The Latin America region is remarkably heterogeneous in terms of climate, ecosystems,
human population distribution, and cultural traditions. Land-use changes have
become a major force driving ecosystem changes. Complex climatic patterns, which
result in part from interactions of atmospheric flow with topography, intermingled
with land-use and land-cover change, make it difficult to identify common patterns
of vulnerability to climate change in the region. Water resources, ecosystems,
agriculture and plantation forestry, sea-level rise, and human health may be
considered the most important among the various sectors that may be impacted
by climate change.
Climate, Extreme Events, and Water Resources
In most of Latin America, there are no clear long-term tendencies in mean surface
temperature. Some changes in regional atmospheric circulation have been detected.
For instance, the south Atlantic anticyclone has intensified, and the subtropical
jet stream in South America has shifted south. These phenomena may be a sign
of changes associated with climate change as they already are impacted by the
El Niño-Southern Oscillation (ENSO) phenomena and extreme events.
The cryosphere in Latin America, which is composed of glaciers in the high
Andes and three major ice areas in southern South America, may be severely affected
by global warming. It has been well established that glaciers in Latin America,
particularly along the tropical Andes, have receded in recent decades. Glaciers
contribute to streamflow in rivers of semi-arid and arid areas of South America.
Streamflows in Andean riversfor example, in northwest Peruexhibit
tendencies that may be related to glacial extent changes before and after the
mid-1970s. However, there also is evidence that rainfall and river flows in
other regions of Latin America correspond only to interdecadal variability in
the hydrological cycle. For instance, rainfall and streamflow in Amazonia and
northeast Brazil exhibit interdecadal variability linked to Pacific and Atlantic
Ocean influences. Warming in high mountains also could affect mountain sports
and tourist activities, which represent an important source of income in the
economies of some countries in the region.
At a subregional level, precipitation trends in Latin America vary. Precipitation
trends depend on the location and the length of the time series under study.
For instance, negative trends in some parts of Central America (e.g., Nicaragua)
contrast with positive trends in northeastern Argentina, southern Brazil, and
northwestern Mexico. Other regions, such as central-western Argentina, do not
show well-defined trends. This suggests, for instance, an increase in precipitation
in some regions of the mid-latitude Americas.
The Amazon Riverby far the world's largest river in terms of streamflowplays
an important role in the water cycle and water balance of much of South America.
Several model studies and field experiments show that about 50% of the rainfall
in the region originates as water recycled in the forest. In the Amazon region,
even small changes in evapotranspiration affect water vapor fluxes. Therefore,
deforestation is likely to reduce precipitation because of a decrease in evapotranspiration,
leading to important runoff losses in areas within and beyond this basin. Any
reductions in rainfall would affect not only Amazonia but also Brazil's
central-south region, where most of the country's agriculture and silviculture
are located. However, with the current rate of deforestation of no more than
10% in Amazonia as a whole, discharge observations across the basin do not exhibit,
to date, any significant trends.
Although it is expected that tropical storms (e.g., tropical cyclones) will
increase their peak intensity under global warming (see Table
3-10), only some hints of such intensification in the tropical cyclones
affecting the Americas have been detected. Some studies based on model experiments
suggest that under climate change the hydrological cycle will be more intense,
with changes in the distribution of extreme heavy rainfall, wet spells, and
dry spells. Frequent severe droughts in Mexico during the past decade coincide
with some of these model findings. Even though it is uncertain how global warming
may affect the frequency and intensity of some extreme events, the infrequent
overlapping of hydrological and weather/climate events historically have given
rise to disasters, whose frequency may be enhanced by such warming.
It also has been suggested that under climate change, more El Niño-like
mean conditions will be experienced. El Niño differentially influences
precipitation and temperature in different parts of the region; for example,
it is related to dry conditions in northern northeast Brazil, northern Amazonia,
and the Peruvian-Bolivian Altiplano. Southern Brazil and northwest Peru exhibit
anomalously wet conditions during these periods. In Mexico and the Caribbean
coast of Central America, there is compelling evidence of more winter precipitation
and less summer precipitation during El Niño. Some of the most severe
droughts in Mexico in recent decades have occurred during El Niño years.
During the 1997-1998 El Niño event, droughts occurred in Amazonia,
Mexico, and Central America, favoring forest fires. Under climate change conditions,
the number of forest fires may increase.
Latin America contains a large percentage of the world's biodiversity,
and climate change could accelerate losses in biodiversity that already are
occurring. Some adverse impacts on species that can be related to regional changes
in climate have been observed. Studies show that climatic changes already are
affecting frogs and small mammals in Central America. The tropical forests play
an important role in the hydrological cycle of much of South America. Several
model studies and field experiments show that a large part of the rainfall in
the region originates as water recycled in the forest. Large-scale deforestation
is likely to result in increased surface temperatures, decreased evapotranspiration,
and reduced precipitation. Forest fragmentation and degradation has led to increased
vulnerability of forests to fire. Global warming and regional climate change
resulting from land-cover change may be acting synergistically to exacerbate
stress over the region's tropical ecosystems.
