Climate Change and the Mediterranean Region
- EXECUTIVE SUMMARY
Water shortages and poor harvests during the droughts of the early 1990s
exposed the acute vulnerability of the Mediterranean region to climatic
extremes. Against this backdrop, the prospect of a major climate change
brought about by human activities is a source of growing concern, raising
serious questions over the sustainability of the region.
This report examines the potential implications of global climate change
for the Mediterranean region. Drawing on the results of recent studies, it
reviews possible changes in climate together with recent trends, the
potential impacts of climate change and the implications for sustainable
One key finding is that future climate change could critically undermine
efforts for sustainable development in the Mediterranean region. In
particular, climate change may add to existing problems of desertification,
water scarcity and food production, while also introducing new threats to
human health, ecosystems and national economies of countries. The most
serious impacts are likely to be felt in North African and eastern
The report concludes that while there is some scope for adaptation,
ensuring the long-term sustainability of the region requires urgent action
to cut global emissions of greenhouse gases.
Specific findings are summarised below.
Hotter and drier times ahead?
If current trends in emissions of greenhouse gases continue, global
temperatures are expected to rise faster over the next century than over
any time during the last 10,000 years. Significant uncertainties surround
predictions of regional climate changes, but it is likely that the
Mediterranean region will also warm significantly.
The outlook for precipitation is much less certain, but most projections
point to more precipitation in winter and less in summer over the region as
a whole. A common feature of many projections is declining annual
precipitation over much of the Mediterranean region south of 40 or 45° N,
with increases to the north of this. Even areas receiving more
precipitation may get drier than today due to increased evaporation and
changes in the seasonal distribution of rainfall and its intensity.
As a consequence, the frequency and severity of droughts could increase
across the region. Changes in large-scale atmospheric circulation - as
represented by the El Niño-Southern Oscillation (ENSO) and the North
Atlantic Oscillation (NAO) - would further effect the occurrence of extreme
An indication of the scale of possible changes is given by one scenario
based on the output from four climate models. This suggests that
temperatures could rise by over 4°C by 2100 over many inland areas and by
over half of this over the Mediterranean Sea. Over the same period, annual
precipitation is projected to decline by 10 to 40% over much of Africa and
southeastern Spain, with smaller - but potentially significant - changes
Aerosol emissions may counter some of the effects of greenhouse gases in
some areas. But, in the long term prospect remains one of hotter, drier
conditions throughout the Mediterranean region as the relative influence of
greenhouse gases increases over time.
Coastal flooding and erosion
As the world warms, global sea levels will rise as oceans expand and
glaciers melt. Around much of the Mediterranean basin, sea levels could
rise by close to 1 m by 2100. As a consequence, some low-lying coastal
areas would be lost through flooding or erosion, while rivers and coastal
aquifers would become more salty. The worst affected areas will be the Nile
Delta, Venice and Thessaloniki where local subsidence means that sea levels
could rise by at least one-and-a-half times as much as elsewhere.
Climate shows possible signs of change
On a global scale, there is increasing evidence that climate is changing
and of a discernible human influence. The high natural variability of the
Mediterranean climate make both the detection of climate change and
attribution of its cause very difficult. Nevertheless, observations suggest
that climate may already be changing in the region.
Land records for the western Mediterranean show slight trends towards
warmer and drier conditions over the last century. In contrast, parts of
the eastern Mediterranean have experienced cooler, wetter conditions in
recent times than earlier this century. Surface water temperature records
for the last 120 years show little overall trend but deep water records for
the western Mediterranean show a continuous warming trend since 1959.
During the period 1952 to 1992, the number and frequency of heat waves
affecting the region has increased. The early 1990s were notable for
recurrent droughts and for periods of intense rainfall in the western
Mediterranean and for extreme cold events and rainfall in the east. Recent
climatic extremes are linked with the exceptional behaviour of ENSO and of
the NAO. Record-breaking NAO values occurred in 1983, 1989 and 1990, while
the prolonged 1990 to 1995 El Niño event was the longest on record.
While all such trends and extremes could have occurred naturally, they are
broadly consistent with the potential effects of greenhouse gas emissions
and aerosol emissions to-date.
Increase in extent and severity of desertification
While much desertification is attributed to poor land use practices, hotter
and drier conditions would extend the area prone to desertification
northwards to encompass areas currently not at risk. In addition, the rate
of desertification would increase due to increases in erosion, salinisation
and fire hazard and reductions in soil quality. As a result, the process of
desertification is likely to become irreversible.
The economic and human costs of an increase in desertification would be
tremendous - even today, the annual costs of desertification in Tunisia and
Spain are US$100 million and US$200 million, respectively.
Increased frequency of water shortages and decline in water quality
It is likely that the first impacts of climate change will be felt in the
Mediterranean water resource system. Reductions in water availability would
hit southern Mediterranean countries the hardest. In Egypt, Libya, Tunisia,
Algeria, Morocco, Syria, Malta and the Lebanon, water availability already
falls below, or approaches
1,000 m3 per person per year - the common benchmark for water scarcity.
Even relatively well-endowed countries, such as Spain, Greece and Italy,
could suffer ever-more frequent regional water shortages due to the twin
problems of climate change and rising demand. Crete, for example, could
experience serious water shortages in five out of six years by 2010.
Some water supplies could become unusable due to the penetration of salt
water into rivers and coastal aquifers as sea level rises. Water pollution
- already a major health hazard in the region - would become still worse as
pollutants become more concentrated with reductions in river flow.
Food security threatened by falls in production and world price rises
Livestock production would suffer due to a deterioration in the quality of
rangeland associated with higher concentrations of atmospheric carbon
dioxide and to changes in areas of rangeland as climate boundaries move
northwards. In the European Mediterranean, the area of unproductive
shrubland is expected to expand, while in North Africa and the Near East,
most of the steppe rangeland could give way to desert by 2050 or earlier.
Yields of grains and other crops could decrease substantially across the
Mediterranean region due to increased frequency of drought. While losses
may be partially offset by beneficial effects from carbon dioxide, crop
production would be further threatened by increases in competition for
water and the prevalence of pests and diseases and land losses through
desertification and sea level rise.
Climate change effects combined with wider socio-economic factors could
cause cereal production over much of southern Europe to become untenable.
At Kardista in central Greece, for example, the chance of obtaining current
yields of maize could drop to close to zero by 2050, while in Spain,
irrigation problems could force maize out of production.
In North Africa and the Near East, changes in average climate associated
with a doubling of carbon dioxide could cause yield losses of over 20% for
wheat, corn and other coarse grains - even before allowance is made for
losses through other causes. In coastal areas, large areas of productive
land may be lost through flooding, saline intrusion and waterlogging. In
Egypt, for example, agricultural production may cease altogether over an
area extending 20 km inland.
