Miguel Cifuentes Jara
Tropical Agriculture Research and higher Education Center (CATIE) Climate Change Program Turrialba, Costa Rica, 2010 The Tropical Agricultural Research and Higher Education Center (CATIE) is a regional center dedicated to research and graduate education in agriculture and the management, conservation and sustainable use of natural resources. Its members include the Inter-American Institute for Cooperation on Agriculture (IICA), Belize, Bolivia, Colombia, Costa Rica, the Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Paraguay, Venezuela and Spain.
© Tropical Agriculture Research and higher Education Center, CATIE, 2010
Technical editors Editor Enric Aguilar, Ph.D. Elizabeth Mora Climate Change Research Group Geography Department Copy editors University Rovira i Virgili de Tarragona Joselyne Hoffmann Av. Catalunya, 35 Cynthia Mora 43002, Tarragona Spain Designer Rocío Jiménez Salas Víctor Orlando Magaña Rueda, Ph.D. Center for Atmospheric Sciences Translator Universidad Nacional Autónoma de México Christina Feeny Ciudad Universitaria Mexico City 04510 Mexico Contents
Introduction ...... 5 Key concepts of global climate change ...... 7 Climate and the greenhouse effect ...... 7 Climate change ...... 8 Natural climate variability ...... 9 Planetary movements ...... 9 Solar radiation ...... 10. Volcanic eruptions ...... 11 Human influence on climate ...... 11 Greenhouse gases (GHG) ...... 11 Aerosols ...... 13. The unequivocal human action ...... 14. Evidence of climate change ...... 16. Temperature ...... 16. Precipitation ...... 17. Changes in the oceans ...... 18. Ice and snow cover ...... 19. Extreme events ...... 19. Climate scenarios ...... 21. IPCC carbon emissions scenarios ...... 22. The importance of considering several scenarios ...... 24. Projections of future climate change ...... 24. Areas of uncertainty in the predictions ...... 26.
Climate in Mesoamerica ...... 29. Historical climate patterns ...... 29. Precipitation ...... 29.
3 ABC of Climate Change in Mesoamerica
Temperature ...... 31. Changes observed in climate variables ...... 31. Climate scenarios for Mesoamerica ...... 35. Expected changes in temperature and precipitation ...... 36.
Effects of climate change on Mesoamerica ...... 41. Water resources ...... 44. Biodiversity ...... 45. Climate change severity index ...... 48. Terrestrial ecosystems ...... 49. Aquatic ecosystems ...... 52. Freshwater systems ...... 52. Mangrove forests and coral reefs ...... 53. Coastal zones ...... 54. Fisheries ...... 55. Agriculture and cattle ranching ...... 56. Generalities of the sector ...... 56. Changes in production ...... 57. Human health ...... 59. Disasters ...... 60. Other sectors ...... 62.
Bibliography ...... 63. Annex 1 ...... 73. Annex 2 ...... 80.
Human activities have brought about changes in the natural func- tioning of the Earth’s climate system. Potential effects are varied and affect all areas of human endeavor. The scale of the changes and a limited capacity for response make Mesoamerica the region most vulnerable to climate change in the entire tropical region. In the face of this threat, it is essential to have access to high quality informa- tion to better understand the scope of the potential effects of climate change and design strategies to address them.
The purpose of this document is to provide up-to-date scientific information to support the formulation of the Regional Strategy on Climate Change for Central America and the Dominican Republic. The strategy aims to guide the actions of different sectors, institutions and organizations (governmental, private and civil society) to respond more effectively to the impacts and challenges of climate change. It will also help the countries of the region to position themselves in the global process of discussion and negotiation on climate change.
This document consists of three main parts. The first contains a detailed description of the processes that generate climate on Earth, the role played by human activities in influencing climate, the scientific evi- dence related to climate change and an analysis of climate scenarios. The second part of the document contains a summary of historical cli- mate patterns in the region, the changes observed in recent decades and the predictions for future climate. The third section offers a synthe- sis of the potential impacts of climate change on those sectors of society which, according to the Intergovernmental Panel on Climate Change (IPCC), would be most affected by climate change.
Key concepts of global climate change
1 Key concepts of global climate change
Climate and the greenhouse effect
Climate is defined as the set of states and changes in atmospheric conditions observed in a given area over a period of at least 30 years. Average conditions, together with their variability, and extreme events of precipitation, temperature, wind, atmospheric pressure, etc. are all expressions of a region’s climate. The climate of an area is a dynamic phenomenon subject to variability and change.
Solar radiation is the main source of energy for the planet’s climate system. More specifically, the balance (known as “radiative balance”) between the energy received by our planet from the sun, and energy that it re-emits, is the main mechanism that determines the Earth’s climate. To balance the amount of incoming energy absorbed, the Earth must radiate approximately the same amount of energy back to space. This occurs in the form of long wave energy, also known as thermal radiation. Approximately 30% of the solar energy reaching our planet is reflected directly back into space by the highest layers of the atmosphere and by surfaces with a high albedo1, such as those covered with ice and snow. The remaining two-thirds of the incident energy are absorbed by Earth’s surface and by the atmosphere.
Some trace gases in the atmosphere (carbon dioxide, methane, among others) absorb a large amount of thermal radiation emitted by the surface of the planet and radiate it back to Earth again. This natural
1 Albedo is a fraction of solar radiation reflected by a surface or an object, often expressed as a percentage.
7 ABC of Climate Change in Mesoamerica
phenomenon is known as the “greenhouse effect” and results in the warming of the planet’s surface (Figure 1). If the natural greenhouse effect were not in place, the temperature of Earth’s surface would be -18 ºC and would fluctuate widely between day and night. Therefore, the natural greenhouse effect makes life as we know it possible on Earth.
Atmospheric trace gases that directly contribute to the greenhouse effect are commonly known as “greenhouse gases” or “GHG”. The main greenhouses gases that contribute to global warming are water vapor and carbon dioxide (CO2). Other important GHG are methane
(CH4), nitrous oxide (N2O), ozone (O3), among others. Human activi- ties have increased the concentrations of carbon dioxide, methane, chlorofluorocarbons, etc. in the atmosphere, further intensifying the greenhouse effect and thereby increasing Earth’s surface temperature.
The climate system changes over time under the influence of its own internal mechanisms (such as El Niño/Southern Oscillation) and also because of external factors known as natural drivers or “forcings”. Some of the most important external natural forcings affecting cli- mate are variations in solar activity, planetary movements, volcanic eruptions and changes in the composition of the atmosphere.
Recently, scientists have determined that human activities—more specifically, increases in concentrations of greenhouse gases in the atmosphere—have become a dominant external forcing on the cli- mate, being responsible for most of the warming observed in the last 50 years. This phenomenon, is popularly known as “global warming”, or more broadly as “climate change” when other effects are considered.
The IPCC definition of “climate change” does not distinguish between natural and anthropogenic causes of climate change, whereas the
8 Key concepts of global climate change
Figure 1. Idealized model of the greenhouse effect. From Solomon et al. (2007). definition of the United Nations Framework Convention on Climate Change (1992) describes this process as “a change of climate which is attributed directly or indirectly to human activity that alters the com- position of the global atmosphere and which is in addition to natural climate variability over comparable time periods.”
Natural climate variability Planetary movements Long before human presence on Earth, the planet’s energy balance, and therefore its climate, was affected by various natural causes. For example, there is strong evidence showing that ice ages occur peri- odically and that these are linked to variations in Earth’s orbit. These changes are known as “Milankovitch cycles” (Figure 2), which are regular variations (in the order of hundreds of thousands of years) in the eccentricity of Earth’s orbit around the Sun, and changes in
9 ABC of Climate Change in Mesoamerica
Earth’s obliquity2 and precession3. Such variations in the planet’s movements alter the amount of incoming solar radiation received by the planet at different latitudes, producing drastic changes in the global climate.
Solar radiation Another likely cause of climate change is the variation in the amount of energy produced by the Sun. For example, sunspot observations as well as data from isotopes generated by cosmic radiation, show that solar radiation varies (by nearly 0.1%) in short 11-year cycles and also over much longer periods.
Figure 2. Diagram of Earth’s orbital changes (Milankovitch cycles) that drive ice age cycles. T denotes changes in the tilt (or obliquity) of the Earth’s axis and E refers to changes in the eccentricity of the orbit. P denotes precession, or changes in the direction of the axis tilt at a given point of the orbit. Taken from Solomon et al. (2007).
2 Obliquity refers to the tilt of the Earth’s rotational axis, with respect to the plane of its orbit around the Sun. 3 Precession refers to the oscillatory movement, around its axis, exhibited by a rotating body.
10 Key concepts of global climate change
However, the impact of these periodic changes in solar radiation is still unknown. In theory, changes in solar activity directly affect the climate by altering the amount of energy reaching the planet. Solar radiation also affects the concentrations of some greenhouse gases, such as stratospheric ozone.
Volcanic eruptions Catastrophic volcanic eruptions have the capacity to reduce global temperature. When an explosive volcanic eruption occurs, enor- mous quantities of ash, dust and sulfate aerosols are expelled into the stratosphere. These materials form a kind of natural barrier or shield that reflects solar radiation back to space before it reaches the planet’s surface, causing temperatures to decrease. However, this cooling effect is of short duration (2 to 3 years), as was the case after the eruptions of Mount Agung in Bali in 1963, Chichón Volcano in Mexico in 1983, and Mount Pinatubo in the Philippines in 1991.
Even the soot expelled by the burning oil wells in Kuwait appears to have reduced the amount of solar radiation reaching the Earth’s surface at that time. As a result, the planet’s temperature decreased slightly for a few months.
Human influence on climate Climate changes produced by humans are mainly the result of increases in concentrations of greenhouse gases in the atmosphere (Figure 3), and of changes in the amounts of aerosols (small par- ticles) that float in the atmosphere. These changes are capable of altering the planet’s energy balance and increasing or decreasing the temperature.
