been called the "Ghenghis Khan" of the ant world, and for good reason. The notoriously invasive Argentine ant has a global track record of devastating and altering the biodiversity of native communities it enters. But, by watching shifts in its distribution around the country, we might find some use in it as a handy indicator of change. Like other insects, this ant is substantially affected by temperature, and to successfully reproduce and maintain a foothold in any environment, it needs a minimum number of "heat units", which scientists call degree days. Presently, this pest is limited by temperature around New Zealand, and work by scientists has found they can survive and reproduce just fine, especially in the northern areas. But climate change's impact on rainfall and humidity may likely bring populations to currently unoccupied areas such as Wairarapa, Canterbury and Marlborough. "Argentine ants are found in isolated pockets of these locations already," Victoria University ecologist Professor Phil Lester said. "But our climate models predict them to become more widespread, abundant and persistent in such areas." Increased temperatures may also allow the ants to persist in high-value conservation areas - and it's these places that we most want to exclude them. As well as being infamous as a voracious predator and a farmer of scale or aphid insect populations, the ants also act as tiny reservoirs for pathogens and disease - among them deformed wing virus, a scourge among honey bees. "If our models are correct and the distribution and abundance of Argentine ants increases with climate change, so may the distribution and abundance of such pathogens." 2 Kauri Kauri remain the longest-lived and largest of New Zealand's tree species, and to last for 1500 years or more, they obviously need to be resilient. Yet, by measuring their year to year growth rates, we've been able to discover that these forest giants are responsive to climate fluctutations. These environmental changes can be measured in the size of the trees' annual rings, and researchers have found this pattern correlates well with the El Nino Southern Oscillation, or ENSO, cycle. Over the past four years, Auckland University biologist Dr Cate McInnis-Ng and colleagues have been measuring kauri responses to climate and building up a dataset to better understand how the species responds to change. For plants generally, climate change could cause some plants shift into higher elevations as temperatures changed, or threaten their survival with increasingly severe and frequent droughts. Dr McInnis-Ng's work has shown that kauri have some water saving mechanisms such as deep roots and large internal water stores - but there have been some anecdotal reports of kauri death in Northland during the 2013 drought that are unrelated to dieback disease. "Water reductions can also change other plant functions and we measured a distinct impact on the carbon cycle during the 2013 drought," she said. "Kauri reduce their leaf area during drought, as a water saving mechanism, and this means there was a big increase in inputs of carbon and other nutrients to the forest floor during the drought. "We are continuing monitoring to understand what this means for carbon storage and reproductive output in subsequent years. "This finding tells us that we may need to revisit our models of carbon uptake and storage in forests under future climates." 3 The humpback whale One of the key ways scientists can gauge how these gentle giants will respond to climate change is checking for any shifts in the time they leave from their Antarctic summer feeding grounds. While we don't yet know the exact cues whales use to start their migration north, changes underway in Antarctica will give away if they're linked to food or temperature. Auckland University marine biologist Dr Rochelle Constantine said there was already concern about changes in habitat use and body condition of humpback whales, which were indicative of changes in prey productivity. For five months of the year, the whales in Antarctic waters primarily feed on krill, which feed on phytoplankton found under the sea ice. When the sea ice melts in summer, the phytoplankton are released and reproduce rapidly with the increasing daylight hours. "Changes in sea ice production means a change in phytoplankton production and ultimately, at least in some areas, a decrease in krill and that means less food for whales," Dr Constantine said. "This is a complex system in a remote place, but we are working towards understanding what these changes will mean." Most concerning was that if the whales' prey became compromised, they wouldn't find enough food to get them through their later 4000km migration runs to tropical waters. This month, Dr Constantine and her team are putting tags on humpback whales passing Raoul Island to understand where they go to in Antarctica and what they are feeding on. "That way, we can see how New Zealand's humpback whales might be affected by changes in the ice conditions and subsequent productivity." 