South America: Climate Change Impacts

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South America: Climate Change Impacts

Introduction

South America is the fourth-largest continent, with a population of more than 370 million people. Its role in global climate revolves around the vast Amazon basin. As with other continents, South America is already experiencing some effects of climate change and is predicted to experience more.

As South America is overall an economically less developed area of the world, adaptation of human systems to climate change will be more difficult than in more developed areas such as North America, Europe, or Australia. Observed climate changes include shifts in precipitation and increased temperatures. Projected effects include more extreme weather events, species extinctions, water stress, decreased rice and soybean yields, and adverse impacts on coasts from rising sea levels.

Historical Background and Scientific Foundations

South America was first colonized by humans at least 12,000 years ago. Severe impacts on one of the world's most climatically important ecosystems, the Amazon river basin, began in the twentieth century and have

accelerated in recent decades. The huge Amazon basin, about three quarters of the size of the continental United States, contains about 20% of all plant and animal species in the world and is key to both local and global circulations of heat, moisture, and carbon.

The most important direct human impact on the Amazon is deforestation: about 7,700 square mi (20,000 square km) of forest, an area almost as large as the New Jersey in the United States, are now cut down each year for timber and to make way for highways, settlements, pasture for cattle, crops, and other purposes. Some 190,000 square mi (494,000 square km) of Amazon forest have been cut down since 1990.

Large changes in the Amazon will inevitably affect the climate of the region, the continent, and the entire world. Scientists have recently estimated that the Amazon basin forest is trapping about 100 million tons of carbon per year. (The carbon comes from carbon dioxide, which plants break up to obtain carbon for their tissues.) Due mostly to deforestation, carbon emissions from Brazil (whose share of the Amazon is more than half the size of the continental United States) rose by up to 50% from 1990 to 2003.

Further, global climate change will, in turn, affect the Amazon, a form of feedback that may accelerate climate change. For example, increasingly frequent El Niño events have already been documented. During these events, dry conditions prevail, reducing the forest's capacity to absorb carbon. Replacing forest with open space strengthens this feedback, as pasture land releases less moisture to contribute to rains.

According to Dan Nepstad, an American scientist working with the Amazon Institute for Environmental Research: “Even with current rainfall systems, many forests ‘in the Amazon’ are coming close to the limit where they shed their protective layer and become vulnerable to burning or slowed-down growth and die.”

The United Nations Intergovernmental Panel on Climate Change (IPCC) stated in 2007 that there was still only inconclusive observational evidence of changes in water cycles in the region due to deforestation, but agreed that deforestation may in the future cause regional climate changes that could lead to the transformation of much of Amazonia to savanna. Savanna is a type of dry woodland with widely spaced trees—profoundly different from the existing rainforest and much less effective at sopping up carbon.

According to the IPCC's report Climate Change 2007: Impacts, Adaptation and Vulnerability, signs of climate change already being observed in South America include the following:

In recent years, all of Latin America has been severely affected by climatic variability and extreme weather events. These effects include intense rainfall, flooding, drought in the Amazon, and Hurricane Catarina in 2004 (not to be confused with Hurricane Katrina of 2005), the first known hurricane-sized tropical cyclone to occur in the South Atlantic.
During the last few decades, shifts in temperature and precipitation have occurred. Rainfall has increased in southeast Brazil, Paraguay, Uruguay, and parts of Argentina. Rain has declined in southern Chile, southwest Argentina, and southern Peru.
Land-use changes (including deforestation) have degraded land and may have changed the weather. There is evidence that smoke from burning forests has changed regional temperatures and rainfall in southern Amazonia, as well as injuring human health by polluting the air.

WORDS TO KNOW

DEFORESTATION: Those practices or processes that result in the change of forested lands to non-forest uses. This is often cited as one of the major causes of the enhanced greenhouse effect for two reasons: 1) the burning or decomposition of the wood releases carbon dioxide; and 2) trees that once removed carbon dioxide from the atmosphere in the process of photosynthesis are no longer present and contributing to carbon storage.

EL NIÑO: Regularly recurring warming of the surface waters of the eastern Pacific that has affects on global climate; part of the El Ninño/Southern Oscillation Cycle (ENSO). In some contexts, “El Ninño” refers to the entire ENSO cycle.

GLACIAL RETREAT: Melting and shrinkage of glaciers at the end of a glacial cycle.

GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change.

HYDROPOWER: Electricity generated by causing water to flow downhill through turbines, fan-like devices that turn when fluid flows through them. The rotary mechanical motion of each turbine is used to turn an electrical generator.

Impacts and Issues

Likely impacts of future climate change on South America, according to the IPCC, include accelerated glacial retreat in the Southern Andes mountains, reducing availability of water for hydropower and other uses. Deforestation will interact with climate change to produce greater fire risk, already a problem in the region. Projected average warming for Latin America to 2100, depending on what assumptions are made about ongoing greenhouse-gas emissions, range from 1.8 to 10.8°F(1to6°C). The frequency of weather and climate extremes will likely increase, including frequency and intensity of hurricanes in the Caribbean. The number of people experiencing water shortages due to climate change will probably be between 7 and 77 million.

Scientists remain uncertain about exactly what the role of the large, complex Amazon area is on global climate. For example, the amount of carbon dioxide actually absorbed by a typical acre of Amazon rainforest is still not known. As with other regions, all predictions about the future effects of climate change on South America include ranges of uncertainty: effects may be larger or smaller than predicted. Historically, scientific predictions have tended to underestimate, not overestimate, global warming and sea-level rise.

BIBLIOGRAPHY

Books

Parry, M. L., et al, eds. Climate Change 2007: Impacts, Adaptation and Vulnerability: Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press, 2007.