(33) Climate Science

 Species Extinction


Species Extinctions

Throughout Earth history, species of plants and animals have gone extinct. This happens more often when conditions are difficult, such as they are after an asteroid impact or during a massive flood basalt eruption. Extinction rates are lower when conditions are more stable. In recent decades, species extinctions have risen to about 1,000 times the normal background rate. These extinctions are due mainly to human activities, primarily changes in land use. The conversion of tropical rain forests to ranchland, for example, results in a tremendous loss of species. In the future, warmer temperatures will destroy the delicate balance many species have with their environment, which will trigger their extinction. The loss of important species could cause entire ecosystems to collapse.

So far, the extinction of only one species has been directly attributed to global warming, and even then not all scientists agree that warming is entirely to blame. That species was the Monteverde Golden Toad (Bufo periglenes), formerly found in a Costa Rican nature preserve called the Monteverde Cloud Forest. The extinction came suddenly, between 1987, when an American ecologist, Martha Crump, counted about 1,500 Golden Toads during mating season, and 1988, when she returned to find no breeding toads-and none have been found since.

Scientists blame the extinction on the chytrid fungus (Batrachochytrium dendrobatidis), which destroys the frogs’ skin, ultimately killing them. Although the Monteverde and other Central American cloud forests are usually covered in mist, on sunny days the toads rid themselves of the fungus by basking in the sun and raising their temperatures above 86°F (30°C). However, warmer air temperatures increased the amount of cloud cover over the mountain. This reduced the amount of sunlight, so the toads could not raise their body temperatures high enough to kill off the fungus.

The chytrid fungus is responsible for population declines or extinctions in at least 100 species of amphibians in the United States, Central and South America, Europe, New Zealand, and Australia. Amphibian populations are plummeting globally; nearly one-third (1,856) of the 5,743 known amphibian species are threatened, and more than 100 have likely gone extinct since 1980, according to the Global Amphibian Assessment. Habitat destruction, pollution, and disease are taking an enormous toll, but global warming is a factor in many of these extinctions. As evidence, 78% to 83% of the known extinctions occurred in years that were unusually warm across the tropics. Like the Monteverde Golden Toad, several amphibian species were last seen in 1988, following a very hot 1987.

In the oceans, the extinction of phytoplankton due to acidification and rising temperatures could initiate a collapse of ocean ecosystems. This acidification will also harm larger organisms. A model published in Nature by James C. Orr and other scientists in September 2005 projected that organisms such as coral, shellfish, and sea stars could have trouble forming their shells in Southern Ocean surface waters as soon as 2050 and in a larger area by 2100. Warmer seawater temperatures would lower the amount of oxygen, which would also be detrimental to ocean life. Warmer temperatures are already causing some species to move to new locations. Studies show that land plants and animals will need to move pole ward 60 to 90 miles (100 to 150 km) or upward 500 feet (150 m) for each 1.8°F (1°C) rise in global temperature. Native species may be driven out of the area by more heat-tolerant nonnative species. If a species cannot move or overcome competition from nonnative species, it will become locally extinct.

If the species has a small distribution, or if it experiences problems throughout its range, it will go extinct. As a result, biodiversity-the number of species in a given habitat-will decline.

Some species have so far been successful at moving to more favorable climate conditions, as the Parmesan and Yohe study showed. However, in a 2006 article in the New York Review of Books, NASA’s James Hansen said that during the time the scientists chronicled range changes in these species, average temperatures moved pole ward at more than eight times that pace (35 miles, or 56 km, per decade). Species are not keeping up, and this could cause future population declines. Also, if projected temperature increases follow the business as usual model, temperatures will move toward the poles at double the current rate, at least 70 miles (113 km) per decade. Most species will not be able to migrate this fast, which will likely result in many extinctions. The species that are most at risk are those species that live in the Polar Regions and on mountaintops: They would have nowhere to move.

During Earth history, many organisms seemed to be able to adapt to times of rapid climate change and did not go extinct. But higher temperatures are not the only stress humans are placing on the other inhabitants of Earth. Organisms cannot move in response to changing climate if they run into farms, urban sprawl, or pollution. In his book The Weather Makers, Tim Flannery calculates that in a business-as-usual scenario, and taking into account the other stresses human are causing, about 60% of Earth’s species could go extinct. Using the alternative scenario, in which people significantly reduce greenhouse gas emissions, the number is 20%. Of course, these numbers cannot be established with any certainty. Says NASA’s Hansen, “Life will survive, but it will do so on a transformed planet. For all foreseeable human generations, it will be a far more desolate world than the one in which civilization developed and flourished during the past several thousand years.”