Greenhouse gases (GHG) Human activity results in the emission of several greenhouse gases
(GHG), the most important being carbon dioxide (CO2), methane
(CH4), nitrous oxide (N2O) and halocarbons (gases that contain fluorine, chlorine and bromine). The amount of GHG produced by
11 ABC of Climate Change in Mesoamerica
human activities increased by 70% between 1970 and 2004. Current
atmospheric concentrations of CO2, CH4 and N2O greatly exceed
pre-industrial values. In 2005, concentrations of CO2 and CH4 greatly exceeded the natural range over the last 650,000 years. Higher con- centrations of these gases in the atmosphere result in an increase in temperature.
Carbon dioxide is the most important greenhouse gas due to the enormous amounts of it released into the atmosphere. Since the start of the industrial revolution and the development of an economy
based on fossil fuels burning, and up to 1970, CO2 has increased by 100 ppmv (parts per million by volume). Between 1970 and 2004,
annual CO2 emissions increased by 80%. Approximately 75% of
the CO2 increase is attributed to the use of fossil fuels (mainly in
the transport sector) and to cement production. The remaining CO2 comes from deforestation and land use changes, which also release
CO2 and decrease the amount of this gas that could be sequestered by forests. The current rates of increase in carbon dioxide (along with those of nitrous oxide and methane) are unprecedented, at least in
the last 16,000 years. Current concentrations of CO2 in the atmo- sphere have reached 384 ppm (parts per million), and show no signs of decreasing or stabilizing (Figure 3). This value exceeds the range of the natural variability known in the last 650,000 years.
CH4 is the second most important greenhouse gas. It is released pri- marily as a result of anaerobic processes in agriculture, the production
of natural gas and waste treatment in landfills. Concentrations of CH4 in the atmosphere have risen from 715 ppm prior to the industrial
revolution, to 1774 ppm in 2005 (Figure 3). N2O is emitted due to fer- tilizer use and the burning of fossil fuels, although it is also released
through natural processes. Atmospheric N2O increased from 270 to 319 ppm between 1750 and 2005 (Figure 3). Finally, chlorofluorocar- bons (CFCs, a type of halocarbons) are completely synthetic gases introduced by humans, and do not occur naturally.
12 Key concepts of global climate change
Aerosols Aerosols are very small particles (between 0.07 and 20 μm, depend- ing on their origin) suspended in the atmosphere. Aerosols vary greatly in terms of their concentration, chemical composition and size, and may be of natural or anthropogenic origin. The burning of fossil fuels and biomass has increased the amount of sulfur aerosols, organic compounds and soot (also called “black carbon”) in the atmosphere. Mining and other industrial processes release additional amounts of aerosols and dust. In general, aerosols produce a cooling of earth’s temperature because they reflect solar radiation. For exam- ple, the accelerated industrial development after the Second World War increased atmospheric pollution in the Northern Hemisphere, contributing to a decrease in temperature between 1940 and 1970 approximately (Figures 4 and 6).
Figure 3. Concentrations of greenhouse gases in the last 2,000 years. Increases since 1750 are attributed to human activities during the industrial era. Concentration units are measured in parts per million (ppm) or parts per billion (ppb). Adapted from Solomon et al. (2007).
13 ABC of Climate Change in Mesoamerica
The unequivocal human action It is “very likely” (Annex 2 contains specific definitions regarding IPCC guidelines on uncertainty) that the increase in atmospheric greenhouse gases concentrations since the beginning of the indus- trial age (around 1750) has had a net warming effect on temperature. Numerous experiments have been carried out using different cli- mate models to determine the probable causes of climate changes that occurred in the 20th century. The results of these experiments show that natural forcings (solar radiation, aerosols from volcanic eruptions, etc.) are not sufficient to explain the trend toward ris- ing temperatures on Earth. These trends can only be replicated by including human influence in the models (Figure 4).
Furthermore, human influence considerably exceeds the intensity of any natural forcing that could otherwise control the climate (Figure 5). It is estimated that even if humans were to drastically reduce their greenhouse gas emissions, global warming would proceed more rap- idly than during the last 10,000 years. This is because the influence of greenhouse gases on the planet’s energy balance persists during a very
Figure 4. Changes in surface temperature (°C) relative to the 1901-1950 mean value, from one decade to another, from 1906 to 2005. The black line shows changes in observed temperatures y colored bands show the range covered by 90% of the simulations from recent models. The red band shows simulations that include natural and human factors, while the blue bands show simulations that include only natural factors. Adapted from Solomon et al. (2007).
14 Key concepts of global climate change
long time. In other words, there is sufficient scientific evidence to affirm that the global warming observed recently is the result of human action.
Figure 5. Main components of radiative forcing of climate change. Values represent the forcings in 2005 relative to the start of the industrial era (around 1750). Positive forcings lead to a warming of the climate and negative forcings to a cooling. Error bars represent the range of uncertainty for each forcing. Taken from Solomon et al. (2007).
15 ABC of Climate Change in Mesoamerica
Evidence of climate change The warming of oceans and of the land surface, changes in the dis- tribution and intensity of precipitation, rising sea levels, the melting of glaciers, the displacement of sea ice in the Arctic and the shrink- ing snow cover in the Northern Hemisphere are all signs that confirm the warming of the planet’s surface. However, the observed changes do not occur uniformly all over the world. For example, due to the influence of local factors, there are some areas of the world where the temperature has actually decreased, even though the global average is increasing. This is consistent with climate trends on a smaller spatial scale and is not sufficient to negate the warming at global level.
Temperature Between 1906 and 2005 global surface temperature of the Earth increased by 0.74 ºC (Figure 6a). Average temperatures in the Northern Hemisphere during the second half of the 20th century were likely the highest of the last 1,300 years. However, the increase has not been uniform around the world, neither in spatial nor in tem- poral terms. For example, warming has been greater over land than over the oceans, particularly since the 1970s. Seasonally, warming has been slightly greater in the winter hemisphere (also called the dark pole or pole in shadow) and in the high northern latitudes. However, in some parts of the world, such as the northern part of the North Atlantic, temperatures have decreased.
During the last century, warming occurred in two phases, with an accelerating rate in the last 25 years: between 1910 and 1940 the average global temperature increased by 0.35 ºC, and from the1970s it rose by 0.55 ºC (Figure 6a). Eleven of the 12 warmest years since records began have occurred since 1995. Consistent with this warm- ing, a decrease in the number of very cold days and nights has been observed. Furthermore, the duration of the ice-free season has increased in most middle and high latitude regions of both hemi- spheres. In the northern hemisphere, this translates into an earlier start to spring.
16 Key concepts of global climate change
Precipitation Precipitation shows greater spatial and temporal variability than temperature. Changes observed in some regions are dominated by long-term variations, though trends were not evident during the 20th century. During this same period, annual precipitation increased significantly in eastern parts of North and South America, northern
17 ABC of Climate Change in Mesoamerica
Europe and northern and central Asia. By contrast, the Sahel, the Mediterranean, southern Africa and parts of south Asia are now drier than at the start of the 20th century (Figure 7). In northern regions, precipitation in the form of rain is now more common that in the form of snow.
Changes in the oceans Warming has been most evident in parts of the middle and low lat- itudes, particularly in tropical oceans. Since 1961, the oceans have absorbed more than 80% of the heat added to the climate system. This has caused an increase in the average global temperature of the ocean to a depth of at least 3,000 m, with the consequent rise in sea level. Thermal expansion of seawater and the melting of ice, both processes due to the increased global temperatures, contribute
Figure 7. Changes in annual precipitation are not homogeneous around the world. In general, average precipitation during the 20th century increased in continents outside the tropics, but decreased in arid regions of Africa and South America. Yellow circles represent decreases in precipitation and green circles represent increases. The size of the circle represents the scale (%) of the change. Adapted from IPCC (2001).
18 Key concepts of global climate change
to rising sea levels. Thermal expansion has contributed 57% to the observed increase. Retreating glaciers, ice caps, and ice sheets are responsible for the remaining increase, at an annual rate of 1.2 ± 0.4 mm, between 1993 and 2003.
However, sea level has not risen uniformly around the world due to variations in the temperature changes in the oceans, the salinity of the water and oceanic circulation patterns. Sea level has gradually risen since the end of the nineteenth century, and it continues rising even more rapidly (Figure 6b). During the 20th century, the average rate of sea level increase was 1.7 mm per year. It is also likely that the rate of extreme sea levels has increased around the world since 1975.
Global sea level is projected to continue rising during the 21st century, and to do so at a faster rate than between 1961 and 2003. Thermal expansion is projected to contribute most heavily to average sea level increases for the next 100 years, at least, particularly if green- house gas concentrations are not stabilized.
Ice and snow cover In the northern Hemisphere, springtime snow cover has been declin- ing by 2% per decade since 1966 (Figure 6c). Furthermore, the snow is melting earlier in spring. There has been a widespread decline in mountain glaciers and snow cover in both hemispheres, while annual Artic sea ice extent has been shrinking at an average rate of almost 3% per decade. The decrease in the area of sea ice exceeds 7% per decade. The area of permafrost and seasonally frozen ground, as well as the ice in rivers and lakes, has also decreased.
Extreme events “Extreme events” refer to maximum or minimum values of a par- ticular variable, or to infrequent climatic events of great intensity (for example, storms, droughts, heat waves). In the last 50 years, the number of cold nights has decreased and the number of warm nights has increased. Maximum and minimum temperatures have also
19 ABC of Climate Change in Mesoamerica
increased (Figure 8). The number of frost-free days has increased as the temperature has risen in middle latitudes. It is likely that heat waves are now more frequent in most land areas.
It is to be expected that a warmer climate will increase the risk of drought in places where it does not rain, and increase the risk of flooding in areas where it does rain. The distribution and timing of droughts and floods is most profoundly affected by the cycle of El Niño events, particularly in the tropics and in many parts of the mid- latitudes of the Pacific Rim countries.
The intensity of precipitation and the risks of intense rainfall and snowfall increased during the 20th century due to an approximate 5% increase in atmospheric water vapor. As a result, during the last 50 years more intense precipitations have been observed in warm cli- mates, even in places where overall annual precipitation is decreasing.
Figure 8. Trends observed (in days per decade) from 1951 to 2003 in the frequency of extreme temperatures, relative to mean values for period between 1961 and 1990: a) cold nights, b) cold days, c) warm nights and d) warm days. The red line shows the decadal variations. Adapted from Alexander et al. (2006).