World prices for many key commodities such as wheat, maize, soybean meal
and poultry could rise significantly as a result of global climate changes.
Not only might Mediterranean countries loose substantially in economic
terms, but the combination of higher prices and crop losses would lead to a
deterioration in levels of food security in, particularly, southern
New, widespread risks to public health
Reductions in food security would increase the risks of malnutrition and
hunger for millions in the south. The combination of heat and pollution
would lead to an upsurge in respiratory illness among urban populations,
while extreme weather events could increase death and injury rates. Water
shortages and damaged infrastructure would increase the risk of cholera and
dysentery. Higher temperatures would increase the incidence and extent of
infectious diseases, such as malaria, dengue fever, schistosmaisis and
Many valuable ecosystems would be lost
Many valuable ecosystems could be lost as species fail to keep up with the
shift in climate boundaries and/or find their migration paths blocked by
human activities. Wetland sites will face the dual threats of drying out
and sea level rise. Up to 85% of wetland sites in southern Europe could
disappear with a 3 to 4°C rise in temperatures. In Tunisia, for example,
rising temperatures could contribute to the loss of all food plants and
breeding waterfowl and the disappearance of nationally important fisheries.
Economic activity undermined in coastal zones
Industries, infrastructure and heritage sites in the coastal zone would be
threatened by inundation or erosion due to sea level rise. For example, a
rise in sea level of just 0.5 m would flood the western part of Kastala Bay
(Croatia) harbour and cause serious degradation to the historic cities of
Cres (Croatia) and Venice (Italy). Hydroelectric power output could be
constrained by water shortages, with potentially serious knock-on
implications for both domestic and industrial users.
Serious social disruption as the livelihood of millions is threatened and
international tensions over resources mounts.
Serious social disruption could occur as millions are forced from their
homelands as a result of desertification, poor harvests and sea level rise,
while international disputes over shared water resources could turn into
conflict in the face of declines in water availability and increased demand.
Losses to national economies
National economies would be adversely affected not only by the direct
impacts of climate change, but also through the cost of adaptive measures
and the knock-on implications of changes elsewhere. Quantitative estimates
of financial costs are unreliable but in general, developing countries are
expected to suffer larger relative economic damages than developed
Sustainable development hinges on international action to cut greenhouse
Future climate change could critically undermine efforts for sustainable
development in the Mediterranean region through its impacts on the
environment and social and economic well-being. While in many respects
climate change exacerbates existing problems rather than creates new ones,
the sheer magnitude of the potential problem means it cannot be ignored.
There is some scope for adaptation, but the fact that many measures would
be beneficial irrespective of climate change suggests that radical changes
in policies and practices will be needed. It is also vital that developed
countries meet their obligations to assist adaptation in developing
countries through access to know-how and financial assistance.
Ultimately, however, the long-term sustainability of the Mediterranean
region requires keeping climate change within tolerable bounds. Current
understanding of safe limits points to the need for prompt international
agreement - and action - to make the drastic cuts in emissions of
greenhouse gases required to stabilise atmospheric concentrations of these
In 1993, tourists from Malaga to Athens and from St. Tropez to Malta were
confronted by exhortations to "Save it" as the region was hit by its fifth
year of drought after winter rains failed to replenish the reservoirs and
aquifers (Pearce, 1993). Serious as such events were, they pale in
comparison with the potential impacts of a human-induced climate change.
Atmospheric concentrations of greenhouse gases1 are rising as a result of
human activities and, in particular fossil-fuel use, land-use changes and
agriculture. Greenhouse gases occur naturally in the atmosphere, where they
allow solar radiation to reach the Earth unhindered but trap a proportion
of outgoing radiation. In this way, greenhouse gases play a critical role
in maintaining the heat balance of the Earth. But as concentrations rise,
scientists believe the world will warm.
In 1986, the Scientific Committee of Problems of the Environment proclaimed
that global warming "should be considered one of today's most important
long-term problems" (Bolin and others, 1986). Research over the last 10
years has reaffirmed the magnitude of the looming threat. In 1996, the
Intergovernmental Panel on Climate Change (IPCC)2 reported for the first
time that past emissions appear to have had "a discernible influence on
global climate" (IPCC, 1996a). The IPCC further found that, if current
trends in emissions continue, this could cause a rate of warming over the
next century "probably greater than any seen in the last 10,000 years".
The magnitude, and possible immediacy, of a major change in climate has
alarming implications for countries world-wide as both ecological and human
systems are fundamentally dependant on climate. The Mediterranean region3
is particularly vulnerable to climate change as over much of the region,
summer rainfall is virtually zero. Water scarcity is endemic and changes in
the water balance would have substantial implications for, amongst other
things, agriculture and water supplies. This vulnerability is compounded by
the ongoing desertification of much of the region, together with population
growth and poverty in, particularly, the southern Basin.
Over the last five years, a number of studies have assessed how climate
change may affect the Mediterranean region. From these, it is clear that
while many uncertainties remain, climate change will have profound and
far-reaching implications for the 350 million or so people who live in the
Mediterranean region today - and for generations to come. This report draws
on recent work to examine, first, how climate may change and what recent
observations show. It then moves on to describe some of the potential
impacts of future climate change and their significance in light of recent
trends and, finally, discusses the implications for sustainable development
in the region.
Figure 1: The Mediterranean region.
2. FUTURE CLIMATE CHANGE
Climate varies naturally on all timescales from decades to millennia due to
changes in atmospheric and ocean circulation, solar output and volcanic
activity. However, future climate change will be dominated by human
influences unless and until the composition of the atmosphere is
Stabilisation of concentrations of carbon dioxide - a key greenhouse gas -
requires cuts in emissions of between 50 and 70%. Emissions of other gases
would also have to be reduced significantly - or even stopped completely -
if atmospheric concentrations are to be stabilised and the risk of climate
change reduced. This section, examines the potential implications for both
global climate and climate in the Mediterranean region if cuts of this
magnitude are not achieved.
Global Changes in Climate
The magnitude and rate of future climate change will depend on the amount
of greenhouse gases emitted, the sensitivity of climate to these gases, and
the degree to which the effects are modified by aerosol emissions. The IPCC
present six scenarios of future emissions, based on widely differing
assumptions of future population and economic growth, energy consumption,
technological developments and land use. These all show that atmospheric
concentrations of greenhouse gases will continue to rise throughout the
21st century unless there is concerted action to curb emissions (Houghton
and others, 1996).
