Climate Wire | Just a year ago, invasive rats were crawling on the tiny island of Iluigi in the Marshall Islands. For decades, starving rodents have been rampaging there, devouring the eggs of native seabirds and threatening local biodiversity.
But as of March, the tiny island was declared rat-free. This is thanks to his year-long campaign to eradicate rodents and restore the island to its natural state.
The effort is being carried out by the Department of Natural Resources and Commerce of the Republic of the Marshall Islands with the support of the Pacific Regional Environment Program Office (an intergovernmental organization focused on climate and environmental issues in the small islands of the Pacific) and a non-profit island organization. Did. Conservation activities that work to remove invasive species from islands around the world.
“The island feels alive again,” said Kennedy Kaneko, the Marshall Islands National Invasive Species Coordinator, in a statement. We found plenty of seabirds and crabs.”
Iluj is just one of several small islands in the long volcanic and coral atolls that make up the Marshall Islands, which dot the central Pacific Ocean between Hawaii and the Philippines. Still, there have been small successes in a series of global efforts to eradicate invasive species, especially from small tropical islands.
Experts say such efforts could help protect fragile island ecosystems that are home to endangered and endangered species, including flora and fauna that may not exist anywhere else in the world. ing. It also helps strengthen the diverse coral reef ecosystems that surround many tropical islands.
And in the process, we can promote resilience to climate change.
Both small islands and coral reefs face existential threats from climate change impacts such as rising sea levels, warmer waters and ocean acidification. Curbing greenhouse gas emissions and halting climate change is the only way to truly stop these threats. But removing extra stressors, such as harmful invasive species, from the environment can make ecosystems healthier, more resilient, and more able to withstand the pressures of global warming.
Chad Hanson, vice president of conservation for the nonprofit Island Conservation, added that small islands around the world have historically contributed little to greenhouse gas emissions from a warming climate. However, they suffer disproportionate impacts from climate change.
“Your island communities are not contributing to climate change,” he said. “But it is they who are experiencing sea-level rise, they are the ones who are experiencing the presence of alien species that are more adaptable to rising temperatures and changes in soil chemistry, and they are It survives better than many of the exotic and landrace species.It is endemic.”
The Island Conservation is one of the leading organizations in tackling invasive species on the islands. The organization works on projects around the world, including South America, North America, the Pacific, the Indian Ocean and the Caribbean, with the goal of preventing the extinction of native species. It targets a variety of invasive species, including both plants and animals, but specializes in vertebrates such as mice.
Rats have traveled the world stowaways on ships for centuries. By one estimate, they have reached his 90% of the world’s islands, wreaking havoc in many of the places they invade. These have had a particularly devastating effect on the island’s seabird populations, many of which had few or no natural predators prior to their arrival.
“Rodents are generalists,” says Hanson. “So they can eat plants and feed on protein sources, which can directly attack birds, eggs, crabs, or native species that can be incredibly weak.”
It’s not just terrestrial life that suffers from rodent infestations. Nearby coral reefs are also at risk.
That’s because corals and seabirds are closely related. After feeding in the open sea, seabirds return to the islands to rest, breed and nest. While they are ashore, they deposit large amounts of guano (a fancy name for bird droppings) all over the island.
This guano is rich in useful nutrients such as nitrogen and phosphorus. Nutrients eventually flow from the islands into the water where they are utilized by corals and algae. Fish come and eat the algae, and nutrients move up the food chain. In this way, they help support the entire coral reef ecosystem.
But everything changes when rats take up residence.
“When you lose seabirds, you lose this trophic link,” says Casey Benquitt, a Lancaster University researcher who studies coral reefs and other marine ecosystems. “The amount of nutrients that the body can take in is greatly reduced.”
She added that it often causes problems such as fewer fish, slower fish growth and lower productivity in reef communities.
A recent study, published in January, demonstrated that rat-related seabird declines had unintended consequences. The study investigated locations around the Chagos Islands in the Indian Ocean and focused on small fish known as jewel damselfish.
They are typically aggressive and territorial species. They live around coral reefs and spend much of their time staking out patches of the algae they like to eat. Scientists call this “farming”. However, the study found that damselfish became less territorial when living around rat-infested islands.
There are fewer seabirds on these islands, and fewer nutrients flow into the water. As a result, the algae, which are favored by fish, become less nutritious. And that means fish aren’t worth spending their precious energy protecting tiny seagrass beds.
Rachel Gunn, a coral reef ecologist at the University of Tübingen in Germany and the lead author of the study, said, “The fish on the ‘crattled’ islands have to spend more time feeding to get the same amount of nutrients.” I have to,” he said.
On the other hand, eradicating invasive rats on islands can help restore nutrient balance and increase productivity in coral reef ecosystems. Benquit said research has shown that removing rats from the island could restore nutrient flows within about 15 years.
“You probably won’t get it right away,” she says. “But 15 years isn’t bad.”
In general, it’s good for the island’s ecosystem and native biodiversity. Hanson of Island Conservation noted that eradication campaigns can lift native species from the brink of extinction.
In one notable example, he said, island conservation helped eradicate invasive rats from the Galapagos islands of Rabida and Pinzon. After the mice were gone, a small gecko appeared in Rabida. This gecko is an animal that has not been recorded in the fossil record for 5,000 years.
“It was suppressed to a non-existent level,” Hanson said. But as the island recovered, so did the gecko.
Removing invasive organisms and restoring natural nutrient flow could also help islands and nearby reefs withstand the pressures of global warming and bounce back from climate-related disasters.
Coral bleaching is one example, says Benquitt. When corals are stressed (often due to ocean heatwaves), the colorful algae that live symbiotically inside the corals are expelled, turning white in the process. Bleaching does not necessarily kill all corals completely, and reefs are allowed enough time to recover once the source of stress is removed.
Benquit pointed out that there are some specific types of tough algae that help reefs recover. These help hold the reef together and provide a platform for new baby corals to settle and grow. And a 2019 paper found that islands with high numbers of seabirds tended to develop more of this algae after coral bleaching events than rat-infested islands.
“That might speed up recovery,” she says.
The study also found that reefs around rat-free islands were home to more herbivorous fish species. These fish help keep seaweed levels in check. This is good for corals, which often compete with seaweed for resources.
Scientists believe healthy coral ecosystems could help protect islands from erosion and sea-level rise, or at least slow their effects. Healthy reefs protect islands from surf and help soften the effects of storm surges, Hanson said.
Also, certain types of reef fish produce sand, which can wash up on islands and nourish sandy beaches. For example, parrotfish feed on algae and dead coral, digesting crunchy reef material and excreting it as sand.
Providing a healthy environment for this species of fish could help fortify islands from erosion and the effects of rising sea levels, Benquitt said.
“I don’t know if this is still happening,” she warned. “But that’s a reasonable hypothesis.”
None of these positive side effects can replace meaningful climate action, Benquitt added. As long as greenhouse gases in the atmosphere continue to increase, the effects of sea level rise, ocean heatwaves, ocean acidification, and climate change will all continue to get worse.
But these efforts will help buy the islands a little more time and give them a better chance in the meantime.
Island Conservation has set a goal of restoring 40 islands by 2030.
“Ocean health is a common issue,” says Hanson. “Biodiversity and extinction are common problems. Climate change, arguably what I am preaching to the choir here, is a great common problem. plug.”
The effort is “really bigger than any group or individual,” he added.
Reprinted from E&E News with permission of POLITICO, LLC. Copyright 2023. E&E News provides important news for energy and environmental professionals.
