Unexpected Victims of Climate Change

Polar bears serve as the poster children for climate change. But global warming also threatens many other species that don't get as much news coverage.

Moose in the Rocky Mountains become the latest climate change catastrophe icon recently, as their populations have plummeted with warming temperatures. But it's not just heat stress that is killing them off. Biologists are finding brain worms, liver flukes and ticks, as many as 150,000 on a single moose, are infecting the population to death.

Increased temperatures are allowing northern forest ticks to survive over the winter, when the blood-suckers and their eggs would normally die. This leaves an infected moose with no respite as the ticks breed again in the spring. The moose will continue to scratch and rub off its fur, develop anemia, and eventually die of emaciation.

Orangutans' populations on Borneo and Sumatra have declined by more than 80 percent during the last 75 years, according to the International Union for the Conservation of Nature (IUCN). Most of that decline resulted from hunting and habitat loss as the forests were logged for timber and to make room for oil palm plantations.

Climate change may further reduce the animals' homeland, according to a study in PLOS ONE. The orangutan lives most of its life swinging in the trees and the animals' forest home faces threats of drought and fire as climate change alters weather patterns.

The koala's picky eating habits may doom it as the planet's atmosphere changes. Koalas dine solely on the leaves of eucalyptus trees. Increasing levels of carbon dioxide in the air do speed up eucalyptus growth, but the leaves have lower nutritional value. Koalas need to eat more leaves to get the same amount of nutrition, according to the IUCN.

As it warms up Down Under, more forest fires and droughts threaten koalas' arboreal abodes. The IUCN named the koala as one of 10 flagship species, besides polar bears, that exemplify the effects of climate change.

Like orangutans and koalas, the Haleakalā silversword (Argyroxiphium sandwicense macrocephalum) lives in a fragile habitat and would be in danger of disappearing even if the planet weren't changing. Livestock and flower-collectors nearly wiped out the plant early in the last century. Conservation programs helped the plant bounce back, but climate change has erased much of that progress, according to research in Global Change Biology. The population of the plant dropped from 65,000 in 1991 to 28,492 in 2010 as its highland habitat became warmer and dryer.

The silversword grows only on the volcanic slopes of Mount Haleakalā on the island of Maui. The plants can grow for nearly a century until it finally produces hundreds of vibrant reddish blossoms on a six-foot spike at the end of its life cycle. One to two million tourists hike to see the plants each year as they stand out against their bleak, lava-scourged surroundings.

The Grinch has nothing on global warming. Higher temperatures in the southern United States endanger Christmas tree plantations. During the 2011-12 season, heat and drought killed 80 percent of seedlings and 10 to 20 percent of mature trees on some Tennessee tree farms, according to the Tennessee Department of Agriculture.

Christmas trees do their part to fight climate change and help animals. The trees suck carbon dioxide from the air and store it in their tissues. After harvest, some of that carbon remains trapped underground in the roots. Real trees also provide habitat for wildlife.

Like the silversword, the right whale just can't catch a break. After being nearly wiped out by whalers, the North Atlantic species of right whale now suffers as climate change influences fluctuations in the whale's main food source, the tiny plankton Calanus finmarchicus. Climate change affects their populations by altering seawater temperatures, along with wind and water currents.

Between 1997 and 1999, plankton plummeted in the North Atlantic. In 1999, only one right whale was born, the lowest on record, according to the New England Aquarium. Several years passed before right whale births returned to normal. Less than 500 North Atlantic right whales survive.

The U.S. Endangered Species list already holds six sea turtle species: green turtles, hawksbills, loggerheads, Kemp's ridleys, Olive ridleys and leatherbacks. To add to the turtles' troubles, climate change poses another attack. First, rising sea levels wash away prime nesting grounds on tropical beaches, especially in places like the Maldive Islands that were never far above the sea to begin with.

Second, as the temperature of the sand on those disappearing beaches increases, it's almost too hot for turtle eggs to incubate safely. Once the sand reaches 34 degrees Celsius (93 degrees Fahrenheit), the turtle eggs get cooked. Even before the sand reaches a deadly temperature, it influences the sex ratio of the offspring. At warmer temperatures, more females develop than males.

However, a study in Conservation Biology found that the males that are born work extra hard to fulfill their paternal duties and visit breeding grounds twice as often as females, which could reduce the effects of the female domination of the turtle dating pool.

A short-eared relative of rabbits, the American pika may be adorable, but a pretty face won't save it from losing its home to hot weather.

The pika lives in the mountains of the western U.S. During the past decade, local extinction rates have increased five-fold, according to research in Global Change Biology. Warmer temperatures forced the pika to shift its homeland further up mountainsides at a rate of 145 meters (475 feet) per decade since 1999. Mountains don't continue skyward forever, so eventually the pika will run out of suitable habitat.

On the other end of the food chain from pikas, even the mighty Bengal tiger may succumb to climate change pressure. Rising sea levels could drown the habitat of Bengal tigers on the coast of Bangladesh and India. A study in Climatic Change estimated that a 28-centimeter (11-inch) rise in sea level would submerge 96 percent of the tigers' remaining habitat in the Sundarbans, the world's largest block of mangrove forest, located along the coast of Bangladesh and India.

Human pressures on tigers, mainly hunting and deforestation, have already driven some species, such as the Bali and Javan tigers, into extinction.

Along with koalas, the IUCN designated corals in the Acropora genus -- such as finger, staghorn and elkhorn corals -- as species that presage climate change. Approximately 160 species of these corals comprise one-fifth of planet's reef corals. Rising sea temperatures harm coral polyps, the tiny creatures that form the living, growing outer layer of coral. When too many of these creatures die, it causes coral bleaching. The dead reef skeleton turns white because the colored algae that lived with the polyps disappeared.

In addition to the loss of coral polyps, increased carbon dioxide in the atmosphere also raises the levels of carbonic acid in the ocean. The carbon dioxide dissolves into the water. The resulting rise in acidity dissolves the calcium carbonate building blocks of the reef's skeleton and makes it more difficult for coral polyps to add new calcium layers to the reef.

Despite Rachael Carson's warning, spring may indeed become silent as migratory songbirds die off. The egg-weakening pesticides that Carson wrote about may be outdone by climate change. Many songbirds depend on timing their migrations from the South with the arrival of spring in the North. However, signs of spring arrived an average of one to 1.5 days earlier each decade since the 1950s in the Northern Hemisphere, according to research in Global Change Biology.

Migratory birds can have a hard time adapting. For example, one study in Nature documented that pied flycatchers (Ficedula hypoleuca) populations had declined by 90 percent in some regions. The bird's populations dropped most sharply in regions where the earlier onset of Spring caused food availability to peak before the bird's breeding season. Hungry chicks starved because they hatched too late for the spring smorgasbord.