The climatic impact of this rise in greenhouse gases will be modified by
the influence of aerosol emissions (Box 1). Unlike greenhouse gases, the
effects of aerosols are localised and short-lived. Thus, their overall
effect is likely to be to mask - rather than to offset - the much more
fundamental, long-term influence of greenhouse gases on climate at some
locations. Nevertheless, aerosols could exert a strong influence on the
climate experienced at some locations and the IPCC make a range of
different assumptions over future aerosols in their various emissions
Box 1: The Aerosol Effect
Aerosols are microscopic airborne particles. Natural sources include dust
storms, fires and volcanic eruptions. Human sources include the combustion
of fossil fuels and the deliberate burning of forests and fields. The
climatic impact of aerosols depends on their size and composition. Some
aerosols, such as soot, may have a warming effect. Others, such as sulphate
aerosols, are believed to have a cooling effect. The dominant effect is,
however, currently thought to be one of cooling, although some uncertainty
surrounds even this because of uncertainties over the indirect effects of
In any case, the cooling effect is not, according to the IPCC, "...a simple
offset to the warming effect of greenhouse gases" (Houghton and others,
1996). Aerosols tend to have a much shorter lifetime in the atmosphere than
greenhouse gases. While greenhouse gases may stay in the atmosphere for
centuries, volcanic aerosols tend to stay in the atmosphere for months to
years. The atmospheric lifetime of most aerosols of human origin is still
shorter - only a few days.
The short lifetime of aerosols of human origin means that their effects
will be fairly localised and that, unlike greenhouse gases, aerosols do not
constantly build up in the atmosphere. This has two important implications.
* The relative impact of aerosols is expected to become less as time
* If all emissions from fossil fuel burning were stopped tomorrow,
the cooling from aerosols would end within a week, while greenhouse warming
would continue for decades to centuries.
Sulphate aerosols are also major contributors to acid rain and emissions
subject to controls. If, and when, emissions are reduced, their climate
effect will decrease also. Not controlling acid emissions to try and
mitigate the effects of greenhouse gases is not considered an option due to
their devastating effect on crops, ecosystems and materials.
Under the IPCC's "mid-range" emissions scenario (IS92a), concentrations of
greenhouse gases reach the equivalent of double pre-industrial levels of
carbon dioxide by 20304 - and continue to rise thereafter (Carter and
others, 1994). As a result of this, and allowing for potential increases in
aerosol emissions, the IPCC calculate that global temperatures will climb
by between 1.4 and 2.9°C by the year 2100, with a best-estimate of 2°C
(Kattenberg and others, 1996). This range in values reflects scientific
uncertainty over the sensitivity of the climate system to changes in
greenhouse gas levels. Even values at the low end of this scale suggest a
rate of warming greater that any seen in the past 10,000 years.
Even this may be an under-estimate of changes to come. The IPCC's emissions
scenario assumes that emissions of aerosols increase markedly, creating a
strong cooling effect. This is unrealistic. No account is taken of the
Second Sulphur Protocol or of amendments to US car emissions. Moreover, as
the World Energy Council point out, if emissions were to increase as
projected, then this "would cause deposition levels that exceeded the
'critical loads' for most ecosystems in South and East Asian regions" (WEC,
Given this, emissions of aerosols are likely to be controlled much earlier
than envisaged in the IPCC's main scenario and the global warming will be
consequently greater. Figure 2 compares projected changes in global mean
temperature under the IPCC's mid-range scenario with increasing aerosols
and using the same greenhouse gas scenario but with constant 1990 aerosols.
Assuming constant 1990 aerosols, global temperatures would increase by
between 1.6 and 3.5°C by 2100, with a best-estimate of 2.4°C. If greenhouse
gas emissions conformed to the highest of all the IPCC's scenarios then
temperatures would rise still further - by up to 4.5°C by 2100 (Kattenberg
and others, 1996).
Figure 2: Global mean temperature changes from 1990 to 2100 under the
IPCC's mid-range emission scenario (IS92a) and different climate
sensitivities (Kattenberg and others, 1996). The full line shows
temperature changes assuming aerosol emissions increase, while the dashed
line is for constant 1990 aerosols.
As the world warms, global precipitation is expected to increase on average
and other aspects of climate will change. The process of climate change
will, however, not be a smooth, gradual process. Rather, the IPCC state,
"[as] future climate extends beyond the boundaries of empirical knowledge,
the more likely outcomes will include surprises and unanticipated rapid
changes." (IPCC, 1996a).
Increasing temperatures will cause sea levels to rise as glaciers melt and
the water in the oceans expands. Under the IPCC's mid-range emissions
scenario, global sea levels could rise by 20 to 86 cm by 2100, with a best
estimate of 59 cm (Warrick and others, 1996). If aerosol emissions are held
constant at 1990 levels, then sea levels could rise more - between 23 and
96 cm by 2100, with a best-estimate of 55 cm. A rise of 50 cm is between
two and five times the rise in the past century. Time lags in the onset of
melting mean that sea levels would continue to rise many centuries after
2100, even if concentrations of greenhouse gases were stabilised by then.
Significant uncertainty surrounds the projections of sea level rise. This
is largely because of uncertainty over how much ice will melt. A particular
concern is the fate of the West Antarctic ice sheet - this would cause a
rise in sea level of up to 6 m. This threat is generally considered as
uncertain and remote in time compared with the more immediate threat posed
by the potential rise in sea levels over coming decades. However, the
relatively recent discovery that ice shelves in Antarctica may be melting
from beneath due the presence of warm water from the deep oceans adds to
concern over the stability of the continental ice sheets (Jenkins and
Climate Change in the Mediterranean Region
As the world warms, climate will change in the Mediterranean region.
However, considerable uncertainty exists over just what form these changes
may take. This is primarily because of the acknowledged weaknesses of
global climate models (GCMs) in assessing regional climate changes (Box 2).
While such uncertainties are frustrating, the option of ignoring the
prospect of a major change in climate is no more acceptable. Scientists are
confident that global warming due to current trends in emissions will be
accompanied by significant changes in local climate. Decisions must be
taken on the basis of the best information available, taking account of the
uncertainties, and not on the simply-wrong assumption that future climate
will be the same as in the past.
The following sections draw on the results of variety of studies to give an
impression of how climate may change in the Mediterranean region as we move
into the 21st century. Where possible, the results from several studies are
compared to give a sense of a range of possible outcomes.
Box 2: Climate Models and their Limitations
Most regional studies of future climate change use output from global
circulation models (GCMs) of the atmosphere and ocean. In these models, the
physical laws and empirical relationships that describe atmospheric and
oceanic systems are represented by mathematical equations. The many complex
processes - such as the melting of sea ice and formation of water vapour -
that influence climate are taken into account.
