Our most vulnerable creatures
As the planet warms, we can monitor these species as climate change’s coal mine canaries, writes Jamie Morton
New Zealand’s species have endured sweeping transformations brought about by humans and the pests we’ve introduced.
Scientists say predicting what will happen with several degrees of temperature rise and other impacts of climate change, ranging from rising seas to wilder weather, is tough.
That’s partly because our climate is already variable and partly because there’s uncertainty about flow-on effects that could make the picture even worse.
But we do know that all of our native species and their ecosystems will be affected somehow.
Alpine environments — refuges for many birds, lizards and invertebrates — will be among the first to suffer as our climate warms.
In our rivers, streams and lakes, freshwater plants and animals will experience more intense floods and droughts and the knock-on impacts of more irrigation and new pests and weeds.
On our coasts, estuaries and islands, rising seas will squeeze already fragile habitats against developed land.
Scientists say some species — among them, tuatara, takahe, rockhopper penguins, little spotted kiwi and Archey’s frog — have bleaker prospects for adaptation than others.
Scientists also tell us we can turn to such species, along with others that aren’t so welcome in our wilderness, for some of the first cues of climate change. Weekend Herald has taken a look at five of these coalmine canaries — or sentinels of change, as researchers dub them.
The little blue penguin
The world’s smallest penguin can typically be found in areas that offer sanctuary from mammalian predators.
Because they breed on land but feed in the sea, penguins, like many seabirds, will be doubly affected by climate change as there will be no refuge.
Increases in seawater temperature will have dramatic impacts on the distribution of prey such as fish, squid and crustaceans, meaning adult birds may have to work harder to provide chicks with enough energy.
This may lead to weakening chicks and increasing starvation.
And if temperatures within burrows climbs higher than 35C, it would be “highly problematic” for the species, University of Auckland Biological Sciences lecturer Dr Brendon Dunphy says.
“Birds cannot sweat, thus hyperventilation to increase evaporative cooling is necessary.”
Because this is a big energydrainer, it could prove fatal for adult birds and conservation rangers may have to intervene with artificial nesting boxes.
More intense storms will have an impact: the penguins, which typically forage within 20km of their nests, might struggle to find prey in waters made murky by churned-up sediment.
“But given that they are accessible on land, we can more readily monitor colonies,” Dunphy said.
“Their health is a summation of atsea conditions — thus any decrease in colony or individual health represents a signal of change.
“Our job is to now decipher what exactly this is, and construct appropriate responses.”
Rats and mice
The rodents that plague New Zealand’s wilderness, killing millions of native birds each year, are already responding to climate change.
Last year’s spring and summer brought just the kind of hotter, wetter weather we could expect from climate change.
Under these conditions, rats in the North Island were starting to behave more like they did on tropical islands — with longer breeding seasons and bigger populations.
“This creates problems for our breeding native birds over summer, and when hungry rats come into people’s houses in autumn, potentially bringing diseases with them,” University of Auckland ecologist Dr James Russell explains.
In the South Island, invasive mice were climbing to higher altitudes, pushing above the treeline into alpine areas.
There, they threatened endangered native species such as rock wrens, lizards, and invertebrates.
Whereas pest control could effectively manage rats and stoats in these areas, more work was needed to develop landscape control tools for mice, which Russell said weren’t just “small rats”.
Bryde’s whale
Bryde’s whales, unlike most baleen whales that migrate seasonally, are year-round residents in the Hauraki Gulf and northeastern waters.
These 15m-long whales have a diet
of small, schooling fish and zooplankton and forage almost entirely during the day, stopping to rest at night.
As they need to get all their daily energy requirements from this region, they are particularly responsive to prey movements and anything that might influence their prey.
With seasonal and spatial differences in where they find their preferred prey, we typically see subtle seasonal shifts in their distribution.
The 2015-2016 La Nina event and 2018 oceanic “warm blob” saw a major shift in whale distribution to the outer regions of the gulf, as sea surface temperatures up to 3C above average made it too warm for plankton.
“With plankton at the beginning of the food chain, if they move, then the rest of the food chain, which is highly dependent upon them, may also move,” says Associate Professor Rochelle Constantine, a marine biologist at the University of Auckland.
Though the whales used to forage more on fish, zooplankton were their primary prey now.
“The reason for this shift is unknown but may be related to changes in habitat, disease events or fishing,” Constantine says.
“We are working to understand the drivers behind distribution of all the megafauna, including the whales, but these last few years have shown that for whales, which can easily move across large spaces, they will go where their food goes.”
It is possible the whales have moved to ensure they don’t overheat — yet they have been observed in tropical waters and have a thin blubber layer, so are well suited to warmtemperate waters.
“For now we think movements are most likely related to prey availability and as our oceans warm, our future might see no Bryde’s in our inner gulf waters.”
Cobble and chesterfield skinks
The cobble skink has just been discovered, yet climate change and other pressures could soon see it gone. It was found in 2007 in its only known habitat, a tiny beach north of Westport.
As its name suggests, it prefers the deep, cobble habitat found immediately above the high tide mark and appears to have adapted to wriggling through the spaces between cobbles.
It’s likely this habitat has kept it from introduced predators like mice, rats and cats.
Yet only a decade since its discovery, its population has declined significantly with coastal erosion — its habitat is now limited to one hectare.
Severe storms and rising seas that would come with climate change would only worsen the situation.
Things are just as dire for another recently discovered skink species, the chesterfield skink. Though it’s possible these creatures once lived in trees, they have been pushed out of rough pastoral areas and into a thin strip of coastal habitat, where they face the same predicament as the cobble skink.
Department of Conservation scientists are urgently trying to better understand the causes of their decline and develop recovery strategies.
Snow tussock
It helps control erosion, influences water yields and supports a host of other species. But the snow tussock that blankets much of the South Island’s high country depends on weather cues to time its flowering events every few years.
This appears to be in sync with southern beech forests — and a big masting season typically occurs when the previous summer has been much warmer than the one before that.
“So, clearly, changing weather patterns can have big effects on how often there are large tussock flowering years,” University of Canterbury ecologist Professor Dave Kelly explains.
“If climate becomes gradually warmer over decades, they won’t be too badly affected.
“But if climate swings more wildly from hot to cold and back, there will be more frequent mast years.”
Unfortunately, this already appears to be happening. Snow tussocks rely on masting to make life hard for their seed predator insects. If the tussocks mast more often, the insects might increase in numbers and eat more of the seeds.
“So tussocks would end up with fewer viable seeds produced,” Kelly said.
“This will happen just as snow tussocks really need to be making more seeds so they can migrate, or disperse seeds, up-slope to cooler habitats as the planet warms up.”
Further, big snow tussock seed crops seem to drive increases in mice — and therefore stoats — in alpine regions, which poses a direct threat to high altitude animals such as takahe and rock wrens.
Lastly, repeated heavy flowering could take a toll on the tussocks.
These plants seem to be immortal — they have lived for centuries in their natural alpine habitat, as long as they aren’t burned and overgrazed.
But some plants that Kelly and his colleagues have transplanted to warmer, lower altitudes, have become visibly affected after just a few years.
“Some have died completely, presumably because they have been putting so much effort into reproduction and not enough into producing new leaves and shoots,” Kelly says.
“So snow tussocks are tied to air temperatures, and year-to-year fluctuation in temperatures, much more tightly than many species are.
“They seem to be already feeling the impacts of a warmer climate . . .
“All of that makes them one to watch as we slowly push temperatures higher.”
As our oceans warm, our future might see no Bryde’s in our inner gulf waters.
Rochelle Constantine, University of Auckland.