Supplemental Material
Imagine a planet where jellyfishrule the seas, giant rodents roam the mountains and swarms of insects blur everything in sight. It may sound far-fetched, but enough global warming is likely to change the distribution of wildlife on Earth. While species that are under threat, such as the polar bear, seem to get all the attention, others are beginning to thrive like never before.
In the past three months, new studies have been published about killer whales, wandering albatross and trumpeter swans—all of which appear to be benefiting from climate change.
Melting ice is turning the Arctic Sea into a giant buffet for killer whales. They have been arriving in growing numbers to feed on belugas, seals and narwhals, according to a recent study by scientists from the University of Manitoba. Warmer temperatures make it easier for the whales to hunt because their prey is less likely to climb onto sea ice or hide below it to escape.
At the opposite end of the world, in Antarctica's Southern Ocean, changing winds have been helping the wandering albatross find food faster. Researchers say global warming has produced stronger air currents that allow the birds to spend less time away from their nests, increasing the odds that their chicks will survive.
"The duration of foraging trips has decreased, breeding success has improved and birds have increased in mass by more than 1 kilogram," wrote the study's authors, who called their findings "positive consequences of climate change."
In Arctic areas, global warming is happening at roughly twice the average speed, which has allowed Alaska's trumpeter swans to expand their breeding grounds northward into regions that were previously too cold, according to a study published in Wildlife Biology in December.
"We knew that the population was expanding, both in numbers and spatially on the landscape," said Joshua Schmidt, a biometrician for the National Park Service Inventory and Monitoring Program and a co-author of the study.
Ice age veterans swan around
After analyzing more than 40 years of data, researchers discovered the swans were benefiting in two ways from global warming: They had expanded their territory northward, and they were seeing about three more snow-free days than before 1940. These shorter winters mean the swans—which were hunted to the brink of extinction in the 1800s—now have more time to eat and grow strong before embarking on a long migration to the Pacific Northwest each fall, improving their chances for survival.
"Swans have been through an ice age or two, so climate change isn't something they haven't seen before," said James King, a biologist who used to work for the U.S. Fish and Wildlife Service in Alaska. After studying swans for about 50 years, King believes the birds "know how to deal with climate change." Historically, they have found ways to outsmart the cold by nesting near hot springs, which prolongs their breeding season, he said.
"There will definitely be some animals that will do better with longer summer and milder winter," said Paul Curtis, an extension wildlife specialist at Cornell University. "Fifty years from now, central New York may be as warm as North or South Carolina. It's a much faster change than we've seen any time historically, and it's just a question of how some of these species will respond."
White-tailed deer in the northern United States are already showing a population boom thanks to this year's lack of snowfall, which has made it easier for the animals to find food, said Curtis. He also believes a warmer spring could benefit snakes and salamanders, giving them more time to grow and add to their fat reserves.
A 2010 study in the journal Nature reported that yellow-bellied marmots in Colorado's Rocky Mountains are also flourishing thanks to climate change. The squirrel-like mammals can lose up to 40 percent of their body mass during hibernation, and longer summers are giving them more time to eat and store fat, helping them live through the winter and reproduce the following year. The adult marmots have gained half a pound on average and their numbers have more than doubled from 2000 to 2010, said researchers.
Acid-loving jellyfish?
Jellyfish populations are also suspected to be swelling because of climate change. In recent years, the creatures have been clogging the nets of fishermen, stinging record numbers of beachgoers and blocking the water intake lines of power plants in at least three countries. Some scientists are linking the phenomenon to warmer waters and ocean acidification caused by high levels of carbon dioxide in the atmosphere. Studies have found that today's oceans are 30 percent more acidic than in the 18th century, when the Industrial Revolution began.
However, a lack of historical data on jellyfish populations has caused some scientists to question whether the apparent boom is actually connected toglobal warming. A project called the Jellyfish Database Initiative was recently launched to determine whether the increases are happening on a global scale and if they could be part of a natural cycle.
Another creature that is likely to flourish in warmer waters is theSchistocephalus solidus tapeworm. The parasite spends most of its life growing inside the three-spined stickleback fish, which is about the size of a small sardine and lives in oceans and lakes throughout the Northern Hemisphere.
Scientists at the University of Leicester placed infected sticklebacks into a tank of water at 68 degrees Fahrenheit—about 9 degrees warmer than a typical summer's day in Britain—and found the tapeworms to grow four times faster than normal. The ordinary worms were able to produce about 12,000 eggs, while the larger worms laid almost 200,000, according to data published in the journal Global Change Biology in November.
Certain species of insects, like mosquitoes, ticks and invasive beetles, are also expected to benefit from warmer temperatures. In fact, a 2003 study published by the Ecological Society of America concluded that "all aspects of insect outbreak behavior will intensify as the climate warms."
Fewer ticks, fleas and beetles freeze
Extreme cold spells can kill a percentage of hibernating insects each winter, says Jody Gangloff-Kaufmann, a professor of entomology at Cornell University. Without these cold spells, more insects are likely to emerge in the spring.
"I anticipate the mosquito problems we normally see to be much more intense and begin earlier than usual if the weather continues to be mild," said Kaufmann, who believes ticks and fleas will also be able to feed more frequently thanks to warmer winter days.
Future levels of carbon dioxide may help beetles, as well, according to researchers from the University of Illinois, Urbana-Champaign, who found that Japanese beetles lived longer and laid more eggs after eating leaves that were grown in an environment with additional carbon dioxide.
"What we really don't know is what the long-term consequences of climate change are," explained Curtis. "There will definitely be winners and losers, and it's hard to predict what some of those will be." He said animals that can migrate—like whales and birds—are more likely to adapt, while species bound to a particular environment, or food source, will face greater challenges.
Even creatures that appear to be benefiting today may not be so lucky in the future.
Scientists predict the winds that are helping the wandering albatross will become increasingly violent by the end of the century, threatening the birds' survival. And Colorado's marmots don't easily adapt to heat, so rising temperatures may soon put them—and the plants they eat—at risk.
"It's hard to say if swans will even benefit long-term," said Schmidt, who explained that the ponds they live in may already be drying up. "If those sorts of things are occurring, it might be a zero-sum game. Or it might be negative."
No comments:
Post a Comment