By changing the inputs to GCMs, scientists can assess the effects of
increasing concentrations of greenhouse gases on the climate system. The
majority of experiments to-date are 'equilibrium response' experiments and
assess the ultimate impact of a sudden doubling of concentrations of carbon
dioxide. Recently, attention has focused on more realistic 'transient
response' experiments. These experiments measure real-time climate changes
in response to progressive increases (typically 1% per year) in carbon
All climate models have a number of limitations:
* The coarse resolution of global climate models means they do not
adequately depict many geographic features and the interactions between the
atmosphere and the surface;
* Natural variations in local climate are much greater than those in
climate averaged over continental or larger scales;
* The uneven spatial impact of aerosols - not only have few model
experiments taken aerosols into account, but those that do include only
very simplified effects ; and
* Land-use changes - such as deforestation and desertification - are
currently seldom allowed for, but will substantially affect local climates.
Despite these limitations, scientists are confident in GCM results for
large-scale changes in climate. Confidence in local and regional
predictions is, however, lower as most models do not represent current
climate well on this scale and projections vary widely. But, as climate
scientist Tom Wigley observes, "[in] spite of the problems that plague
current GCMs, they are the best tool we have for projecting future changes
in climate at a regional level." (Wigley, 1992). Nevertheless he cautions,
model results "should be treated strictly as scenarios of possible future
climate and not as predictions."
Changes in Temperature
Rising concentrations of greenhouse gases alone could cause warming over
the Mediterranean region similar in magnitude to the global increase.
Results from four equilibrium experiments indicate that temperatures over
the region as a whole could rise by about 3.5°C between now and the latter
half of the 21st century in response to a doubling of carbon dioxide (or
its equivalent) (Wigley, 1992). According to three transient model runs,
about half of this rise - between 1.4 and 2.6°C - could occur by the 2020s
(Rosenzweig and Tubiello, 1997). There is no evidence of marked seasonal
differences in response.
These results are towards the high end of expectations as the models used
have middle to high sensitivities5. An impression of the full range of
possible outcomes is given by an analysis of output from nine transient
models for southern Europe and Turkey6 (Kattenberg and others, 1996). This
points to temperature increases of 1 to 4.5°C (with a mid-point of about
2.5°C) during the winter and summer by the latter half of the 21st century.
Even if emissions of greenhouse gases were stabilised by then, temperatures
would continue to climb for several decades due to time lags in the
response of the oceans.
There will be marked regional differences in the rate of temperature
increase experienced at different locations - although there is wide
disagreement between the patterns of change projected by the various models
(Wigley, 1992 and Cubasch and others, 1996). A picture of possible changes
is given by an average of the output from four equilibrium experiments,
statistically down-scaled for further local details (Figure 3; Palutikof
and Wigley, 1996)7. The results show that temperatures across the region
could rise between 0.7 and 1.6°C for every degree rise in global mean
Figure 3: Model average temperature changes (°C) over the
Mediterranean region for every °C rise in global mean temperature resulting
from rising concentrations of greenhouse gases (Palutikof and Wigley,
1996). The map values can be seen as broadly indicative of conditions which
may exist around 20308. Areas where temperatures are projected to rise less
than the global mean are shaded.
The greatest rates of temperature increase oc
cur over Africa, the Ukraine and eastern Turkey, while the lowest rates of
change occur over the Mediterranean Sea. The coastal zones are areas of
rapid transition. Between now and 2100, temperatures could have risen by up
to: 2.5 to 3°C over the Mediterranean Sea, 3 to 4°C over coastal areas and
4 to 4.5°C over most inland areas, with increases of up to 5.5°C over
Morocco9. This general pattern of change suggested by these results is
physically reasonable as warming over the sea is likely to lag behind that
over land areas. Also, these findings are broadly similar to those from
more detailed model experiments (Cubasch and others, 1996)10.
These results do not take account of possible increases in aerosol
emissions which could mask some of this warming. One transient experiment
suggests that aerosols may reduce warming over the Mediterranean region by
1-2°C over a period from 1795 to 2030-2050 (Mitchell and others, 1995). The
net effect may even be to give an impression of cooling over the central
Mediterranean in summer over the next few decades (Hasselmann and others,
1995). Given the likely exaggeration of aerosol effects discussed earlier,
such results probably over-estimate the potential for local cooling. But,
in any case, the long-term prospect remains one of warming throughout the
Mediterranean region as the relative influence of greenhouse gases
increases over time.
Changes in Precipitation
The prospects for precipitation over the Mediterranean region in a warmer
world are highly uncertain due to the general weakness of GCMs in
predicting regional precipitation. Models offer conflicting evidence over
how precipitation may change on average over the Mediterranean region. Two
out of three equilibrium experiments presented in one study suggest an
overall increase in precipitation across the region (Rosenzwieg and
Tubiello, 1997). However, recent transient model runs for the 2020s suggest
an overall decrease of between 1.5 and 7.3% (Rosenzwieg and Tubiello,
Most equilibrium and transient experiments show a widening in the seasonal
precipitation gradient with more precipitation in winter and less in
summer. An average of four equilibrium model results for the whole
Mediterranean region suggests an increase in winter precipitation of 10%
and a decrease in summer precipitation of 10% between now and 210011
(Palutikof and others, 1992). This finding is broadly supported by a more
recent comparison of nine transient model runs for southern Europe and
Turkey (Kattenberg and others, 1996). In this case, most models suggest
increases in winter precipitation of up to 10% and reductions in summer
precipitation of 5 to 15% by the latter half of the 21st century.
The patterns of precipitation produced by different model runs are so
divergent that it is difficult to have confidence in any single projection.
Nevertheless, a common feature of many model runs is decreasing annual
precipitation over much of the Mediterranean region south of 40 to 45oN,
and increasing precipitation north of this (see for example, Cubasch and
others 1996, Barrow and Hulme, 1995 and Palutikof and Wigley, 1996). This
is illustrated by a scenario based on the average results from four
equilibrium models, statistically down-scaled to give a sense of more
localised changes12 (Figure 4, Palutikof and Wigley, 1996).
Figure 4: Model average precipitation changes (%) over the
Mediterranean region for every °C rise in global mean temperature resulting
from rising concentrations of greenhouse gases (Palutikof and Wigley,
1996). The map values can be seen as broadly indicative of conditions which
may exist around 203013. Areas where precipitation is projected to decrease
In this scenario, annual precipitation changes across the region range from
-12% to +13% per °C rise in global mean temperature. This translates into
annual precipitation decreases of between 10 and 40% over much of Africa
and southeast Spain, and of up to 10% over central Spain, southern France,
Greece and the Near East by 210014. There is also the suggestion of
possible increase in precipitation of up to 20% over central Italy.