4 Deep corals Our waters are home to an abundance and colourful diversity of deep sea corals, but we're only beginning to understand how they might respond to climate change. While measures like the temperature, acidity and carbonate content of sea water is already telling us climate change is transforming our oceans, gauging the effect this is having on our unique coral communities isn't as simple. This is because there are many processes that can naturally change the abundance and distribution of marine organisms, and the slow-moving effects of climate change makes it especially to differentiate impacts from "normal" variability. However, scientists could use climate models to predict what the temperature and acidity of the ocean would be in the future if the climate continued to change at its current rate, and then mimic these in controlled experiments to observe changes in weight and growth of coral. "At this stage of our research, we don't really know how resilient the corals are to change and whether there are thresholds or tipping points beyond which they cannot recover," NIWA deepwater scientist Di Tracey said. We do know, however, that corals are very sensitive to multiple potential "stressors", namely the combination of temperature change and ocean acidification. The changes would be long-term, but in deeper, stable waters, where even small environmental change in the ocean climate is significant, we may see faster changes, Dr Tracey said. Corals thrive when waters around them saturated in two carbonate chemicals - aragonite and calcite - but ocean acidification reduces the amount of aragonite and calcite in seawater. Corals, along with many other marine species, use these chemicals to grow their skeletons. "The models that are used to predict future climate change for the IPCC all indicate that the areas where these carbonates are saturated will shrink dramatically by 2100 due to ocean acidification if we continue on our current path." 5 Tuatara As reptiles, the tuatara is very responsive to temperature - when it's cool, they're relatively inactive, and may not eat for the winter months in cooler climates. Further, they're likely to be more inactive during dry periods, hiding in their burrows and conserving water. Hence, said Victoria University researcher Dr Nicola Nelson, warm, dry climates may result in limitations for populations and reduce survival of vulnerable hatchlings. A compounding factor was that nest temperatures themselves can influence the outcome of hatchlings - and as warm nests tend to produce males, the trend may shift sex ratios if the females fail to respond and shift their nest sites. Add to that the impact of climate change on their isolated habitats. "They live largely on small islands, which are likely to experience loss of land through sea level rise and erosion from rogue weather events predicted to become more frequent in future." 6 Sooty shearwater When it comes to long-haul trips to other side of the globe, the sooty shearwater is a frequent flyer. While around our part of the world, it feeds in southern polar seas, before beginning its annual migration from New Zealand all the way up to the Arctic. It's these epic journeys that makes it a useful indicator for what's happening to the planet. For example, last year, when the Bering Sea was 3C warmer, Department of Conservation staff noticed a higher mortality rate among the birds that had just made the journey back to New Zealand. Migrating seabirds in general are reliant on a high quality diet to put on sufficient fat - up to 50 per cent of their body weight - in order to make their migration. Further, they have to feed a chick weighing up to 120 per cent of their own body weight, and this makes them and their offspring vulnerable to any environmental changes that affect the availability or quality of prey. Is climate change already starting to have an impact? "In the absence of ongoing monitoring programmes in New Zealand, it's hard to say," Auckland University biological sciences lecturer Dr Brendon Dunphy said. "But in other species, we are seeing shifts in when breeding starts - earlier than usual - and movement of colony locations towards the poles." 7 The native bee Could our native bees prove buzzy little cage canaries for the earliest signs of change? New Zealand can boast more than 20 species of native bee, many of which have different times of the spring and summer when their young emerge. There's a suggestion that this differing timing is linked to key flowering plants they rely on, with both the bees and the flowers timing their behaviours based on environmental cues. For plants about to flower, these cues are typically the length of days and the overall accumulation of temperature over time. "So climate change has some potentially interesting effects - temperatures and weather conditions will change, but daylength won't," Plant and Food Research scientist Dr David Pattemore said. "One concern is that there could be increasing mismatch between the timing of flowering and the timing of emergence of the pollinators that need the plant and that the plant needs." Dr Pattemore believed no-one yet would have recorded any of these potential issues in New Zealand, partly because there were few people who could study native bees, and that their natural ecosystem had been filled with exotic plants and exotic pollinators like honey bees and bumble bees. "So with all these extra flowers and pollinators, the mismatch in timing between native bees and their native plants might be harder to discern," he said. "However, this system could be a really useful measure of the effect of climate change on natural ecosystems if we can understand how the phenology, or timing, of native bees is linked to the phenology of native flowers." 8 The rockhopper penguin These quirky-looking penguins many of us know from the animated hit movie Surf's Up are among the first species on the planet to pick up the wider effects of climate change. One of its habitats is the subantarctic Campbell Island, around 700km south of the South Island and in the area of the globe known as the "furious fifties", where there's been growing efforts by climate scientists to search for cues and clues in an area particularly sensitive to global change. Between the 1980s and 2012, the penguin population has declined overall by 22 per cent, with scientists linking the drop and occasional recoveries to changes in sea surface temperature. Particularly, warm periods bring lower food availability and drive population declines, while cooler periods help recoveries. "Hence, we have a more or less resident seabird species which has shown dramatic population fluctuations which appear associated with changes in sea surface