20 Key concepts of global climate change
This means that the seasonality of rainfall is now more marked. Very dry land areas across the globe have more than doubled in extent since the 1970s, and droughts have become more common in many regions of the planet.
It is also very likely that even stronger events will occur as overall levels of precipitation increase. The number of category 4 and 5 hur- ricanes has increased by about 75% since 1970. The largest increases have been observed in the North Pacific, Indian and Southwest Pacific Oceans. In the North Atlantic, the number of hurricanes was also above average in 9 of the 11 years during the period from 1996 to 2007. However, the detection of long-term trends in cyclonic activ- ity is not yet very reliable.
Projections of future climate change have a certain level of uncer- tainty due to the changing nature of the climate and to the difficulty in determining future levels of GHG emissions. Concentrations of GHG depend on many assumptions and factors with varying degrees of uncertainty, such as population growth, development and use of alternative energies, technological and economic development, and human policies and attitudes toward the environment. For these rea- sons, the different scenarios used contemplate different ranges of these factors to investigate the potential consequences of anthropo- genic climate change.
A climate scenario is defined as a plausible and generally simplified representation of a possible future climate, based on an under- standing of how the climate works and of the different factors that influence it. Scenarios are typically constructed as input to evalu- ate the possible impacts of climate change on natural and social systems.
21 ABC of Climate Change in Mesoamerica
IPCC carbon emissions scenarios The IPCC Special Report on Emissions Scenarios (SRES; see IPCC, 2000) contains 40 different scenarios, grouped into four families (Table 1) that explore alternative forms of development. The sce- narios incorporate demographic, social, economic, technological, and environmental factors, together with the resulting greenhouse gas emissions, to draw some conclusions about future climate change. The main rationale behind these scenarios is that societies have the option of either working together to resolve global problems through joint and comprehensive solutions, or remaining isolated and trying to resolve their problems independently. Furthermore, development goals may be aimed at increasing human wealth or at conserving the environment (Figure 9).
Figure 9. Conceptual framework of IPCC families of climate change scenarios. The horizontal axis represents ways of adapting to problems while the vertical axis represents the type of development. Adapted from Palma Grayeb et al. (2007) and Anderson et al. (2008).
22 Key concepts of global climate change
Table 1. Characteristics of IPCC families of climate change scenarios.
Number of Family Characteristics scenarios
Rapid economic growth, low rate of population growth, and rapid shift towards more efficient technologies . Convergence between regions . Differences in personal income significantly A1 17 reduced . This family is divided into three groups based on the energy system used: intensive use use of fossil fuels (A1F), use of non-fossil fuels (A1T), and balance between different sources (A1B) .
A very heterogeneous, self-sufficient world that maintains local identities . Population growth rates converge slowly, which results in high A2 6 population growth . Per capita economic growth is slower and more fragmented than in other families .
A convergent world, with low population growth and rapid changes in economic structures . Shift toward an economy based on services and information technology . Less intensive use B1 9 of materials, introduction of cleaner and more efficient technologies. Emphasis on global solutions to promote environmental, economic and social sustainability and greater equity .
A world emphasizing local solutions to environmental, social, and economic sustainability . Population growth and economic development are moderate . Technological B2 8 change is less rapid but more diverse than in B1 and A1 . This family focuses on environmental protection and social equity, but at the regional and local levels .
Source: IPCC (2000) .
23 ABC of Climate Change in Mesoamerica
Other than those already existing, IPCC scenarios do not explicitly contemplate climate policies that focus directly on reducing green-
house gas emissions and maximizing the size of CO2 sinks. Instead, the idea is that the scenarios will serve as a reference for analyzing the potential consequences of implementing additional policies. All scenarios are considered equally valid and likely. This leaves the door open so political discussions regarding possible courses of action in response to climate change can take place.
The importance of considering several scenarios Comparing groups of similar models, or making comparisons between models with different structures, is useful to quantify the probabilistic aspect of the scenarios. It is also necessary to construct various future climate scenarios to quantify the uncertainty of the estimates. In terms of policies, instead of deciding whether a specific model is most representative of certain future conditions, consider- ing several models enables us to expand our options for developing a broader range of adaptation alternatives. For this reason, the IPCC recommends that at least two families of scenarios –with a wide variety of assumptions– be considered in any analysis of climate change. In the last simulations of global climate change car- ried out for IPCC the B1, A1B and A2 scenarios were used. These are interpreted as possible “low”, “medium” and “high” levels of emissions. In the Mesoamerican region, the A2 and B2 scenarios are most commonly used.
Projections of future climate change If current climate change mitigation policies and sustainable devel- opment practices are maintained, greenhouse gas emissions will continue to increase in the coming decades. As a result, global warming will intensify during the 21st century, with climate changes very likely greater than those experienced in the 20th century. The warming projected for the 21st century would have a geographic dis- tribution similar to that observed until now.
24 Key concepts of global climate change
According to IPCC projections, the global average temperature increase observed between 1990 and 2005 (0.15 and 0.30 ºC per decade) will remain approximately the same during the next 20 years. This trend would not change even if concentrations of all greenhouse gases and aerosols were to remain at constant levels similar to those of 2000. Despite the fact that the exact ranges of temperature change vary slightly between climate scenarios, all IPCC scenarios show temperature increases (Table 2); up to 6 ºC in the most extreme esti- mate. It is very unlikely that the temperature increase will be less than 1.5 ºC.
The extent of the area covered with snow and sea ice will continue to shrink. It is very likely that extreme temperatures, heat waves and intense precipitations will become more frequent. It is likely that future tropical cyclones will be more intense due to higher sea surface temperature. Trajectories of extra-tropical storms are pro- jected to shift toward the poles. It is very likely that precipitation will increase in high latitudes, while decreasing by up to 20% in subtropi- cal regions.
Past and future anthropogenic carbon dioxide emissions will con- tinue to contribute to warming and sea level rises for more than a millennium. Even if all radiative forcings are stabilized and main- tained constant by 2100, we would still expect to see an increase of about 0.5 ºC in global average temperature up to 2200. Thermal expansion of the oceans would continue for many centuries, due to the time required to transport heat down to the deepest layers of the ocean. Sea level rise is projected to reach 0.3 to 0.8 m, relative to the 1980–1990 level, towards the year 2300 (see Table 2 for estimates up to 2100). If the Greenland Ice Sheet were to disappear, sea level would increase by up to 7 m. This value is similar to the sea level esti- mated for the last interglacial period, some 125,000 years ago.
25 ABC of Climate Change in Mesoamerica
Table 2. Average range of temperature (ºC) and sea level (m) increase for the main IPPC climate scenarios.
Temperature Case Sea level rise Increase*
Constant GHG concentrations 0 .3 – 0 .9 Not available Year 2000
Scenario B1 1 .1 – 2 .9 0 .18 – 0 .38
Scenario A1T 1 .4 – 3 .8 0 .20 – 0 .45
Scenario B2 1 .4 – 3 .8 0 .20 – 0 .43
Scenario A1B 1 .7 – 4 .4 0 .21 – 0 .48
Scenario A2 2 .0 – 5 .4 0 .23 – 0 .51
Scenario A1FI 2 .4 – 6 .4 0 .26 – 0 .59
* Likely temperature and sea level increases for 2090-2099 relative to 1980-1999 . Adapted from IPCC (2007) .
Areas of uncertainty in the predictions Although our knowledge of the global climate system continues to expand rapidly and significantly, there are still uncertainties4� regard- ing some of the observed climate changes. These uncertainties do not necessarily negate or invalidate the predictions made. It is simply that there are certain areas of scientific knowledge in which the driv- ing mechanisms are not fully understood. Some of the main areas of uncertainty are mentioned below.
Analyzing and monitoring observed changes in extreme events (droughts, hurricanes, frequency and intensity of precipitation, etc.) is more complex than with average climate patterns, since these require longer time series and a range of spatial and temporal scales. The adaptive capacity of some natural and human systems also makes it difficult to detect the effects of climate change and its driv- ing forces.
4 See Annex 2 for a description of the IPCC’s treatment of uncertainty.
26 Key concepts of global climate change
Although most of the climate change models currently used are consistent in their simulations of global-level patterns, there are still difficulties in simulating certain changes (such as precipitation) at regional levels. At these smaller scales, changes in land use or specific pollution problems make it more complicated to detect the effects of anthropogenic warming on natural systems.
The intensity of climate feedback processes such as ocean heat uptake, the role played by clouds and the carbon cycle have yet to be quantified with greater certainty. Similarly, the full impacts of aero- sols on cloud and precipitation dynamics remain uncertain. The scale of future sea level rise is still unknown (especially its upper limit) due to uncertainty surrounding estimates of ice-sheet loss in Greenland and the Arctic, and the process of heat distribution in the oceans.
Climate in Mesoamerica
2 Climate in Mesoamerica
Historical climate patterns
In Mesoamerica, precipitation and temperature exhibit well-defined annual patterns, modified periodically by fluctuations in the temper- ature of the surrounding oceans and by the El Niño/La Niña cycles, the Pacific Decadal Oscillation (PDO). In general, the interactions between the trade winds from the east and the region’s orographic complexity determine the differentiated precipitation patterns of the region’s Caribbean (windward) and Pacific (leeward) slopes. The effects of the “rain shadow” created by the mountain systems gener- ally mean that the Caribbean slope is rainy practically all year round, while the Pacific slope is characterized by a prolonged dry season (Figure 10, compare stations of Limón and Puerto Lempira on the Atlantic vs. La Unión and Liberia on the Pacific). The southern part of Central America is rainier than the north.
Precipitation On the Pacific side of Mesoamerica, precipitation is characterized by a prolonged dry season lasting approximately from November until April or May, and a wet season during the rest of the year. The increased intensity of the trade winds in July produces a peak of pre- cipitation in most parts of the Caribbean slope of Central America and southern Mexico (Figure 10). Due to prevailing trade winds from the east in the region, any rise in the surface temperature of the ocean east of the isthmus causes an increase in precipitation. In contrast, when the temperature of the ocean’s surface decreases, pre- cipitation declines by up to 40% during the months of July/August
29 ABC of Climate Change in Mesoamerica
(during the mid-summer dry period commonly known as veranillo or canícula) in the Pacific slope (see the Liberia and Palmar Sur stations in Figure 10). The veranillo is more pronounced on the western side of Central America, in the Yucatán Peninsula, and in eastern Mexico. However, this phenomenon is practically absent in western Mexico, southern Belize, the south east of Honduras, eastern Nicaragua and Costa Rica, and the north east of Panama.