However, as the authors stress, confidence in these scenarios is low
because of the uncertainty associated with GCM results for regional
In the short-term, aerosol effects may counter the effect of rising
concentrations of greenhouse gases in some areas. Results from transient
experiments for around the middle of the 21st century suggest that once
aerosol effects are allowed for precipitation over southern Europe and
Turkey as a whole may increase slightly (Kattenberg and others, 1996).
These changes are far from certain as they depend critically on both the
aerosol scenario used and how aerosols are represented in the models. In
any case, a long-term model run for the Mediterranean region suggests that
from 2050 onwards precipitation would decrease markedly as the relative
influence of greenhouse gases grows (Palutikof and others, 1996b).
Clearly, there remains considerable uncertainty over how precipitation will
change over the Mediterranean region in response to the changing
composition of the atmosphere. However, the balance of evidence seems to
suggest reductions in precipitation over much of the region, with a
possible transitional period for some areas due to aerosol effects.
Changes in Moisture Availability
In terms of the ecological and social impacts of climate change, changes in
moisture availability are more important than changes in precipitation or
temperature alone. Low levels of moisture availability are associated with
Moisture availability is determined both by water gains from precipitation
and water losses through runoff and evapotranspiration15. As temperature
increases, evapotranspiration will also increase (all other things being
equal). This means that even where precipitation is projected to increase,
actual moisture availability could go down if the gains are outweighed by
losses. The projected widening of the seasonal precipitation gradient is
also likely to reduce water availability during the growing season
(Kattenberg and others, 1996; Wigley, 1992). This is because extra
precipitation in winter may not be stored in the soil, but lost as runoff.
The occurrence of precipitation in intense episodes has a similar effect
(Segal and others, 1994).
GCMs are particularly weak at determining moisture availability. This is
partly because potential evapotranspiration is not properly assessed by
GCMs due to crude treatment of the hydrological cycle (Rind and others,
1992) and partly because of the huge uncertainties over future
precipitation. Despite this, there is a high level of consistency in model
results for southern Europe and Turkey, with models showing an overall
reduction in summer moisture availability in response to rising
concentrations of greenhouse gases (Kattenberg and others, 1996). Results
from three equilibrium experiments for southern Europe and Turkey suggest
that soil moisture would decrease over the whole region by 15 to 25% during
the summer (IPCC, 1992). A preliminary assessment of changes in the water
balance over the eastern Mediterranean from Turkey through to Egypt also
found a tendency for a northwards shift of the desert line (Segal and
Evidence of reductions in water availability over much of the Mediterranean
region during both winter and summer comes from a recent transient
experiment (Gordon and O'Farrell, 1996). This is supported by work for the
region using average temperature and precipitation output from four
equilibrium experiments (Palutikof and others, 1994 and 1996b)16. This
study indicates an unfavourable shift in the ratio of precipitation to
evapotranspiration throughout the whole Mediterranean region in every
season17. The greatest effects are over the north of the region, extending
over the Italian mainland, Sardinia and Corsica, in spring and autumn. The
impact on human activities may, however, be most acute in the south of the
region where water is in particularly short supply even now.
Again in the near-term, the effects of increased concentrations of
greenhouse gases may be mitigated in some areas by the effects of aerosols.
Two transient experiments show that if aerosol effects are included, then
soil moisture over southern Europe and Turkey as a whole could increase,
rather than decrease (Kattenberg and others, 1996). However, exaggeration
of aerosol effects and the localised nature of their impacts means that
some areas may still experience drier conditions. Moreover, these findings
are only relevant to around the middle of next century. Beyond this, the
relative influence of greenhouse gases is expected to grow and the
long-term prospect is one of a drying out of the whole Mediterranean region.
Changes in Extreme Events
As climate changes the frequency of extreme events in the Mediterranean
region will change in response to changes both in average climate and in
climate variability. Warmer conditions over the Mediterranean region should
lead to an increase in the occurrence of extremely high temperatures and a
decrease in extremely low temperature events. One study finds that by
around the middle of the next century, current maximum temperatures in
Athens could be exceeded in most months (Barrow and others, 1995).
Similarly, in areas experiencing a general decrease in precipitation,
droughts are likely to become more frequent as the probability of dry days
and the length of dry spells increases. The converse is true for areas
where precipitation increases. One study reports that the probability of a
dry spell lasting more than 30 days in summer in southern Europe would
increase by a factor of between two and five on a doubling of carbon
dioxide (Gregory, 1996). A study for Naxos (Greece) further suggests that a
10% reduction in winter precipitation could increase the length of dry
spells by up to 21 to 45%, while a 10% increase in summer precipitation
could increase the length of wet spells by 15% (Palutikof and others,
In general, scientists expect more heavy rain events in a warmer world due
to an intensification of the hydrological cycle. Most models suggest a
general increase in the intensity of precipitation of between 10 and 30% at
most latitudes for a doubling of carbon dioxide (Kattenberg and others,
1996). Storminess may also increase, although this is less certain.
On a wider scale , changes in climate variability will be influenced by
changes in general atmospheric circulation. A major source of year-to-year
variability world-wide is the El Niño-Southern Oscillation (ENSO)
phenomenon)19. ENSO is renowned for bringing climatic disruption world-wide
(Glantz and others, 1991). In the Mediterranean region, El Niño events have
been linked with low rainfall over much of the western and central basins
(Arkin and Xie, 1997, Lamb and Peppler, 1991 Rodó and others, 1997; Rodó
and Comins, 1996).
As yet, scientists are uncertain how ENSO will change in a warmer world -
models do not simulate the phenomena very well and under-estimate the
variability. Nevertheless, a number of models indicate that ENSO events
will continue to occur in a warmer world and there is some evidence that
precipitation anomalies will increase in tropical areas (Kattenberg and
others, 1996). However, a number of papers reviewed by the IPCC suggest
that "much of the effects of global warming may be modulated through a
change in the magnitude and regularity of the warm and cold phases of ENSO"
(Dickinson and others, 1996).
Of still greater significance to the Mediterranean region is the fate of
the North Atlantic Oscillation (NAO))20 although as yet little indication
has been given of likely changes in a warmer world. The state of the NAO
critically affects storm tracks, temperatures and precipitation across
Europe and eastern North America. High values have been linked with low
winter rainfall throughout much of the Mediterranean and cold conditions in
the east (Hurrell, 1995; Palutikof and others, 1996b; Trenberth and Shea,
Despite these uncertainties over exactly how climate variability and
extremes will change in the Mediterranean region, the overall picture does
suggest an increase in the frequency of extreme events and, in particular,
of droughts in the western Mediterranean.