temperature, and which may be further linked to changes in prey availability," NIWA seabird ecologist Dr David Thompson said. He said it may well be that the penguin is affected by prey availability at specific times of the year, or in phases of the breeding cycle. "For example, when breeding is complete and chicks have fledged, rockhopper penguins depart to sea to feed ahead of a complete annual moult. "Acquiring sufficient food resources during this post-breeding feeding stage is crucial because birds then return to Campbell Island to moult and cannot feed until a new set of feathers has been grown. "Simply, if a bird has insufficient reserves acquired from the post-breeding period it will starve before being able to get back to sea to feed again." Ultimately, monitoring changes in the Campbell Island population would reflect changes in the general marine system, he said. "Building on work already undertaken might reveal more subtle responses that would help explain how and why changes in the overall population occur." 9 Sea squirt One of the biggest winners of climate change could be the sea squirt - a slimy filter feeder that, despite its innocuous appearance, is among our marine environment's most prolific and harmful pest species. As climate change proceeds, it's predicted that aquatic systems may be particularly vulnerable to invasion from such ocean scourges, and sea squirts seem to have superior abilities to colonise, compete and resist predators. Cawthron Institute scientist Dr Kirsty Smith said these advantages would only be boosted as temperatures increased. "Invasive sea squirts also have characteristics that assist with adaptation to environmental change as they have already survived new stressors and environments during their transportation." Studies have shown that increased seawater temperatures have already resulted in changes to the marine environment that favours invasive over native species. Dr Smith said increasing levels of invasive sea squirts would influence the way the ecosystem functioned, and bring economic impacts with changes in water clarity, native species abundances and diversity, and competition with farmed shellfish. Cawthron scientists are now using a highly invasive sea squirt, Didemnum vexillum, to investigate if environmental stress can cause changes to the expression of sea squirts' genes without any effects on its DNA sequences. "This work will increase our knowledge of how marine organisms can rapidly adapt to climate change and avoid widespread extinctions of local populations or even entire species." 10 The mouse Because of their tiny place in a complex natural system, mice aren't considered an ideal sentinel species for climate change. But a warmer world will likely have indirect effects - and largely beneficial ones - for this widespread rodent and enemy of many of our native species. These changes will potentially provide mice a better food supply and a more suitable habitat for them to live in. There was some evidence, Landcare Research scientist Dr Andrea Byrom said, that warmer climates in the eastern South Island will result in more shrubland vegetation in the high country, affording mice refuge from predators like stoats and a ready supply of seeds and fruits to nibble on. One major boost to their food supply will come with large seeding events, or "masts", in beech forest and tussock grasslands that today happen every four to six years - but could happen as frequently as every two to three years under climate change. During these events, mouse numbers increase dramatically, and they eat many species of native fauna such as birds' eggs, weta, and other invertebrates. They in turn also provide a food supply for other invasive predators such as stoats. This causes a problem for conservation managers, who will have to plan and budget for large-scale pest control activities, as the Department of Conservation did last year with its $21 million "Battle for Our Birds" campaign. What might happen in the future with mast events under climate change, and potential outbreaks of mice, is being investigated in a joint project between NIWA and Landcare Research, said Dr Byrom, who is also serving as director of the Biological Heritage National Science Challenge. "There is some evidence of increased frequency of mast seeding in beech trees in the Orongorongo Valley near Wellington, and direct evidence that mouse outbreaks occur more frequently as a result." Under present projections, the mean temperature in New Zealand could be 2C higher by the end of the century - and even between 3C and 4C higher if no action is taken to curb carbon emissions. Within the same period, sea level is expected to rise between 50cm and 100cm, leaving populations to adapt by either abandoning coasts and islands, changing infrastructure and coastal zones, or protecting areas with barriers or dykes. A recent report on sea level rise by Parliamentary Commissioner for the Environment Dr Jan Wright said the impact of even a small rise in sea level would be significant and costly for some landowners. Large storms occurring on top of a higher sea level - of which an increased number were predicted - would affect public infrastructure such as roads, railways and stormwater systems, as well as private homes. Horticulture production in some regions may become uneconomic due to a lack of winter chilling, while sub-tropical crops such as avocados and citrus may benefit from warmer conditions. Rising ocean temperatures and ocean acidification may alter marine life, moving fisheries southward, threatening shell fisheries and changing life cycles. New Zealand is taking a new target of reducing its greenhouse gas emissions by 30 per cent from 2005 levels and 11 per cent from 1990 levels by 2030 to December's UN crucial climate talks in Paris. The incidents are being investigated and firefighters may face disciplinary action.