Severe droughts on the Pacific coast are associated with the El Niño phenomenon (an increase in the surface seawater temperature of the equatorial Pacific that generates anomalies in the planet’s atmo- spheric circulation). At the same time, masses of cold air from North America during the winter months, and the trade winds between July and August, produce intense rains that cause flooding on Central
Figure 10. Topography and monthly precipitation for selected meteorological stations (location shown with “+”) in Central America and southern Mexico. Inset graphs show monthly precipitation (vertical bars) for each station. Taken from Magaña et al. (1999).
30 Climate in Mesoamerica
America’s Caribbean slope. The regions most affected by these con- ditions are the northern coast of Honduras and the eastern coasts of Nicaragua, Costa Rica and Panama. The northern coast of Honduras and Belize are the areas most susceptible to the direct impact of hurricanes, although the coast of Nicaragua has also suffered their effects in recent decades.
Temperature Temperature is strongly related to the temperatures of the Pacific Ocean, including patterns linked to El Niño events. The tempera- ture regimen is also closely related to the annual precipitation cycle. Daily temperatures reach their maximum value before the start of the rainy season and fall around January. Minimum temperatures show a different pattern: the highest values are observed in July (when increased cloud cover decreases radiative cooling) and the lowest values during the Northern Hemisphere winter.
Changes observed in climate variables
Central America is considered to be the main “hot spot” for climate change in the tropics (Figure 11). An analysis of temperature and precipitation data from 105 meteorological stations located through- out the Mesoamerican region and in the northern part of South America (Aguilar et al., 2005) show many changes in the extreme values of these variables during the last 40 years.
On a regional scale, temperature indices showed significant varia- tions throughout the region during the period between 1961 and 2003 (Table 3). The annual percentage of warm days and nights increased by 2.5% and 1.7% per decade, respectively. At the same time, the number of cold nights and cold days decreased by -2.2 and -2.4% per decade (Table 3). Temperature extremes increased by between 0.2 and 0.3 ºC per decade. The duration of the periods of consecutive cold days also decreased.
31 ABC of Climate Change in Mesoamerica
Figure 11. The Regional Climate Change Index (RCCI) for 26 land regions of the world, calculated on the basis of 20 General Circulation Models and 3 IPCC emission scenarios. The size of the circles represents the scale of the changes in temperature and precipitation indices. Taken from Giorgi (2006).
During the last 45 years, no decrease in annual precipitation has been observed in the region, though there has been a slight increase in its intensity. Furthermore, the number of consecutive dry days has increased. In other words, precipitation patterns have changed so that now it rains during a shorter period of time, but does so more intensely, with obvious impacts on agricultural production, soil con- servation, floods, water availability, etc.
While most of the meteorological stations analyzed show positive trends (increased precipitation), overall average annual precipitation in the region and the number of consecutive wet days do not show significant changes (Table 3). This is probably due to the limited time periods covered by the data series and to major annual variations in precipitation. Furthermore, the heterogeneity of the precipitation patterns throughout the region (Figure 12) makes it difficult to iden- tify a clear trend for the area as a whole. For example, the number of
32 Climate in Mesoamerica
Table 3. Trends in regional temperature and precipitation indices for the period 1961-2003.
Trend Index Units (units/decade) Temperature Warm days % of days 2.5 Warm nights % of days 1.7 Cold days % of days -2.2 Cold nights % of days -2.4 Daily temperature range ºC 0.1 Highest maximum temperature ºC 0.3 Lowest maximum temperature ºC 0.3 Highest minimum temperature ºC 0.2 Lowest minimum temperature ºC 0.3 Duration of cold period number of days -2.2 Duration of hot period number of days 0 .6 Precipitation Total annual precipitation mm 8 .7 Simple index of daily intensity mm 0.3 Very wet days mm 18.1 Extremely wet days mm 10.3 Maximum precipitation in 1 day mm 2.6 Maximum precipitation in 5 days mm 3 .5 Days of strong precipitation number of days -0 .1 Days of very strong precipitation number of days 0 .1 Consecutive dry days number of days 0 .4 Consecutive wet days number of days -0 .1
Values in bold are statistically significant at 5%. Adapted from Aguilar et al . (2005) .
33 ABC of Climate Change in Mesoamerica
consecutive dry days decreased in central and southern parts of the region, but increased in northern Mexico and the Caribbean.
However, extreme precipitation indices have increased significantly (Table 3) and are strongly and positively correlated with the tem- perature of the tropical Atlantic Ocean. The latter indicates that prolonged rainy seasons are related to the warm waters in that oce- anic basin.
The trend over the last 40 years suggests a strengthening of the hydrological cycle throughout the region, with more rain produced by extreme events and greater average precipitation per episode. This trend is expected to continue in the future, possibly resulting
Figure 12. Temporal trends in (a) the percentage of warm days, (b) the percentage of cold days and (c) total annual precipitation for the period 1971- 2003. Red triangles (with the upward pointing apex) represent an increase, and blue triangles (with the downward pointing apex) represent a decrease in the variable. The large triangles represent statistically significant trends, while the small triangles represent non-significant trends. Adapted from Aguilar et al. (2005).
34 Climate in Mesoamerica
in a greater frequency or intensity of extreme events (floods and/ or droughts). This does not appear to be linked to El Niño. Despite the fact that recent hurricanes have caused extensive damage in the region, it has not been possible to determine with any certainty whether in future these will become more frequent and intense in the Caribbean.
Climate scenarios for Mesoamerica
The most recent climate scenarios for the region use data generated by the Worldclim�5 project (Hijmans et al., 2005). These scenarios complement the work carried out in the region since the 1990s. Most of the recent climate models for the isthmus underestimate the amount of precipitation in Central America (by up to 60%), but con- sistently replicate the seasonality of the region’s climate, including the veranillo (Rausher et al., 2008).
Although IPCC models consider a wide range of very complex inter- actions between aquatic, terrestrial, and atmospheric components, and their capacity to replicate climate conditions is recognized, their resolution is not the most appropriate for evaluating the effects at the regional or country level. For this, it is necessary to reduce the scale (through a process known as “downscaling”) and increase the resolution of the data (STARDEX, 2009; Figure 13). The reference period for climate data is 1961–1990. Changes in temperature and precipitation were calculated for the time horizons of 2020, 2050 and 2080. These horizons are generic names for the periods 2011–2040, 2041–2060 and 2061–2090, respectively. IPCC B2 and A2 scenarios (Table 1) were selected as examples of a “favorable” scenario and an “unfavorable” scenario, respectively. In addition, a “Climate Change Severity Index” (CCSI) was developed, details of which are included in the section on effects of climate change in this document.
5 http://www.worldclim.org. Last visit 10/23/2010.
35 ABC of Climate Change in Mesoamerica
Figure 13. “Downscaling” and increase of the spatial resolution (from 400 km to 12 km) for a temperature change model for Mesoamerica. Adapted from Anderson et al. (2008).
Expected changes in temperature and precipitation
The global average surface temperature of the planet is expected to increase between 1.4 and 5.8 ºC up to 2100. Consistent with this change, temperatures are expected to rise throughout the Mesoamerican region. However, predictions differ regarding the scale, direction (increase or reduction) and location of the changes in precipitation. Despite this uncertainty, in general, the number of dry days is expected to increase, along with the frequency of more intense precipitations and extreme events such as storms and floods. Future climate changes may possibly be due to changes in the sur- face temperature of the ocean, the displacement of the inter-tropical convergence zone, the expansion and intensification of the high pres- sure zones in the north Atlantic, and greater temperature contrasts between the continental mass and the ocean.
36 Climate in Mesoamerica
The models project a regional increase of 1 to 2 ºC for 2011. Other models predict that the temperature would be between 2 and 4 ºC higher in 2080 (for scenarios B2 and A2, respectively). In general, an overall increase in temperature is projected throughout the region, with the extreme north of the region being affected by a greater temperature increase than the extreme south. Toward 2080, for sce- nario A2, the temperature could rise by as much as 6.5 ºC in the far north of Mesoamerica, in areas around Belize, Peten, and the border between Guatemala and Mexico. In the most favorable scenario, the temperature of that same area would rise by 4 ºC for 2080. The area to the south of the Nicaraguan-Costa Rican border would experi- ence a temperature increase of less than 2 ºC under both scenarios (Figure 14). The rest of the region would experience gradual changes between these geographic extremes.
Precipitation projections are more heterogeneous, both in spatial and temporal terms. In general, the greater portion of the Mesoamerican region, especially the Pacific coast, will experience a decrease in precip- itation toward 2020. Under the favorable scenario, the exceptions are the southwest coast of Guatemala and the far south of Panama, where there would be a slight increase in precipitation—but only under the favorable scenario. By contrast, under the unfavorable scenario, pre- cipitation in the northeast coast of Honduras, all of Nicaragua, most of Costa Rica and the central and northern portion of Panama would decline by at least 20% (Figure 14, Table 4). The rest of the region would also experience decreased precipitation under this last scenario, although not as severe as the other areas mentioned. Other models (Rausher et al. 2008) predict greater reductions in precipitation in southern Guatemala, El Salvador, Honduras and western Nicaragua.
With regard to the spatial distribution of precipitation in the future, there are differences between the recent models. For example, simu- lations done by SICA et al. (2006) and the results of PRECIS6, show
6 http://precis.insmet.cu/eng/Precis-Caribbean.htm and http://precis.insmet.cu/ eng/datos.html. Last visit 10/23/2010.
37 ABC of Climate Change in Mesoamerica
Figure 14. Changes in temperature and precipitation for Mesoamerica. Anomalies in average annual temperatures (ºC) to 2080 for (a) the B2 scenario and (b) the A2 scenario, and anomalies in average annual precipitation (%) to 2020 for (c) the B2 scenario and (d) the A2 scenario. The colored vertical bars show the magnitude of change in ºC (a and b) and % (c and d). Adapted from Anderson et al. (2008).
different precipitation trends for the northern and southern parts of the region. In these simulations, Costa Rica appears as a transition region. To the south of 7º latitude, an increase of approximately 2% in precipitation is estimated, while to the north of that latitude a 12% decrease in precipitation is estimated up to 2100. The latter models
38 Climate in Mesoamerica
coincide with those described by Anderson et al. (2008) with regard to temperature. In addition, all the models analyzed coincide in pre- dicting decreased precipitation during the rainy season.