Even scientists making the direst predictions of species extinction take a longer term view. A mass extinction caused by climate change will wipe out many of the species currently on the planet, but ultimately the Earth will stabilize, and new species will evolve that are adapted to the new conditions. Although some ecosystems and organisms will suffer greatly, humans are as dependent on the status quo as any species, so they will likely suffer as much as any organism.

 Climate Refugees

Refugees are people who have nowhere to go. Traditionally, refugees have been displaced due to war or political persecution. Now a new type of refugee is being proposed: Environmental refugees, those who are displaced from their homes by environmental changes. Although no organization yet recognizes them, they may already number 25 million. A large subcategory of environmental refugees is climate refugees-people who are displaced by increases in extreme weather events, sea level rise, or any other effect of climate change. Climate refugees are beginning to leave the small, inhabited islands of the southwestern Pacific Ocean. Many of these islands are low-lying coral atolls that may rise only a few feet above sea level.

Rising seas and storm surges damage homes and reduce the atoll residents’ ability to support themselves. According to the Red Cross in 2005, the number of people in the southwestern Pacific that have been affected by weather-related disasters has increased 65 times in the past 30 years. Many of these people have already become, or soon will become, climate refugees. Residents of the Carteret Islands are the first refugees being driven from their homes by rising seas. These six tiny horseshoe-shaped coral atolls are part of Papua New Guinea. The nearly 1,000 inhabitants have been trying to save their home for 20 years by planting mangroves and building seawalls. Despite their efforts, high tides and storm surges wash over the island, destroying homes and coconut palms and contaminating crops and freshwater supplies. Waves have broken off small pieces of the coral atolls. Scientists predict that the islands will be totally submerged by 2015. In 2005, the Papua New Guinea government decided to move 10 families at a time to a new, larger island home on Bougainville, a four-hour boat trip away.

The Carteret Islanders are a small group. Other locations, with bigger populations, could create many more climate refugees, which makes for additional problems. Densely populated Indonesia could lose about 2,000 islands by 2030. Extremely remote Tuvalu, the world’s second smallest nation (after Vatican City), with only 11,600 residents, is already losing people. Many of the residents of Tuvalu’s nine islands have already left their homes for New Zealand, where they try to maintain their unique culture while working and living among the New Zealanders. Although for many years Tuvaluans have left their islands because of overcrowding or in search of better jobs, island flooding due to climate change is increasingly cited as a motivation for evacuation. Some Tuvaluans are fighting to protect their island homes. The islanders have even sent an ambassador to the United Nations to tell the world of their plight. Tuvaluan ambassador Enele Sopoaga told writer Alexandra Berzon, for a 2006 article, “Tuvalu is Drowning,” in the online magazine Salon, “Tuvaluans want to live in their own islands forever. To relocate is a shortsighted solution, an irresponsible solution. We’re not dealing here with Tuvalu only. All of the low-lying island coastal areas are going to be affected.”

Island nation residents are not the only ones who have to worry about becoming climate refugees. Enormous numbers of climate refugees will come from developing nations, too. Climate change could create 250 million refugees in China, 150 million in India, and 120 million in Bangladesh, for example. As climate refugees are displaced in ever-increasing numbers, the question of what to do with them will be more crucial. New Zealand has agreed to take 75 Tuvaluans per year on a special permit, and others have gone to Australia or other island nations. But what happens when the numbers of climate refugees seeking asylum rises into the millions? Indeed, the third Inter-governmental Panel on Climate Change (IPCC) report in 2001 states there may be 150 million environmental refugees by 2050. Some people say that the nations most responsible for climate change should take most of the refugees, and suggest that the obligations should be proportional to the nation’s impact. In other words, the United States, which produced around 30% of the CO2 emissions during the twentieth century, would take about 30% of climate refugees, which would be as many as 250,000 to 750,000 people a year. Andrew Simms, head of the climate change program at the New Economics Foundation, wrote in the Guardian in 2003 that the advantage to this strategy would be that “Creating new legal obligations to accept environmental refugees would help ensure that industrialized countries accept the consequences of their choices.”

But the United States will not just need to take on foreign refugees-it will already have many of its own. Sea level rise will eventually make much of the Gulf of Mexico and South Florida coasts, as well as many coastal cities, uninhabitable. Eventually, as many as 50 million people could be flooded out. The New Orleans residents displaced by Hurricane Katrina could be considered to be climate refugees, although they are not the nation’s first: the Dust Bowl of the mid-to late-930s, which created over 500,000 refugees, was partly caused by a massive drought.


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