Sea Level Rise
Locally, the apparent rise in sea level will critically depend on local
land movements. Most of the Mediterranean region currently appears to be
stable and is likely to experience a sea level rise comparable with the
global mean - up to about 96 cm by 210021 (Milliman, 1992; Warrick and
others, 1996). The Near East and Alexandria may, however, experience
slightly lower rates of sea level rise - up to 90 cm by 2100 - as the land
appears to be rising slightly.
The worst affected regions seem likely to be the larger river deltas of the
Nile, Thessaloniki and Venice, which are currently subsiding. In these
areas, sea levels could rise by up to 150 cm, 140 cm and 175 cm,
respectively by 2100. Rising sea levels would, in all areas, bring the risk
of inundation, higher rates of erosion and increased saline intrusion into
rivers and aquifers.
3. OBSERVED CLIMATE CHANGES: SIGNS OF CHANGE
Past emissions of greenhouse gases have already affected the Earth's energy
balance and the effects on global and regional climates will become more
marked over time (Santer and others, 1996). This raises two key questions:
is climate changing? And, if so, can the observed changes be attributed to
the changing composition of the atmosphere?
Globally, at least, scientists appear to have detected the first signs of
climate change. Since 1860, mean global temperatures have risen by between
0.3°C and 0.6°C. Warming since the mid-1970s has been particularly rapid
with all eight of the warmest years on record occurring since 1983 (WMO,
1997; CRU, 1997). Early signs are that 1997 may also prove to be a
record-breaking year (Tiempo, 24 Jun 1997).
In 1996, the IPCC announced that the observed warming "is unlikely to be
entirely natural in origin" (IPCC, 1996a). On the basis of further detailed
assessments of patterns of atmospheric and oceanic temperatures and changes
in the hydrological cycle, the IPCC further concluded that the "balance of
evidence suggests a discernible human influence on global climate" .
As global climate appears to be changing, we would expect the Mediterranean
climate also to have changed. Detection of climate change on this scale is,
however, extremely difficult as the high variability in local climates
masks trends in the 'noise' of natural fluctuations. Moreover, the short
period of observations makes the identification of clear trends difficult
and creates uncertainty over the scale of natural variability.
Proving that any observed changes are the result of the changing
composition of the atmosphere is still more difficult due to the weakness
of models in predicting the regional effects of climate change. The picture
is further complicated by the influence of other human activities on
climate (Box 3) which may not only mask underlying trends but could either
accentuate or mitigate the effects of global warming.
For all this, observational records do suggest marked changes in the
climate of the Mediterranean region over recent years. While it is
impossible to be certain if these trends are "real" or if they can be
attributed to atmospheric pollution, a number of aspects of the observed
changes are consistent with a human influence. In either case, absolute
proof will only be available with hindsight - by which time significant
impacts will already be occurring.
Box 3: Human Influences on Regional Climates
Human activities can substantially affect regional climates. The cooling
effects of sulphate aerosols are discussed earlier, but other significant
impacts arise from urbanisation and other land use changes. These effects
complicate the detection of more fundamental climate changes.
* Urbanisation and the associated pollution have the effect of
increasing both temperature and precipitation (Cotton and Pielke, 1995).
Warmer conditions result from a number of processes, including: the slowing
of winds by high buildings, heat released as energy is used and a reduction
in evaporation as rain runs off into drains rather than being retained in
soils. Precipitation increases as air rises and cools over what is
effectively a man-made hill.
The combined effects of urbanisation on local climates can be significant.
In Athens, urbanisation is held responsible for a 1°C rise in maximum
temperatures over the last 20 years which occurred despite a fall in
minimum temperatures (Metaxas and others, 1991). Similarly, rainfall over
the last 70 years has been higher than expected given trends in other
nearby regions (Amanatidis and others, 1993). Over the period 1970 to 1989,
the number of automobiles increased from about 200,000 to over a million,
but also many more, and higher, buildings were constructed between the
Athens National Observatory and the coast.
* Desertification acts to increase maximum daily temperatures and
reduce precipitation. (Cotton and Pielke, 1995). While desertification is
in part a product of climate change, there are also important feedbacks on
local climate. Land degradation tends to reduce soil moisture and this in
turn reduces evaporation resulting in increased maximum temperatures and
lower rainfall. Reductions in vegetation have a similar effect as this
reduces the amount of water captured and then recycled through
evapotranspiration to create rain. Both processes also increases the
reflectively - or "albedo" - of the ground causing higher temperatures in
the day and reducing them at night.
Analysis of temperature data for this century shows that warming
was nearly 0.2°C greater over dryland areas than over land areas as a whole
(Jones, 1994). It is unclear, however, how much of this difference is due
to recent desertification and how much is due to the existing arid state of
many dryland areas. Desertification is a major, long-term problem in the
Mediterranean region and it is possible that this accounts for, at least in
part, the observed decrease in rainfall in some areas.
* Deforestation can increase maximum daily temperatures and reduce
precipitation in much the same way as desertification (Cotton and Pielke,
1995). Experiments in both the Amazon and in southern Nigeria reveal a much
greater range in temperature over cleared ground (Ghuman and Lal, 1986;
Salati and others, 1978). The role of forests in enhancing rainfall is also
well-established - an estimated 50% of rainfall in the Amazon is from local
evaporation and transpiration (Salati and others, 1978). In the
Mediterranean region, deforestation has occurred over many centuries and
the effects are unlikely to distort the recent record - although, of
course, the effects of past deforestation will be ever-present.
* Irrigation and Man-made Lakes have the opposite effect on climate
than desertification as rainfall increases due an increase in local water
availability and day-time temperatures are lowered with an increase in
albedo (Cotton and Pielke, 1995). Few definitive studies of the scale of
these effects have been done but estimates of the possible effects of a
proposal to flood depressions in the Chott region in Algeria and Tunisia
suggest that, as a consequence, local precipitation could increase by up to
150 mm every year (Enger and Tjernström, 1991). The impact of existing
irrigation in, say, Egypt and Israel is unknown, but may have offset some
of the general decrease in precipitation observed locally.
While the effects of such activities on regional climates can clearly be
large, the effects on global climate are very small. Globally, urbanisation
accounts for only an estimated 0.05°C of the observed warming over land
areas this century (Jones and others, 1990). The global impact of
desertification is thought to be still smaller - only a few hundredths of a
degree (Nicholls and others, 1996).
