Tuesday, February 05, 2013

Palmyra Cleared of Rats, Now to Clear Plastic

Fairy tern, credit: Erik Oberg
The remote central Pacific atoll of Palmyra has one less species living in paradise. Black rats were an invader responsible for damaging native species until man took action to remove them from the shreds of palm covered land floating in a vast blue ocean. Twenty-five islets only cover 580 acres, but the seas surrounding contain thousands of acres of healthy coral reefs. In 2009 Palmyra was included in the Pacific Remote Islands Marine National Monument. Rats could probably not have reached Palmyra without man's intervention so removing them artificially was an ecologically appropriate action. Around 30,000 rats were exterminated to protect ten seabird species which use the US administered atoll for nesting. The agency used a rodenticide with a proven track record in similar island clearances. The rare flowering tree Pisonia grandis is also expected to benefit from the extermination. Rats eat eggs and chicks of ground nesting birds as well as land crabs, seeds, and tree seedlings. Black rats made there way to Palmyra during WWII, most likely aboard US Navy and merchant marine ships. The clearing of rats is the first step in a ecological project intended to restore the atoll's natural balance. Last summer conservationists associated with University of California Santa Cruz found a 367% increase in arthropods, a 130% increase in native tree seedlings including the first recorded seedlings of Pisonia, and no change in the number of bristled thigh curlews, a threatened bird species for which special care was taken to prevent harm from the rat removal.

Wisdom feeds her latest chick
Now that Palmyra is being restored, perhaps our attention should turn to cleaning up another man-made killer of Pacific wildlife, plastic. Some species are heavily impacted by visible plastic debris that are washed up and accumulated on islands in the central Pacific gyre. An example is the Laysan Albatross (Phoebastria immmutabilis) nesting on Midway Atoll. {"Midway Island"} Chicks pecking for food ingest plastic junk to such as extent that reduced their food intake which leads to dehydration and death. Parent birds unknowing feed as much as 5 tons of plastic debris to their chicks. Lead poisoning from paint chipping off abandoned buildings is also a source of toxicity. Despite the man-made hazards these impressive flyers cling tenaciously to life. Recently the oldest recorded albatross of 62 years, appropriately named "Wisdom" hatched a healthy chick for the sixth consecutive year. The bird has probably raised 30 to 35 chicks in her life, but the figure may be more since experienced birds make better parents. Wisdom has worn out five bands over the last six decades, making her the oldest known bird in the world. The albatross is a source of inspiration to staff and volunteers tasked with monitoring the health of seabirds that arrive in the hundreds of thousands to nest in the Midway Refuge. The survey is one of the oldest of tropical seabirds in the world.

credit: Emma Teuten
Visible plastic debris such as those despoiling Midway and other Pacific islands are not the only ocean pollution problem. Plastic trash has bee around long enough that it has degraded in seawater. Microplastics or particles of plastic the size of plankton or smaller enter the food chain of marine organisms. [photo] Bivalves--clams, mollusks and oysters--which filter the water for food are especially affected. Clams can be turned into hermaphrodites by ingesting microplastics because they mimic hormones like estrogen. They also act as sponges soaking up toxins such as tributyltin used in marine paint. Of 504 fish taken from the English Channel and examined, more than a third was found to contain microplastics in their guts. The contamination could pose serious physical consequences for fish, creating digestive blockages or causing a false sense of satiation. The study was published in Marine Pollution Bulletin. Plastic pollution can be relatively easy to correct by conscienciouly recycling plastic products and eliminating products that are potentially hazardous if disposed of improperly. But man must also clean up the mess he has made with more than a half century of using and dumping plastic.