Table 4. Changes in temperature (ºC) and precipitation (%) for Central America, for three time horizons. Ranges come from seven global circulation models and the four families of IPCC scenarios.
Year Variable Season 2020 2050 2080
Temperature (ºC) Dry +0 .4 to +1 .1 +1 .0 to +3 .0 +1 .0 to +5 .0
Rainy +0 .5 to +1 .7 +1 .0 to +4 .0 +1 .3 to +6 .6
Precipitation (%) Dry -7 to +7 -12 to +5 -20 to +8
Rainy -10 to +4 -15 to +3 -30 to +5
Source: Magrin et al . (2007) .
Effects of climate change on Mesoamerica
3 Effects of climate change on Mesoamerica
According to the IPCC, the societies and natural systems of the Mesoamerican region are highly vulnerable to extreme climate events. This is due to a combination of geographic reasons (con- fluence of several ocean currents and effects of periodic climatic oscillations such as El Niño/La Niña), and economic and social fac- tors (low levels of social development, inequality in the distribution of wealth, low capacity for adaptation).
The poorest communities are generally the most vulnerable; the most affected are the most exposed. Around 54% of the population living in poverty has a higher probability of suffering the adverse effects of climate change7. Part of this vulnerability is due to the pres- ence of populations in areas affected by hurricanes, unstable lands, or in settlements on land prone to flooding. The region’s vulnerabil- ity to climate events is also exacerbated by the interactions between demographic pressure, lack of planning for urban growth, poverty and rural migration, limited investment in infrastructure and ser- vices, overexploitation of natural resources, pollution and problems with inter-sectoral coordination.
Moreover, if a certain percentage of the region’s population lives in extreme poverty, with their livelihoods based on natural resources that are threatened by climate change, this part of the population is more susceptible to suffering the adverse effects of climate change and of becoming even poorer. In fact, climate change is already
7 http://www.alamys.org/default.asp?id=283&posicion1=4322. Last visit 10/23/2010.
41 ABC of Climate Change in Mesoamerica
compromising efforts to meet the commitments of the Millennium Development Goals (see Manzanares et al. 2008).
The IPCC points out that changes in climate seasonality or annual events have the potential to severely affect different sectors: water resources and their management, terrestrial ecosystems, agriculture, fibers and forest products, coastal systems, coral reefs and wetlands, industries, health and society in general (Table 5). Many of these sectors are closely linked together and climate change would pro- duce simultaneous and synergistic effects among them. Furthermore, the influence of human land and water use patterns are factors that could place certain ecosystems at greater risk, or could improve the survival of others.
In Mesoamerica, it is believed that most of the direct and indirect effects of climate change will revolve around water availability. Water scarcity has numerous repercussions: on biodiversity, on coun- tries’ capacity to generate hydroelectric power, on the availability of potable water, on the population’s health levels, on agricultural production, etc. The sectors most affected by climate change are bio- diversity, agriculture and human health.
The following section contains a general description of the potential effects of climate change on different sectors in the region, offer- ing local examples when possible. The main effects by country are detailed in Annex 1. Given the scarcity of scientific and socioeco- nomic studies on observed and expected changes to natural and human systems in Mesoamerican countries, some of the effects men- tioned are generalized from effects expected in other regions. Due to the diversity of sectors and processes involved, this is not an exhaus- tive review of all the possible effects of climate change.
42 Effects of climate change on Mesoamerica
Table 5. Expected climate change and its possible effects
Expected changes Projected effects ▲ Mortality and serious diseases in elderly Higher maximum people and in the rural population temperatures ▲ Thermal stress in cattle and in wild plants and animals More hot days ▲ Risk of damage to crops ▲ Demand for electric refrigeration More heat waves ▼ Reliability in energy supply Higher minimum ▲ Distribution and activity of pest and disease temperatures vectors ▼ Human morbidity and birth rates related to Fewer cool days the cold ▼ Risk of damage to crops Fewer frosts ▼ Demand for caloric energy ▲ Damage caused by floods and landslides ▲ Soil erosion More intense ▲ Recharge of aquifers on some floodplains precipitation ▲ Pressure on relief systems in the event of disasters ▲ Damage to buildings due to soil contraction ▲ Risk of forest fires Greater risk of drought ▼ Quality and quantity of water resources ▼ Crop yields Increased intensity of ▲ Risk to human life hurricanes ▲ Coastal erosion ▲ Risk of infectious disease epidemics Increase in average ▲ Damage to coastal infrastructure and maximum ▲ Damage to coastal ecosystems (mangroves precipitation events and reefs) Intensification of ▼ Hydroelectric energy generation potential (in droughts and flooding drought zones) associated with El Niño ▼ Agricultural and pasture productivity
▲: increase ▼: reduction Source: Adapted from SERMANAT & UNEP (2006), using IPCC data .
43 ABC of Climate Change in Mesoamerica
Climate change has not only affected normal precipitation patterns, but has also affected the periodicity, intensity and duration of various climatic phenomena. Both an excess and a lack of water affect the quantity and quality of water available for natural ecosystems and human consumption. Greater precipitation produces an increase in water flows and sediment runoff, creating problems with the quality of potable water and the functioning of coastal-marine ecosystems. It also increases the risk of flooding, with consequent effects on human infrastructure, agriculture, livestock production, and health.
By contrast, a decrease in precipitation reduces the quantity of water available in a watershed, a process that is exacerbated by the nega- tive interaction with higher temperatures. In general, vulnerability to water scarcity is greater in regions that are typically drier and warmer. These vulnerabilities will also increase due to the negative interaction between increased demand for water for domestic use and irrigation (due to population growth), and the more arid condi- tions that are expected in many watersheds. The problem of water scarcity will be further complicated in cases where land settlement patters do not coincide with the distribution of this resource.
According to the IPCC, accelerated urban growth, increased poverty and lower investment in water supply systems will contribute, among other things, to water shortages in many cities, a high percentage of the population with no access to sanitation services, a lack of water treatment plants, the absence of urban drainage systems and high levels of groundwater pollution. In the Central Valley of Costa Rica, for example, an imbalance in the potable water supply is expected by 2022, due to a combination of climate change and an extra 1.1 million people. In Mexico, per capita water availability will fall sharply from 11,500 m3/inhabitant/year in 1955 to 3,500 m3/inhabitant/year in 2025, due to economic development and demographic growth.
44 Effects of climate change on Mesoamerica
Serious problems are also expected with the water supply for human use on the plains, the Motagua Valley and the Pacific coast of Guatemala; in El Salvador; in the Central Valley and Pacific coast of Costa Rica; in the intermountain regions of northern, central and western Honduras; and in the Azuero Peninsula in Panama. The reduction in water availability will also affect capacity for hydroelec- tric energy generation in Belize, Honduras, Costa Rica and Panama.
In severe drought conditions, unsound agricultural practices (defor- estation, soil erosion, and excessive pesticide use) will also degrade the quality and quantity of surface and ground water. This would occur in areas that are currently degraded such as León, the Sebaco Valley, Matagalpa and Jinotega in Nicaragua; the metropolitan and rural areas of Costa Rica; and other areas in Central America.
According to the IPCC, it is very unlikely that all the changes observed in many natural systems are solely due to their natural variability. Instead, it is likely that global warming due to human activity over the last 30 years has had a discernible influence on various natural systems. However, it is still not possible to unequivocally attribute all the responses observed in natural systems to anthropogenic global warming. For example, the natural variability of temperature is greater on smaller scales, which makes assigning a specific response to global temperature patterns difficult. Moreover, on a small scale, non-climatic factors such as changes in land use or the presence of invasive species also influence the functioning of ecosystems.
Mesoamerica possesses approximately 9% of the world’s biologi- cal diversity. The importance of this wealth is undeniable, given that it plays a major role in supplying goods and services that are essential for human survival: food, fibers, fuels and energy, pas- tures, medicines, water and air quality, flood control, pollination, soil
45 ABC of Climate Change in Mesoamerica
formation, nutrient cycle regulation, and cultural, spiritual, aesthetic and recreational values, among others. In general terms, climate change—accentuated by forest fragmentation and deforestation— is expected to affect all aspects of biodiversity. The most important effects will include an increased rate of species extinction and the displacement of habitats to higher latitudes and elevations.
In Mesoamerica, changes in the seasonality and intensity of precipi- tation (more than annual changes in temperature) will lead to the replacement of rainy and wet climate zones with dry and very dry zones. Montane and dry forests will be most vulnerable to this pro- cess. For example, in central and southern Mexico tropical forests are expected to be replaced by savannahs, and semi-arid vegetation by arid vegetation in most of central and northern Mexico. Similarly, in Nicaragua and Costa Rica there is a very marked trend toward an increase in very dry zones, to the detriment of wet zones (Figure 15). The complete displacement, or possible replacement, of certain types of ecosystems would cause serious impacts to the diversity of plants and animals, many of them already endangered (Table 6), as well as to the environmental services currently provided by forests. Not even protected areas, with their high diversity and vulnerability, would be totally immune to these changes.
Species with high adaptive capacity and rapid dispersal (birds, mam- mals, some insects) could move to new areas with suitable climates. However, in the case of montane forests, for example, the possibil- ity of species relocating to more favorable conditions is practically non-existent because the peaks of the mountain ranges constitute the maximum physical limit where the species could migrate to and subsist. Even in lowland forests, the longevity of some tree species and the constraints imposed by their dispersal systems and growth habits would make it difficult for them to migrate to new areas with climates suitable for their development.
46 Effects of climate change on Mesoamerica
Biological productivity is another important aspect of biodiversity that is affected by climate change. These changes can affect goods and services essential for humanity (production of foods, fibers, tim- ber, etc.), as well as the way in which the carbon cycle functions on
Figure 15. A) Map of existing life zones in Costa Rica and B) Map of potential life zones in Costa Rica by 2020 under a B2 scenario. Taken from Jiménez (2009).