Trends in Temperature
Sea surface temperature records for the Mediterranean region show clear
fluctuations in climate over the last 120 or so years, but little overall
trend (Figure 5). This record shows that temperatures were at a minimum
around 1910 and then rose sharply to a maximum around 1940 after which they
stabilised for around 20 years. After this, while global temperatures
continued to rise to unprecedented levels, the Mediterranean region
experienced a decade of rapid cooling. Warming resumed in the late 1970s,
but still temperatures remained below those experienced in the 1930s and
1940s up until 1989 at least.
Figure 5. Variations in annual sea surface temperatures across the
Mediterranean between 1873 and 1989, as represented by frequency
differences of warm minus cold months. The jagged line shows annual values
while the smooth line highlights variations over decadal and longer
timescales. (Source: Metaxas and others, 1991).
This basic pattern is also evident in sea surface temperature records for
both the eastern and western basins and in the seasonal records, but with
one potentially important difference. The cooling in the east of the region
during the 1970s was much more marked than in the west (Metaxas and others,
1991). As a result, temperatures remained substantially below average in
the east until at least the end of the 1980s. It is also notable that deep
water records for the western Mediterranean show a continuous warming trend
from 1959 (Bethoux and others, 1997).
Land records for the western and central Mediterranean do, however, suggest
a long-term warming trend. While all show a similar pattern of warming and
cooling, the 1970s minimum is much less pronounced at many locations, for
example, Cairo, Marseille, Perpignan and Athens (Metaxas and others, 1991;
Repapis and Philandras, 1988). While this may in part be attributable to
increasing urbanisation over the last 30 to 40 years, the overall impact is
an appearance of warming comparable with that seen in the global record.
This contrasts with Jerusalem (Israel) where annual temperatures in the
mid-1970s were lower than during any other time during the previous 100
years (Repapis and Philandras, 1988).
This east-west difference in temperature trends also shows up clearly when
average conditions for the period 1975 to 1994 are compared with average
conditions during the previous twenty years (Nicholls and others, 1996).
This shows that temperatures were, on average, higher during the recent
period over south-west Europe and north-west Africa. In contrast, average
temperatures in the eastern Mediterranean were lower than during the
previous 20 years. The area of colder conditions is centred on Turkey and
extends west as far as Italy in the north and Libya in the south.
Recent changes in temperature across the Mediterranean clearly fall within
the range of natural variability. But, the general pattern of change is
also broadly consistent with a GCM simulation of temperature changes over
the region associated with the combined effects of present-day carbon
dioxide levels and sulphur emissions (IPCC, 1996a). This being the case,
then it is possible that the warming over the last decade experienced over
much of the region may be a sign of things to come. Only time will tell.
Trends in Precipitation
Since 1900, precipitation decreased by over 5% over much of the land
bordering the Mediterranean Sea, with the exception of the stretch from
Tunisia through to Libya where it increased slightly (Nicholls and others,
1996a). Within these overall trends, regular alternations between wetter
and drier periods are discernible. Records for both the western
Mediterranean and the Balkans indicate major moist periods sometime during
the periods1900 to 1920, 1930 to 1956, and 1968 to 1980 with intervening
dry periods (Maheras, 1987; Maheras and Kolyva-Machera, 1990). Records for
the period 1951 onwards show a slight tendency towards decreasing rainfall
in almost all regions and in all seasons (Figure 6; Palutikof and others,
1996b). The only clear positive trend is in the eastern Mediterranean in
Figure 6: Yearly rainfall anomaly index for the northern
Mediterranean from Portugal to Syria, and including the islands north of
35°N (Palutikof and others, 1996b). The index is for the hydrological
(rainfall) year from September in one year to August in the following year.
Such regional trends underplay the scale of changes in precipitation
experienced locally. Over the period 1975 to 1994, precipitation was on
average more than 17% lower than during the preceding 20 years over much of
north-western Africa, Spain, Italy and Greece (Nicholls and others, 1996).
The recent dryness in the western Mediterranean contrasts with the
conditions elsewhere in northern Africa and the eastern basin. Here,
precipitation was generally higher over the last couple of decades compared
with the previous 20 years. (Nicholls and others, 1996).
Events took an abrupt about-turn in 1996, with drying areas suddenly
experiencing extreme wet conditions and vice versa (WMO, 1997). It is not
clear if this is just a temporary "blip" in overall trends, the start of a
new trend or a return to more "normal" conditions experienced earlier this
century. If the models are broadly correct about precipitation changes in
response to increases in greenhouse gases, the droughts over the western
Mediterranean could be symptomatic of a growing human influence on climate
in the region. Wetter conditions in the east might reflect the stronger
influence of aerosols in this area.
Occurrence of Extreme Events
During the period 1952 to 1992, the number and frequency of heat waves
affecting the Mediterranean region has increased (Geeson and Thornes,
1996), while the early 1990s were notable for a number of extreme events
(Box 4). It is impossible to gauge if the frequency and magnitude of
extremes has increased without a thorough analysis. Nevertheless, records
of ENSO and NAO - both of which are linked with the occurrence of extreme
events in the Mediterranean region - do show exceptional behaviour. This
may, in turn, suggest that the recent history of extremes in the
Mediterranean is unusual.
Box 4: Recent Climatic Extremes in the Mediterranean Region
* The early 1990s were characterised by extreme drought over much of
this region. In 1995, precipitation was less than 75% of normal (1961-1990)
over much of the western Mediterranean (CRU, 1997). Over 1994 and 1995,
Spain received less than 50% of normal at some locations (CRU, 1997).
* In the winters of 1991/2 and 1992/3, rarely seen snowfall fell in
many areas of north Africa and the eastern Mediterranean, while average
temperatures from December to March 1991/2 were the coldest on record in
Turkey (from 1930) and at Jerusalem (from 1865) (WMO/UNEP, 1994).
* Between late September and early November 1993 large sections of
south-eastern France, western Spain, central Portugal, Corsica and northern
Morocco recorded 2 to 3 times the usual precipitation (WMO/UNEP, 1994). In
this period, Madrid had the highest amount of precipitation since records
began in 1854 while in mid-November 1993, Greece and Israel experienced
major floods (WMO/UNEP, 1994).
* In 1995, some interior parts of Egypt saw rainfall for the first
time in nearly half a century. Similarly, conditions in Tunisia and Libya
were exceptionally wet (CRU, 1997).
Both the unusual coldness of over the eastern Med-iterranean over the last
decade and the dry conditions afflicting most of the region have been
linked with exceptionally high values in the NAO (Hurrell, 1995, Palutikof,
1996; Trenberth and Shea, 1997). From the 1940s to the early 1970s, NAO
values decreased markedly. This trend re-versed sharply 25 years ago,
resulting in largely un-precedented positive values of NAO values from 1980
onwards (with the notable exception of the 1995-6 winter). NAO values for
1983, 1989 and 1990 winters are the highest since records began in 1894.
