ELF – Engelsk läsförståelse (HPHÖST2021P2)

Rising Seas

Rising seas are eating away at small islands and will eventually turn their inhabitants into climate refugees, right? Not so for some of the world’s most threatened islands, which have grown despite experiencing dramatic sea level rise.

Funafuti atoll, which includes the capital of Tuvalu, is an islet archipelago in the tropical Pacific Ocean made from coral debris washed up from an underlying reef by waves, winds and currents. Over the past 60 years, the sea has risen by around 30 centimetres locally, sparking warnings that the atoll is set to disappear.

But Paul Kench of the University of Auckland, New Zealand, and colleagues found no evidence of heightened erosion. After poring over more than a century’s worth of data, including old maps and aerial and satellite imagery, they conclude that 18 out of 29 islands have actually grown. As a whole, the group grew by more than 18 hectares, while many islands changed shape or shifted sideways.

“There is still considerable speculation that islands will disappear as sea level rises,” says Kench. “Our data indicate that the future of islands is significantly different.”

Storms and other disturbances that churn up the sea seem to be more important than sea level in influencing stability, according to Kench. Storms break up coral, which then gets deposited on the atolls. He says other coral reef islands are likely to evolve in the same way, and that the Maldives seem to be showing a similar effect.

“There is presently no evidence that these islands are going to sink,” says Virginie Duvat of the University of La Rochelle in France. She says that she and other researchers are trying to fight the widespread misconception that sea level rise will mean the end for atolls. However, Kench’s findings do not apply to other types of islands, like the volcanic main islands of Fiji, Tonga and Samoa.

If atolls are not sinking, could people continue to live there? “Where shoreline changes are rapid, islanders have already had, in some cases, to move to more stable places,” says Duvat. Rural inhabitants commonly adapt in this way as their houses lack permanent foundations, she says. “The lifetime of such houses is short, allowing people to relocate quite easily.” But it would be harder for urban residents to adapt, says Duvat.

And climate change could result in bigger, more frequent storms. These could be catastrophic in the short term even if they increase the area of atolls in the long term, says Tom Spencer from the University of Cambridge. “The challenge for island nations is to figure how they will coexist with their changing islands,” says Kench.

Team member Roger McLean of the University of New South Wales in Sydney, Australia, who is also a coordinating lead author on the small islands chapter in the latest Intergovernmental Panel on Climate Change (IPCC) report, says Kench’s findings are important because of the time frame. The sea level change at Funafuti over the past century is similar to what the IPCC is projecting for the year 2100.

“There will be less emphasis on external migration of ‘environmental refugees’ from atoll nations that has gained such prominence in the last few years,” he says. But he notes that the atoll-building sediment comes from productive coral reefs, which face a range of threats such as warming oceans and pollution.

Penny Sarchet, New Scientist

Pest Management

Cassava’s starchy roots are a staple for millions of Africans, but cassava mealybugs, accidentally brought to Africa in planting materials from South America, ravaged the continent’s crops in the 1970s and 1980s, decreasing yields by up to 80 percent. Scientists found a solution in natural pest management, implemented by growing numbers of farmers worldwide by means of biopesticides and biological control agents, including natural materials such as plants, bacteria and fungi. Predatory and parasitic insects are a form of biological control. All these methods work to keep pest levels low enough to minimize crop losses without posing a major threat to the environment.

Demand for produce free of pesticide residues is driving the increase in biopesticides, which are inherently less harmful to humans and break down more quickly than typical agrochemicals. Some beneficial fungi even go beyond pest killing by liberating soil nutrients that promote plant growth.