Mountain ranges and plateaus play an important role in determining not only
the Latin America climate and its hydrological cycle but also its large biodiversity.
Mountains constitute source regions of major rivers such as the Amazon, the
Parana, and the Orinoco. These river basins represent important habitats of
biological diversity and endemism and are highly vulnerable to extreme climate
On decadal to centennial time scales, changes in precipitation and runoff may
have significant impacts on mangrove forest communities. Sea-level rise would
eliminate mangrove habitat at an approximate rate of 1% yr-1. The rate is much
faster in the Caribbean mainland (approximately 1.7% yr-1). This problem is
causing a decline in some of the region's fisheries at a similar rate because
most commercial shellfish use mangroves as nurseries or refuges. Coastal inundation
stemming from sea-level rise or flatland flooding resulting from climate change
therefore may seriously affect mangrove ecology and associated human economy.
Agricultural lands (excluding pastures) represent approximately 19% of the
total area of Latin America. For the past 40 years, the contribution of agriculture
to the gross domestic product (GDP) of Latin American countries has been on
the order of 10%. Therefore, this economic sector remains a key element of the
regional economy. An important aspect of this sector is that a large percentage
(30-40%) of the economically active population works in this sector. Agriculture
also is an important element for the food security of the poorest sectors of
the population. Under climate change conditions, subsistence farming could be
severely threatened in some parts of Latin America, such as northeastern Brazil.
Studies in Argentina, Brazil, Chile, Mexico, and Uruguay based on general circulation
models (GCMs) and crop models project decreased yields in several crops (e.g.,
maize, wheat, barley, grapes), even when the direct effect of carbon dioxide
(CO2) fertilization and the implementation of moderate adaptation measures at
the farm level are considered. It is likely that increases in temperature will
reduce crop yields in the region by shortening the crop cycle. However, the
lack of consistency in the various GCM precipitation scenarios makes it difficult
to have a precise scenario for crop production under climate change, even when
the relationships between precipitation and crop yields are well known. Increased
temperature, ultraviolet radiation, sea-level rise, and changes in pest ecology
may threaten food production as well (e.g., in Argentina). Climate change may
reduce silvicultural yields as a result of changes in water availability during
the dry season.
The magnitude of the impacts of climate change on health in Latin America primarily
depends on the size, density, location, and wealth of the population. It has
been established that exposure to heat or cold waves has an influence on mortality
rates in risk groups in the region. The projected increase in temperature in
polluted cities, such as Mexico City or Santiago, may have an influence on human
health. There is evidence that the geographical distributions of vector-borne
diseases (e.g., malaria, dengue) in Brazil, Colombia, Argentina, and Honduras
and infectious diseases (e.g., cholera, meningitis) in Peru and Cuba change
when temperature and precipitation increase. The exact distribution of these
diseases, however, is not clear.
It is likely that extreme weather events will increase death and morbidity
rates (injuries, infectious diseases, social problems, and damage to sanitary
infrastructure), as during the heavy rains in Mexico in 1999 or in Venezuela
in 1999. On longer time scales, El Niño and La Niña cause changes
in disease vector populations and the incidence of water-borne diseases in Brazil,
Peru, Bolivia, Argentina, and Venezuela. Extreme climate events appear to affect
the incidence of allergies in Mexico. Some economic and health problems could
be exacerbated in critical areas, fostering migrations from rural and small
urban settlements into major cities and giving rise to additional stress at
the national level and, at times, adversely affecting international relations
between neighboring countries. Therefore, under climate change conditions the
risks for human health in Latin America may increase.
Adaptation Potential and Vulnerability
The economy of Latin American countries can be severely affected by extremes
of natural climate variability. There were more than 700 natural disasters in
the region between 1980 and 1998. For instance, Hurricane Mitch in 1998 resulted
in economic losses of approximately 40 and 70% of the gross national product
(GNP) in Nicaragua and Honduras, respectively. Poverty and unequal distribution
of wealth may increase as a result of the negative effects of climate change.
Trade agreements are becoming increasingly important for Latin American economies.
In principle, they have been designed mainly to speed up socioeconomic development.
However, various elements that relate to environmental issues gradually are
being introduced into these agreements, including provisions related to climate
change. Environmental issues are beginning to be reflected in the environmental
legislation in the region. For instance, environmental impact assessments are
now required in most project developments.
Although climate change may bring benefits for certain regions of Latin America,
increasing environmental deterioration, combined with changes in water availability
and agricultural lands, may reduce these benefits to a negligible level. The
adaptive capacity of socioeconomic systems in Latin America is very low, particularly
with respect to extreme climate events, and vulnerability is high.