The biology of our far south – the southern ocean, the sub-Antarctic islands, and that slice of Antarctica known as the Ross Protectorate – is changing.
On our sub-Antarctic islands, populations of rockhopper penguins are down by 94 per cent, southern elephant seals down by 97 per cent, and there’s been an 85 per cent reduction in grey-headed mollymawks (a type of albatross) – all since the 1940s.
Though we can see more species slipping towards extinction, it is more difficult to point the finger at what is causing the problem. Ecosystems can usually handle one, or even two shocks, but there’s a limit. If a species is lost, we often can’t say what caused it. Was it climate change, acidification, or fishing? Often we simply don’t know.
The answers can be subtly different for different species.
Rockhoppers are the bushy-blond eye-browed penguins resident on our own Campbell Island. Niwa scientists have studied their decline, and the reason seems to be changes in the quantity of their food supply. What is driving this?
Climate change is the chief suspect – as the Southern Ocean warms, the currents that determine how much life is generated in the sea change as well.
Some seabirds, on the other hand, have been impacted by the race for resources, particularly fishing. Between the 1960s and 1980s fishing in the Southern Ocean increased dramatically, and many of these birds were lured to their death by the thousands of hooks baited with squid behind long liners, or by the offal cast out by trawlers.
Over time, standards have improved and the death of seabirds has been lowered. The challenge is to keep improving and press for best fishing practice around the world, because we know these birds can cover huge distances. They’re catching our birds over there.
Some of the more tightly regulated and monitored fisheries around Antarctica have shown what is possible, by reducing birth deaths to almost zero.
The situation with elephant seals could include all these sources of trouble, and possibly others. Some think that after the whaling boom, elephant seal populations grew to supplant the place of whales in the ecosystem, so the population may have “overshot” the food supply. Similarly, killer whales and sharks, with a reduced number of sea mammals to eat, may have turned on elephant seals to meet their need for 200kg of meat a day.
The point is that almost completely removing the great whales from the Southern Ocean ecosystem has had huge knock-on effects which we will probably never understand. We have no idea what is a “natural state” in our far south.
Rising temperatures will probably hit true Antarctic species the hardest because they are adapted to the extreme cold and the “boom and bust” annual cycle of the ecosystem. During the summer, constant sunlight and melting ice provides a plankton bloom – a feast followed by nine months of relative famine. As conditions change, and the “summer” is prolonged, true Antarctic species will be shunted along by their sub-Antarctic cousins, who have adapted to the warmer conditions.
We are already seeing this as the sea ice melts around the Antarctic Peninsula. Colonies of the resident Adelie penguin are down to one third of 1980 levels. And as the Adelie disappears it is being replaced by gentoo and chinstrap penguins, which are colonising the area from the warmer sub-Antarctic. These incoming species are used to finding their food in open waters, so aren’t dependent on the sea ice or the huge bloom of life that comes when the sea ice melts.
If this is a sign of the future then the days of the Adelie, and even the majestic Emperor penguin (our mate Happy Feet), could well be numbered.
But who cares? Is this loss of biodiversity really a problem? Species come and go, and should we worry if some get pushed out when conditions change? Rates of extinctions are already up to 1000 times the fossil record and this is projected to increase by afurther factor of 10 soon. As far as nature is concerned, the rise of humankind could end up as the equivalent of a meteor hitting the earth.
Why does biodiversity matter? We can’t profess to understand the complexities of nature, but there does seem to be some benefit from diversity. This is known as the portfolio effect – a phrase that appeals to an investment fund manager.
The idea is the same as investing money – don’t put all your eggs in one basket (unless you know something everyone else doesn’t). In nature’s terms, this means an ecosystem with more species is far more robust and able to endure and recover after something bad happens. Monocultures don’t do that. Find the right disease and it all gets wiped out in one hit.
Perhaps an even greater concern is that climate change could be altering the way the Southern Ocean functions. The currents, winds and freeze/thaw cycle of sea ice in that area determine how the ocean mixes, all of which can affect the amount of life that the ocean can sustain. Climate change will almost certainly lead to different life existing in different places, although the jury is out on whether it means more or less life in the ocean overall.
The human race for resources such as fishing, territory and minerals is only some of the cause of the changes in the biology of our far south. However, it is that race over which New Zealanders have the most direct control over, particularly in our own territory. We all know how hard it is to turn back the human drivers of climate change, but much can be done to manage any side effects of the race for resources and to mitigate the damage on key species and the environment.
The most extreme strategy to protect biodiversity is to close certain areas to resource extraction by establishing no-take reserves.
The international community has already effectively done this with the Antarctic continent itself, and our sub-Antarctic islands also have World Heritage status. Currently the debate is over protecting the Ross Sea. Most people agree this sea is special, although there is a healthy debate about just how much protection is warranted.
In some cases we’re going even further by repairing the damage from our past actions. Pest eradication on Campbell Island was the biggest undertaking of its kind in the world to date. Now the natural habitat is regenerating, and hopefully this will provide more breeding space for our seabird populations. The question now facing New Zealand is whether to spend the $20 million needed to eradicate pigs and cats from the 50,990 hectare Auckland Island.
All these issues and more will be debated during our voyage south next month with 40 everyday Kiwis and 10 of our best scientists. The objective is to raise our awareness of the area, its importance to us and the threats it faces.
You can follow us on www.ourfarsouth.org. We look forward to sharing what we find as the science, geopolitical, and economic experts tussle over what’s realistic and what isn’t.
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