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| The sea cliffs on beautiful Christmas Island. But will islanders have enough freshwater within coming decades? Photo: Inger Vandyke |
Islanders are in for a tough time. As if rising sea levels were not enough to contend with, about 16 million people living on three-quarters of the world's small islands face seriously dwindling supplies of freshwater as a consequence of climate change.
Australia's Cocos Island and Christmas Island, along with New Zealand's Cook Islands, are among the 73 per cent of 80 sampled islands which, by the year 2050, will put islanders at risk of reduced or no freshwater access, US researchers have reported.
Previous climate models have had trouble assessing the sort of very small islands found in places such as French Polynesia or the Marshall Islands. Researchers, led by Kristopher Karnauskas and colleagues of Boulder Colorado University, overcame this by estimating the water loss from evaporation through plant leaves or from surfaces.
"We found that about half of the island groups will experience
increased rainfall, mostly those in the deep tropics," Dr Karnauskas
said. "Increases in evaporation were more consistent across the islands,
resulting in a shift of global island fresh water balance towards
greater aridity."
The research, published in the journal Nature Climate Change,
reveals that, while half the islands, mostly in the deep tropics, will
experience increased rainfall, the other half will experience increased
evaporation, drying them out."There will be vegetation changes due to the reduction in freshwater availability," said Sydney University hydrologist Willem Vervoort. "There will also be changes in the opportunities to produce fresh food and vegetables on the islands using natural freshwater."
So the islands will become more arid, with reduced tree cover and increased heat stress, Associate Professor Vervoort said.
For most islanders, the cost of water will soar. "Either water needs to be imported or desalination needs to be increased," Associate Professor Vervoort explained. "Alternatively, there needs to be investment to capture and store more of the rainfall that will occur and increased water recycling, including from treated sewage."
Other effects include a loss of water quality and the raised risk of algal blooms.
"Due to high tropical rainfall, we have so far not faced freshwater shortages on Christmas Island," said long-time resident Sharon Tisdale. "Contamination of the water table due to waste disposed in landfill is of particular concern to us."
Ms Tisdale said that strict monitoring was required to ensure that toxic substances are not dumped.
"The council has just implemented disposal charges for tyres and batteries," she explained. "This will mean they will be dumped where there is no charge, in the jungle or on the side of the road, which is already happening."
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