Changes in parts of the western and central Med-iterranean have been
connected to the ENSO the phenomenon. The behaviour of ENSO has changed
mark-edly since 1976/1977, with the record being dominated by El Niño
events and showing only rare instances of La Niña events (Trenberth and
Shea, 1997). The prolonged 1990 to 1995 El Niño event is the longest on
record and would be expected to occur less than once every 2000 years
(Trenberth and Hoar, 1996). La Niña conditions returned abruptly in 1996
but, at the time writing, early signs of an imminent El Niño event have
been observed (Tiempo, 24 June 1997).
The extent to which observed changes in NAO and ENSO are due to increases
in greenhouse gases is not clear. Evidence exists that persistent ENSO
events, at least, may have occurred prior to the period of instrumental
data (Allan and D'Arrigo, 1996). But, as climate scientists Kevin Trenberth
and Dennis Shea point out: "the observational evidence is suggestive that
climate change, for whatever reason, is contributing to [these] changes in
circulation, which in turn alter the distribution of storm tracks and
rainfall." (Trenberth and Shea, 1997).
4. IMPACTS OF CLIMATE CHANGE
Climate change will have diverse and far reaching consequences for the
Mediterranean region (Figure 7). An immediate concern is the potential to
exacerbate existing problems of desertification, water resources and food
production. But ultimately, the impacts will be much wider as the effects
cascade through the social and economic system. While all areas will be
affected, the type and extent of impacts experienced will vary markedly
depending on local circumstances.
Figure 7: Impact of climate change on environment and society
(Milliman and others, 1992).
While there has been an upsurge in impacts studies in recent years, it
remains difficult to be precise over the scale of impacts likely to occur.
This is partly due to fundamental uncertainties in modelling regional
climate change. Most studies focus on the possible impacts of hotter, drier
conditions. However, while current evidence suggests this is the most
likely response to increasing concentrations of greenhouse gases, it must
be noted that confidence in particularly the precipitation scenarios is low
(see Section 2). Also, other activities - and in particular aerosol
emissions - could have an important influence on climate in some areas, at
least in the short term.
Assessment of the impacts of climate change is further complicated by the
need to consider not only the nature of the climate change, but also the
sensitivity of ecological and social systems to change, the degree to which
adaptation is possible and the vulnerability of any given system (Box 5).
The extent to which existing studies take these factors into account
varies. But, common weaknesses include failures to consider: how systems
may evolve under progressive long-term climate change; the interactions
between different sectors; and/or the implications of multiple stress
factors. As a result, it seems likely that the potential impacts of climate
change are understated in many studies.
Nevertheless, there is clear evidence of potentially serious impacts
throughout the Mediterranean region, with the most acute impacts being felt
south of the socio-economic divide in Africa and the Near East. The
following sections, like most of the studies they draw on, focus on the
potential implications on hotter, drier conditions over much of the
Box 5: Assessing the Impacts of Climate Change
The impacts in any particular area will depend on four key factors.
* The magnitude and rate of climate change. This will critically
affect both the extent to which ecological and social systems can withstand
stress and their ability to adapt. The impacts of climate change will be
mediated through not only the direct effects of changes in temperature and
other climate variables, but also the associated rises in atmospheric
concentrations of carbon dioxide and in sea level. The rapid rate of change
anticipated under all but the lowest scenarios of climate change poses a
* The sensitivity of ecological and social systems to climate change.
Low-lying coastal areas are obviously sensitive to changes in sea level,
while the droughts and floods of the 1990s clearly exposed the sensitivity
of, in particular, water supply and food production systems to climate
variations. Other key concerns such as desertification and the degradation
of natural ecosystems probably more immediately impacted by demographic
change and land use practices than by climate - although, even in these
areas, the fundamental change in underlying conditions suggested by climate
change has significant long-term implications.
* The scope for adaptation. Both the rate of climate change and the
uncertainty over the nature of the expected changes makes adaptation
difficult, particularly in the many areas, such as infrastructure
development, where planning timescales are long in relation to the
timescales of the predicted changes.
* The vulnerability of areas. This is determined both by the system's
sensitivity to change and by its ability to adapt. It is likely that
vulnerability will be dictated by as much by economic circumstances and
institutional infrastructure as by inherent sensitivity to climate change.
Finally, it is vital to assess potential impacts of climate change in the
context of other environmental and socio-economic trends. Many countries of
theMediterranean region are already under pressure due desertification,
population growth, tourism, pollution and (legitimate) aspirations to
improve economic well-being. Climate change is just one further stress.
But, the dependence of most human activities on the environment means that
changes can either enhance or undermine development in the region.
In the Mediterranean region, future climate change is likely to aggravate
significantly the existing problem of desertification and critically
undermine the effectiveness of efforts to combat the problem.
The threat posed by desertification to human welfare is internationally
recognised and was the stimulus behind agreement on an International
Convention to Combat Desertification in 1992. UNEP define desertification
as "land degradation in arid, semi-arid and dry sub-humid areas resulting
from various factors, including climatic variations and human activities"
(ICCD, 1994). In the process of desertification, biologically and
economically productive land becomes less productive and less able to
support the communities that depend on it.
Desertification is considered one of the most serious problems facing the
Mediterranean region today (Table 1). The area affected extends across
northern Africa into the Near East and across large parts of Europe,
including Greece, southern Italy, Sicily, Corsica, and the Iberian
Peninsula (UNEP, 1992; Imeson and Emmer, 1992). Every year, Turkey, Tunisia
and Morocco lose around 54237, 18000 and 2200 hectares of land through
erosion, respectively (UNEP, 1987).
Table 1: Extent of desertification (%) in the early 1980s (Mabutt,
The economic and human costs of desertification are enormous. Tunisia alone
spends US$100 million on efforts to combat desertification (Kharrat, 1997).
Desertification in Spain causes an estimated 30,000 million pesetas (US$200
million) economic damages every year (La Mundo, 13 October 1993; La
Vanguardia, 7 January, 1994). Human costs often include malnutrition, the
risk of famine and dislocation of people who are forced abandon their lands.
Much desertification is attributed to human activities going back over
millennia. Human impacts arise from overstocking, over-cultivation and
deforestation and, to a lesser degree, irrigation and urbanisation. Past
degradation is held responsible for decline ancient civilisations within
the region and elsewhere (Box 6). However, drylands are inherently
vulnerable to water stress and drought and as the United Nations Framework
Convention on Climate Change (UNFCCC) points o<br/><br/>(Message over 64 KB, truncated)