47 ABC of Climate Change in Mesoamerica
land and in the oceans, and the number and types of organisms in the ecosystems. Changes in or losses of certain organisms from an ecosystem could also cause losses in net productivity. In the case of forests, this could translate into a reduction in the timber supply (at a time when demand continues to rise), which would also lead to greater pressure on remnant forests.
Climate change severity index The climate change severity index (CCSI) measures the magnitude of climate change in a particular place, relative to the natural climate variations historically experienced in that place. Data for calculating
Table 6. Number of known mammal, bird and higher plant species that are endangered in Mesoamerica.
Mammals Birds Higher plants
Country Known Known Known species species species species species species Threatened Threatened Threatened
Belize 125 4 161 2 2894 28
Costa Rica 205 14 279 13 12119 109
El Salvador 135 2 141 0 2911 23
Guatemala 250 6 221 6 8681 77
Honduras 173 10 232 5 5680 108
Mexico 491 70 440 39 26071 --
Nicaragua 200 6 215 5 7590 39
Panama 218 20 302 16 9915 193
Source: UNDP et al . (2003) .
48 Effects of climate change on Mesoamerica
the CCSI came from Worldclim. Although the CCSI has been calcu- lated for three different climate models (Anderson et al., 2008), the results given here only describe outcomes for the A2 and B2 scenar- ios calculated with the HADCM3 model only. It is important to bear in mind that similar calculations using other models can produce dif- ferent results.
Under the B2 scenario for 2050, the CCSI suggests few significant impacts; these are concentrated mainly toward the east coast of Nicaragua and the southern end of Panama. By contrast, under the A2 scenario for 2050, practically all of Mesoamerica would expe- rience significant changes in its climate conditions (see red area in Figure 16). Climate change severity would be greatest on the Caribbean coast of Costa Rica and Panama (black area in Figure 16). The differences between the two scenarios underscore the impor- tance of implementing mitigation efforts, in order to reduce the possible impacts of climate change.
All the ecosystems of Mesoamerica will be affected to a greater or lesser degree by climate change. In the A2 scenario, at least 25% of the area with broadleaf forests, coniferous forests, mangroves, mixed forests, scrub forests, wetlands and agriculture will experience immi- nent significant changes. The CCSI indicates that approximately 15% of the area covered by broadleaf forests and agriculture and between 5 and 10% of the area with savannahs and mangroves would expe- rience climate changes outside the range of their natural historic variability.
Terrestrial ecosystems As in the case of the Amazon, Central America’s forests are at high risk of having their area reduced due to increases in temperature. Forests will likely be replaced by savannahs, which are ecosystems that are more resistant to the multiple influences caused by increased temperatures, droughts and fires. Although fire could become a more common modifying element of Central American ecosystems, it is
49 ABC of Climate Change in Mesoamerica
Climate Change Severity Index
Low severity Approximate areas of land in each category (1000 km2) Approaching significant changes
Significant changes vary during year
Pushing comfort zone limits
Outside comfort zone
Far outside comfort zone
Climate Change Severity Index
Low severity Approximate areas of land in each category (1000 km2) Approaching significant changes
Significant changes vary during year
Pushing comfort zone limits
Outside comfort zone
Far outside comfort zone
Data Derived from: Wordclim Climate Grids: Current and Future Conditions (HADCM3 A2 & B2) 2008.
Figure 16. Climate change severity index for Mesoamerica in 2050, for the B2 scenario (a) and the A2 scenario (b). The bar graphs in the boxes show the land area in each category of severity. Adapted from Anderson et al. (2008).
50 Effects of climate change on Mesoamerica
not expected to be a determinant factor in the disappearance of forests. The future incidence of fires and their influence on the eco- systems is an aspect that has not been well studied in Mesoamerica.
In moist lowland forests, there is documentation showing that productivity falls and mortality increases during years when high temperatures and low precipitation prevail. On the other hand, research in Brazil indicates that the dynamism (higher growth, higher mortality, increase in species adapted to perturbed areas) of moist forests appears to be increasing, possibly due to the increase in atmospheric CO2 and climate changes. Therefore, Mesoamerican forests can be expected to respond similarly.
The height of the cloud layer during the dry season has been rising at a rate of 2 m per year, due in part to deforestation. If this increase continues and the temperature also increases 1 or 2 ºC in the next 50 years, the montane cloud forests will be threatened. In locations at lower elevations or on isolated peaks, some species of plants and ani- mals could go extinct because the range of elevation would not allow them to adapt naturally to the temperature increases. This could have severe negative impacts on species diversity and composition. For example, in Monteverde, Costa Rica, fewer cloudy days have already been strongly associated with a 40% reduction in amphibian populations. It is also known that lower relative humidity causes the death of epiphytes and other plants.
Populations of amphibians (mainly frogs and toads) are being affected in the cloud forests after years of low precipitation. Moreover, links have been found between higher temperatures and frog extinctions caused by pathogens. In Costa Rica, the extinction of the golden toad (Bufo periglenes) is attributed in part to an increase in the temper- ature of its habitat, which fosters the proliferation of a cutaneous fungus. Temperature changes would affect the migration patterns of certain species and alter the phenology (biological events such as flowering and fruiting of plants, reproductive seasons) of others.
51 ABC of Climate Change in Mesoamerica
For example, the ranges of elevation of some tropical forest birds of Costa Rica have expanded as the temperature has risen.
Aquatic ecosystems According to the IPCC, the impacts that will have the most serious socioeconomic consequences are: population displacement, salt- water intrusion in low areas (with the associated degradation of potable water sources), changes in storm regimes, increased erosion and modification of coastal morphology, displacement of crop areas, disruption of access to fishing areas, negative impacts on biodiversity (including mangroves and wetlands), salinization and overexploita- tion of water resources (including groundwater, which would affect the availability of potable water for coastal populations), and pollu- tion and acidification in coastal and marine environments.
Freshwater systems The IPCC considers freshwater systems to be very sensitive to cli- mate change. There are few studies of how changes in temperature could affect species in rivers and lakes. However, it is expected that falling water levels in rivers and reservoirs alone would negatively affect the species that develop there. Furthermore, studies conducted in other latitudes indicate that rising water temperature would mod- ify the thermal cycles of lakes and the solubility of oxygen and other elements, thereby affecting the structure and functioning of these ecosystems.
The effects of climate change on wetlands are still very uncertain and are seldom included in global models of climate change effects. However, in general terms, temperature increases, rising sea level, changes in precipitation, and higher evapotranspiration, together with changes in land use and overexploitation of water resources, will degrade these goods and services. These changes could affect aquatic birds that depend on wetland habitats and it is possible that they will contribute to desertification.
52 Effects of climate change on Mesoamerica
Mangrove forests and coral reefs Mangrove forests and reefs are highly interconnected habitats. Reefs, like mangrove forests, stabilize and protect coastal landscapes, contribute to the maintenance of coastal water quality and function as the main habitat of numerous mammals, birds, reptiles and fish, many of which are commercially important. The effects of climate change would be added to those produced by the large amount of sediments produced mainly by agricultural activities in the countries of the Mesoamerican reef.
Mangrove forests are possibly the coastal ecosystems that would be most affected by rising sea level, rising temperature, and the higher frequency and increased intensity of hurricanes and storms, with their associated impacts on fishing activity and the food industry based on marine products. In the Mesoamerican reef area, the abundance of some fish species can be up to 25 times higher near mangroves than in areas where these have been destroyed8. Loss of mangrove forests would greatly reduce this diversity. On the other hand, in countries such as Belize, mangrove forests also act as buffer zones against the direct effects of wave action, protecting nearly half the length of the coastline and up to 75% of the coasts of the cays. The degradation of these ecosystems would also increase the vulnerability of coastal infrastructure.
Central America has the second largest barrier reef in the world, extending for 1,000 km from the northeastern Yucatan Peninsula in Mexico to the Bay Islands of Honduras. Rising sea temperature and water acidity has caused the death of large areas of coral, and not just in Mesoamerica. A 1 ºC rise in sea temperature causes episodes of bleaching (often partially reversible) in corals, while a 3 ºC rise can cause their death. Higher water temperature can also increase the incidence of diseases that affect corals and seagrass beds, and influ- ence the quantity and distribution of marine organisms. Moreover,
8 http://central-america.panda.org/about/countries/belize/?uNewsID=16870. Last visit 17-05-09.
53 ABC of Climate Change in Mesoamerica
at an atmospheric CO2 concentration above 450 ppm (currently this is 384 ppm and rising), coral diversity would be lost due to water acidification.
A study based on data for 1977–2001 reveals that the coral cover of the Caribbean reefs diminished by an average 17% in just one year after the passage of a hurricane, without any evidence of recovery for at least eight years after the impact. After hurricanes Emily and Wilma in 2005, significant changes were seen in the physical structure and species diversity of the Cozumel reefs. In addition to the struc- tural and biological damage caused by extreme events, coral reef degradation can have severe impacts on the economies of countries. In Belize, tourism associated with activities in mangroves and reefs contributed 150 to 196 million dollars (12 to 15% of GDP) in 2007. It is also estimated that the presence of these ecosystems prevents losses of 231 to 347 million dollars by helping mitigate the erosive and destructive effects of the sea.
Despite the major impacts of climate change on coastal-marine resources, other factors—such as resource extraction, residential, tourism and commercial development, water pollution by industrial discharges and urban wastes, and agricultural activities—currently exert greater pressure on coastal ecosystem biodiversity.
Coastal zones Significant impacts from climate change and rising sea level are expected for 2050–2080 in all coastal areas of Latin America. With most of the region’s population, economic activities and infrastruc- ture located very near sea level, it is very likely that the coastal zones (beaches, estuaries, coastal lagoons, river deltas) will suffer flooding and erosion, with serious impacts on populations, resources and eco- nomic activities.
The impact on coastal tourism will be considerable in Central America because this sector contributes significantly to GDP
54 Effects of climate change on Mesoamerica
through the creation of jobs, and the promotion of public services and state taxes. Furthermore, this sector would also be affected by storms and rising sea level.
