Just back from the Pacific
- 2 Oct 06, 08:57 AM
The Pacific is a vast ocean peppered with island nation states. Both the sea and the coral islands are home to brilliant wildlife - And on this many peoples depend. But the corals can fight back - But can species such as turtles? Turtles have a profoundly important ecological role in the shallow seas and their conspicuous plight due to climate change can only further weaken the coral reefs on which so many species and people depend.
We put Gabrielle in the water with top coral expert from the University of the South Pacific Leon Zann. Beatrice canoed along side with all the recording gear to collect a brilliant interview seeing at first hand the effects of global warming on coral reefs, and the awe and wonder of these places so rich in life. We were snorkelling off a small island in Fiji and saw plenty of evidence of coral bleaching. This is actually the tail end of the winter in Fiji - when the sea is at its coldest - so seeing bleaching, which is an event directly related to high sea temperatures, was surprising in a way. And at last we have a really good explanation of what bleaching is. Bleaching is a stress response of the individual coral animals (small anemone like polyps). Each coral polyp has a symbiotic plant living amongst its tissues which provide food for the coral. The algal plant gets protection in return. When the sea temperatures get too high the corals eject their passenger. These single celled plants can free swim and so they do in the ocean. The coral doesn't die and if the heat stress goes away the alga can swim back into the polyp. If the temperatures remain high for weeks, then the corals will die - they die from starvation. We've just heard that there's a massive coral bleaching event going on around Madagascar.
PACIFIC ISLANDERS DEPEND ON THE CORAL REEFS
In the South Pacific there are a number of island nations. Fiji, The Solomon Islands, Kiribati, Tuvalu, Tonga and Samoa are some. Around all these islands have fringing coral reefs. A fringing reef extends from the shore as a plateau and extends to where it gets deeper and it's here a fringing reef grows. Beyond is the open ocean, descending k's of metres. Both the plateau and the reef fringe are packed with molluscs and crustaceans and fish and 75% of the South Pacific islanders depend on the health of this local larder. In addition, the fringing reef protects the coastal region from storm surge and allows the all important mangrove habitat to develop in the shore margins - again, another natural protector of the coast (mangrove stabilises mud). Rising sea levels and coral bleaching threaten to unseat the reef. We saw plenty of evidence of coastal damage, salt water incursion onto land and wrecked mangrove swamp.
THE REEF CAN FIGHT BACK
Leon Zann tells us that sea levels have gone up and down over time as have sea temperatures. Coral reefs are ancient wildernesses and have moved here and there with the sea many times. When driving in the interior of Fiji, we saw tall mountains with fossilised coral reefs all the way up the slopes - evidence that the sea was much higher millions of years ago.
Within a reef are a myriad of coral species, and just likes trees in a forest, they jostle for space and access to light. Some are big, some are small. Others fast growing, others slow. All this variety makes the reef inherently able to respond to change. So what's the problem? Some people believe that left to their own devices the coral reefs will shift to where ever the water is the right depth and temperature. The problem occurs with the development of islands for people to live. Where coastal development is high, there's little or no where for the corals to shift. Also, many believe the temperature events happening right now are bleaching corals on an unprecedented scale - 1998, 2000 and 2002 were all huge bleaching events. Most reefs recovered, but not so around the Maldives in the Indian Ocean. 95% of the corals died in the Maldives, compared to 5% on the Great Barrier Reef off Australia. If the Maldives were replicated on all reefs there would be a catastrophic loss of global biodiversity.
THE PLIGHT OF THE CORAL ATOLL NATIONS
Kiribati and Tuvalu are nations founded on coral atolls. These atolls are basically the tips of huge submarine mountains that have been colonised by corals. Weather and the industrious actions of coral busting fish have turned old coral into white sand - And hence a paradise island is born. Storms continually break the coral and toss it into the centre building the island. You could argue that increased storm events will only make coral atolls larger. I'm told by experts that's basically true. Storms are part of the genesis and maintenance of the island. The problem comes when people live on them. Tuvalu has about 20,000 people across its islands, the Kiribati about 60,000. Both islands soar to a meagre 3m above sea level. Sea levels have risen 13cm since 1841 and this is having profound effects on storm surge damage of property and salt water incursion into their drinking water (every atoll has a fresh water cell beneath it). These two nation states live with the reality that as a nation they might have to evacuate. The people of these nations blame those in the developed world for global warming and the imposing threat to their homeland. A message very similar to drought ridden parts of Africa.
We interviewed WWF South Pacific people and learnt that various turtle species were in dire straits. A bizarre fact of life is temperature determines the sex of turtles. 1 degree hotter can make males females. One degree colder, the other way. We are told that a shift in the sex ratio is already being observed - hotter beach temperatures generating more females, and where there's excessive resort development the shade on the beach actually does the reverse. We're told by people at the University of the South Pacific and by WWF South Pacific that the survival status of turtles in the region is more critical than that of coral reefs. Changes to their breeding beaches and shifts in ocean currents are having a major toll. The turtles perform vital roles maintaining the diversity of the reef and their loss could have huge consequences for the reef and people in the region.