The coasts, coastal cities and ports of Belize, Costa Rica, El Salvador, Mexico and Panama are among the places most vulnerable to climate variability, hydro-meteorological events, and tropical and subtropi- cal cyclones. Between 1909 and 1984, sea level rose 1.3 mm per year in Panama (approximately 9.8 cm in 75 years), thereby increasing its vulnerability to extreme tides. In southern Mexico, the areas of major marine influence would reach up to 50 km inland, in the case of rivers and wetlands.
Fisheries The effects of climate change on freshwater fisheries will depend on the species and local climate modifications. There are information gaps regarding many aspects of marine and aquatic environments. For example, there are no detailed regional inventories documenting the distribution of aquatic and marine species. There is also a lack of information about marine pH, salinity and temperature at various depths.
Despite these limitations, it is considered very likely that climate change will interact with human influences on the oceans to nega- tively affect oceanic fisheries. For example, fishery production is expected to suffer if wetlands and other coastal habitats that serve as nurseries are lost as a consequence of rising sea level and the increased discharge of sediments and agricultural wastes. In Nicaragua, a reduction in the production of shrimp, conch and oys- ters is expected. Even so, IPCC models assume that ocean fisheries will remain stable or grow significantly- if and when management deficiencies are corrected. This last assumption is critical, because fishing has been confronting serious problems of sustainability for many years now.
55 ABC of Climate Change in Mesoamerica
Agriculture and cattle ranching
Generalities of the sector The agricultural sector is considered to be doubly exposed because, on the one hand, it is vulnerable to strong socioeconomic changes associated with the process of economic globalization and, on the other, it is sensitive to climate variations. In addition to purely cli- matic effects, food production and food security are closely related to land degradation and erosion patterns. A paradigm shift will be required for agriculture to confront changes in productive potential and the pressure of increased population.
Climate change impacts agriculture and the rural milieu in many ways. The main direct effects of climate change on agriculture would be changes in the duration and seasonality of crop cycles, physiological alterations from temperatures higher than those to which crops are adapted (which would lead to crop losses), water shortages (which would reduce soil moisture, as well as changes in infiltration and runoff) and increased erosion (due to soil desicca-
tion and greater surface runoff). Increased CO2 concentrations have the potential to raise the productivity of some crops but this effect is limited. Indirectly, climate change would affect the incidence of pests and diseases, the cycling and availability of nutrients in the soil, increased propensity for fires, etc.
All these factors have the potential to reduce agricultural produc- tion, de-capitalize the sector, increase unemployment, encourage migration to urban areas and complicate access to credit, among other problems. Agriculture has traditionally been one of the main sources of employment and a leading generator of revenues for the countries of the region. Although the agriculture sector’s contribu- tion to GDP has declined since 1990, it recently represented nearly 20% of GDP in Belize, Guatemala and Nicaragua, from 10% to 20% in Honduras and El Salvador, and less than 10% in Costa Rica, Mexico and Panama (UNDP, 2003). The agriculture sector is where
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most of the losses due to extreme climate events have been concen- trated. For example, 49% of the losses caused by Hurricane Mitch were concentrated in the agriculture sector, while losses due to droughts could reach 60%. In Mexico, droughts represent 80% of all the agricultural catastrophes that occurred between 1995 and 2003.
In addition, agriculture is linked to maintaining public health through its role as the basic source of foods necessary for nutrition. To sum- marize, the effects of climate change on agriculture would affect human wellbeing and would negatively impact the sector’s potential contribution to national GDP.
Changes in production During El Niño/La Niña events, studies have documented reduc- tions in the growth of mangos and other crops, increases in the incidence of pests and pathogens in corn, potatoes, wheat and beans, and reductions in milk production due to rising temperatures. Crops such as bananas, traditionally cultivated in lowlands, have historically borne the brunt of extreme precipitation and flooding events. Based on climate predictions, it is likely that areas planted with banana will experience even greater impacts. In Mexico, any shift toward warmer and drier conditions could trigger a nutritional and economic disas- ter because agriculture is already under pressure from scant and variable precipitation.
Basic grains have also been subject to fluctuations in production due to climate changes. In South America significant increases have been reported in the production of soybeans (38%), corn (18%), wheat (13%), sunflower (12%) and grasslands (7%). However, in Central America, changes in agricultural productivity are more variable. In Costa Rica it is estimated that a 2 ºC rise would benefit coffee produc- tion, but the same temperature rise, combined with a 15% reduction in precipitation would reduce the country’s potato and rice pro- duction. In Guatemala, with a 1.5 ºC rise in temperature and a 5% reduction in precipitation, bean production would vary from -28% to
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+3%, while for corn it would vary from -11% to +8%, and for rice it would be reduced by 16%. In Mexico, the proportion of the national territory suitable for seasonal corn cultivation would be reduced from 11% to only 4% (Flores et al. 1996), as this particular crop is most vulnerable to climate change. In Honduras, a reduction of 21% in corn production for 2070 is estimated. In Panama, a similar reduction in rice production is estimated for 2100. However, in 2010 and 2050 increases of 9% and reductions of 34% are estimated, respectively. In Nicaragua, a drastic reduction in basic grains is expected, which would affect food security. Nevertheless, there are incipient experi- ences aimed at replacing corn with sorghum in the northern part of the country. The departments of Chinandega, León, Managua and Masaya in Nicaragua will suffer severe reductions in crop yields in the next 50 years. Variations in pest populations and diseases due to cli- mate change will also play a role in reducing agricultural production.
Variations in the production of basic grains could also depend in part
on the response of these crops to higher concentrations of CO2 in the
atmosphere (an effect known as “CO2 fertilization ”). For example,
it is estimated that if the effects of CO2 are not taken into account, grain production would be reduced by up to 30% in 2080. On the
other hand, if the effect of CO2 is taken into account in the fore- casts, grain production would be reduced by 30% in Mexico, but would increase by 5% in Argentina. Production would also increase for other crops such as corn, sorghum and sugarcane. Despite these
increases, experiments on the addition of CO2 have shown that the fertilization effect is short-lived and that eventually other elements critical for plant growth (nutrients, water, organic matter) will limit increased production. For example, a temperature rise of around 2 ºC, combined with lower water availability, would reduce production in tropical countries by up to 60%.
In the case of cattle ranching in Costa Rica, it was found that both prolonged and seasonal dry periods can affect the health of cattle, either due to emerging diseases and pests or the lack of pasture.
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Moreover, higher temperatures lead to lower yields due to the ther- mal stress the animals suffer.
Generally, the interaction of biotic, abiotic and socioeconomic fac- tors (occupational health, disasters, pollution) has an influence on the existence, exposure and susceptibility of an infectious agent that causes a disease in a given host. Demographic and social factors such as urban development and human migration due to droughts, grow- ing poverty in urban areas and environmental degradation could also promote new forms of vector reproduction and disease dispersal.
Overall, higher incidences of vector-transmitted diseases (den- gue and its hemorrhagic variety, malaria, leishmaniasis and yellow fever) are expected. In these diseases, the influence of climate changes is rather indirect, since it is the vectors that respond to the fluctuations in temperature, precipitation, solar radiation and rela- tive humidity. For example, it is known that dengue is commonly transmitted in areas with temperatures above 20 ºC. In Mexico, it has been shown that a 3 or 4 ºC rise in average temperature can double the dengue transmission rate. Furthermore, in coastal areas of that country, the transmission cycles of this disease are corre- lated with sea surface temperature, minimum air temperature and precipitation. Some models predict a substantial increase in the number of people at risk of contracting dengue in Honduras and Nicaragua, as the geographic limits of transmission are displaced, along with rising temperatures.
Malaria would also expand its geographic distribution. This disease presents a serious health risk, particularly in El Salvador, where the risk of transmission is 100%. An increase in the incidence of malaria is also expected in Nicaragua, with seasonal variations from 2010 on. A 1 ºC rise in temperature would increase the occurrence of malaria
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by 1% in Mexico. The risk of contracting this disease would thus be much greater for the entire region in 2030. Increases in malaria -and in the population at risk of contracting this disease- could impact health service costs, including payments for treatments and social security.
Leishmaniasis is a disease associated with prolonged droughts, while leptospirosis is related to floods and problems with stagnant water. Outbreaks of hantavirus have been reported in several Latin America countries, including Panama, after prolonged droughts.
The incidence of non-vector transmitted infectious diseases (chol- era, typhoid fever, salmonellosis, shigellosis, etc.) could also increase, mainly due to changes in the distribution and quality of surface water. Gastrointestinal and respiratory diseases will also be more common. Although gastrointestinal diseases may respond to the incidence of floods or droughts, the absence of basic hygiene infrastructure, over- crowding of the population and water scarcity could be determinant factors in the occurrence of these diseases. In Costa Rica, a rise in the incidence of asthma is expected by 2015, partly due to an increase in temperature and humidity fluctuations. Subsequently, asthma cases could diminish as air quality improves in the Greater Metropolitan Area. The most direct effect of climate change on human health would be sunstroke, which mostly affects the population over 65 years of age and people with pre-existing disease conditions. In Mexico it is estimated that mortality would increase by at least 1% if temperature rose only 1 ºC.
Central America is one of the regions with the highest probability of disasters, due to its geographic position, its high levels of vulner- ability and the increase in natural and human threats. Disasters in the Central American region have increased to an annual rate of 5%
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over the last 30 years. However, climate change alone is not respon- sible for all disasters that occur in the region. Rather, these interact with social and infrastructure factors, such as9 the following: • The concentration in high risk zones of populations with low economic capacity for absorbing the impact of disasters and recovering from their effects; • The establishment of human settlements in areas prone to hazards, such as river banks and wetlands, with fragile and inse- cure living conditions and insufficient social infrastructure and services; • Impoverished rural areas suffer a progressive increase in threat levels due to environmental degradation processes; and • Public and private institutions and national and local govern- ments have weak capacity for risk reduction and management.
There are no detailed studies quantifying the potential future costs associated with climate change in the region. However, based on an analysis of past events, the costs would be significant. It is estimated that between 1970 and 2002 average economic losses caused by disas- ters in the region exceeded 318 million dollars per year. In Mexico, the 1997–1998 El Niño alone was responsible for approximately 204 million dollars in crop losses.
Although the number of deaths due to natural disasters has declined since 1972, the total population affected has increased considerably. The extensive damage associated with Hurricane Mitch (in 1998) was calculated at approximately 8.5 billion dollars, which set back the region’s economic development for a decade or more. Damage due to natural disasters in 2005 reached 6,448 billion dollars in Mesoamerica and the Caribbean. Hurricane Stan produced losses of 998 million dollars in Guatemala alone. This is equivalent to just over 3.4% of GDP for 2004, or 39% of gross capital formation in that country, which had a significant impact on the rate of GDP growth. In comparison, the damage caused by Hurricane Ivan in the Cayman
9 http://www.sica.int/cepredenac/contexto_reg.aspx. Last visit 10/23/2010.
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Islands, Grenada and Jamaica represented 183%, 212% and 8% of GDP, respectively, for those countries in 2004. Meanwhile, Nicaragua is the second country in the world that is most affected by tropical storms. About 25% of its population is at risk from storms and hur- ricanes, and 45% is vulnerable to droughts. In 2007, Hurricane Felix caused losses of more than 300 million dollars in Nicaragua.
Since the effects of these disasters are cumulative and the resilience of systems is reduced following repeated events, the occurrence of more than one natural disaster per year could impact the countries even more severely.
Climate change threatens to paralyze and reverse advances in human development such as the reduction of extreme poverty, the strengthening of public health, improvements in agricultural produc- tion, nutrition and education etc.
One seldom considered factor, but one of great importance for the region, is the stability of the indigenous populations. These communi- ties depend directly on the various resources provided by ecosystems to satisfy many of their basic needs. Due to their geographic, demo- graphic and socioeconomic characteristics, these human groups have low adaptive capacity and high susceptibility to climate changes.
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Annex Coastal zones Gulf of Mexico and the Caribbean Sea susceptible to rising sea level Coastal strand unsuitable for agriculture will be displaced further inland Coastal zones Yucatán affected: and (Los Petenes) Quintana Roo (Sian Ka'an Bay and Chetumal) • • • Forest resources 50% of forest area will undergo changes moist Cold, temperate forests in the mountainous zones of Oaxaca and Chiapas will be the most affected • • Biodiversity Reduced environmental services and ecosystem stability Endemic species show reduction in their ranges • • Sector Mexico human aspects Health and other Increased risk of deaths due to heat waves Increased dengue and malaria • • Agriculture >40% of nation will suffer changes in suitability for corn production Area suitable for seasonal corn will disappear in southern and southeastern regions • • Moderate to strong pressure (10–40%) on southern Mexico by 2030 States more vulnerable to drought in the Oaxaca, south: Quintana Roo, Campeche, and the Chiapas, Yucatan eastern Peninsula Water resources Water • • Climate variables 2–4 ºC rise by 2050 5–20% reduction in precipitation Northern Mexico with greater changes Increase in severe storms and more extreme and prolonged periods of drought 52–58% of country affected by change climate • • • • • Annex 1 sectors of society in Mesoamerican countries of climate change on different Effects
73 ABC of Climate Change in Mesoamerica Coastal zones Sea level rise of 6 to 34 cm by depending 2030, on scenario and assuming a 1.5 ºC temperature rise • Forest resources Modifications to forest cover, diversity, development productivity and Coniferous forest area reduced due to an expansion of the dry zone Coniferous and mixed forests nation)of (3.7% will be affected • • • Biodiversity Sub-tropical zones reduced by giving 32–27%, way to tropical zones (Petén, northern Quiché, Verapaz, Alta southern Izabal, and southeastern areas) Moist and temperate zones reduced by 25% in upper areas of mountain ranges • • Sector Guatemala human aspects Health and other Changes in seasonal of acute Patterns infections, respiratory acute diarrhea and malaria Increase in diarrhea, parasite and skin diseases • • Agriculture Reductions of up to 66% in harvests of some basic grains Crop losses of fruits vegetables, and cereals in watersheds and of sugarcane coffee, and cattle near the coast Responses depend on region and crop: -34 to +15%, Corn: -66 to +3%, Bean: -27 to -16% Rice: • • • In a pessimistic scenario: 10– 50% reduction in runoff and diminished water sources for human and animal Consumption and for irrigation In an optimistic runoff scenario: could increase 15% Water resources Water • • Climate variables Increased temperature Reduction of precipitation year-round and more pronounced dry season Maintenance or expansion of semi-arid areas • • •
74 Annex Coastal zones Effects of rising sea flooding of level: lowlands wetlands, more and coasts, loss coastal erosion, of beaches Severe impacts on coastal infrastructure and structures close to sea level Damage to infrastructure and reduction of water quality in aquaculture areas Flooding of cays Mangroves, wetlands Mangroves, and reefs affected by rising sea level Loss of tourist attractions • • • • • • Forest resources Changes in species, degradation of structure, effects of pests and diseases, increased forest fires Damage to mangroves • • Biodiversity Mortality of corals due to higher ocean temperature and acidity physical storm damage Loss of habitat for commercial fish species Reduction in fishery potential • • • Belize Sector Honduras human aspects Health and other Flooding will affect communication, infrastructure and cities 45% of the population of Belize forced to migrate inland Diminished marine tourism • • • Agriculture Reduction in the production and quality of banana Sugarcane, and corn Floods and higher salinity on crop lands of the coast Greater soil erosion Increased agricultural pests and diseases Corn production reduced by 22% • • • • • of 2 1276 km Higher salinity in aquifers rivers, and ground- affecting water, potable water availability With a 1 m rise all in sea level, the cays will lose their potable water sources lands lost to floods Water resources Water • • • Climate variables 1.8–3.7 ºC temperature rise by 2100 Reduction of 2100 by 37–8% Temperature Temperature increase between 0.8–3 ºC Changes in precipitation from -42 to +18% • • • •
75 ABC of Climate Change in Mesoamerica Coastal zones Loss of 10–28% land area with sea level rise of 0.13–1.1 m Migration of fishery species to deeper waters Reductions of 16–23% in artisanal shrimp fishery volume • • • Forest resources Loss of mangroves • Biodiversity Migration of species to new habitats due to rising sea level Reduction or extinction of marine and continental plant and animal species • • Sector El Salvador human aspects Health and other Increased poverty and worsening nutrition and health, education Reduction in sources of jobs in all sectors Degradation of tourism potential • • • Agriculture Reduction in agri- cultural production (basic grains) Losses due to drought or flooding in the agricultural up to sector, $45million in 2100 Losses of 80% in cattle production Losses of Infrastructure for production • • • • Increased flooding Saltwater intrusion would affect potable water sources Water resources Water • • Climate variables Temperature Temperature increase of 2.5–3.7 ºC in 2100 in Variation precipitation of -37 to +11% in 2100 Intensification of dry season and droughts • • •
76 Annex Coastal zones Forest resources Modifications in forest cover, diversity, growth and productivity • Biodiversity Life zones would change in 72% of country • Sector Nicaragua human aspects Health and other Malaria increased 38–150% • Agriculture Atlantic zone the least affected by water resource reduction Reductions of 34–60% in hydroelectric energy generation in 2100 Reduction in aquifer capacity Runoff diminished 37–57% in 2100 Water resources Water • • • • Climate variables Precipitation 8–37% decline 0.8–3.7 ºC temperature rise • •
77 ABC of Climate Change in Mesoamerica Coastal zones Breaches of the coastline and expansion of areas prone to tidal flooding With a 0.3 m sea 60% of level rise, Puntarenas would be flooded (90% with a 1m rise) • • Forest resources Migration of loss of species, diversity • Biodiversity Reduction of montane, wet premontane, and rainforest life zones tropical and Wet dry tropical life zones would be the most affected Plant and animal species at the lowest or tropical belt would be the most vulnerable • • • Sector Costa Rica human aspects Health and other Agriculture Reductions in production of rice, beans and potatoes Coffee increases production with a temperature 2 ºC. with a good rise, water supply • • Problems of erosion and sedimentation, with repercussions for use of the resource and hydroelectric energy generation Variations (positive and negative, depending on the scenario) in runoff Water resources Water • • Climate variables Reduction of precipitation by 46 to 63% Temperature rise of 3.2–3.5 ºC • •
78 Annex Coastal zones Flooding and displacement of wetlands and coasts Coastline erosion Increased storm flooding • • • Forest resources Changes in floristic composition, migration of species, disappearance of others • Biodiversity Increased land area of drier life zones Loss of ecosystems due to agricultural pressure Migrations and loss of biological diversity • • • Sector Panama human aspects Health and other Increase in human diseases • Agriculture Reduction in rice yields Enhanced corn production to 2010, with subsequent reductions to 2100 • • Increased salinity in coastal aquifers changes Negative in water quality Reduction of up to 26% in river flows Water resources Water • • • Climate variables Increase in precipitation • Source: SEMARNAT (1997), SERNA (1997), MARN-SV (2000), MINAE (2000), MARN-GU (2001), MARENA (2001), BELICE (1997), (2002), MARN-SV (2000), MINAE (2000), MARN-GU (2001), MARENA (1997), SERNA Source: SEMARNAT et al. (2008), Santos y García (2008) . (2007), CATHALAC SEMARNAT-INE
79 ABC of Climate Change in Mesoamerica
Treatment of scientific uncertainty by the IPCC (Adapted from Solomon et al. 2007.)
“Uncertainty” in the scientific context is a measure of the range of variability of a determined measurement or of the probability of occurrence of a determined phenomenon. In other words, scientific uncertainty is a measure of certainty that describes the limits of the knowledge attained. This definition contrasts with the colloquial use of the word, which refers to the lack of clear and certain knowledge of something.
The IPCC distinguishes between confidence levels in scientific knowledge and the probability of the occurrence of certain events.
The confidence level in the precision of a result is described using the following terminology:
Confidence level Precision of the statements
Very high At least 9 out of 10
High About 8 out of 10
Medium About 5 out of 10
Low About 2 out of 10
Very low Less than 1 out of 10
At the same time, the probability of occurrence of an event is expressed in IPCC reports using the following standard terminology:
Probability of occurrence Likelihood of occurrence/outcome
Virtually certain >99%
Very likely >90%
More likely than not >50%
About as likely as not 33 to 66%
Unlikely < 33%
Very unlikely < 10%
Exceptionally unlikely < 1%