Food & Climate
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Unit 3:
Drought in the Mediterranean
The social and economic impacts of drought in the Mediterranean are increasing.
The impact of drought is likely to get worse with time. The population is growing
and cities are getting larger. More food is needed and, as a result, more land
needs irrigating for agriculture. There are inadequate controls on water use and
a lack of political will to change how people use the water resources they already
have.
This satellite picture shows
the Normalised Difference Vegetation
Index for the Mediterranean region. This
index is used to distinguish areas with
different densities of vegetation. The
image shows that areas in Northern
Europe have more dense vegetation than
those close to the Mediterranean Sea.
The difference is caused simply
by climate and water availability.
1. Normalized Difference Vegetation Index
G. Begni, MEDIAS-France
Successful water management aims to prevent water shortages in times of
drought so that agricultural production does not suffer. Many of the risks
involved with water management are caused by the unpredictability of our future
weather. The greatest risk is that of drought.
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Part 1: Importance of drought
Why is drought an important issue in Mediterranean countries?
Mediterranean climates, with hot dry summers and wet winters, are
amongst the most variable in the world. Recurrent drought problems
often affect entire countries for several years in a row and can result in
serious social problems.
In general, rainfall is concentrated between October and March (southern
countries like Algeria or Morocco) or April (northern countries like Portugal or
Italy). Average temperatures in these areas decrease with increasing altitude and
latitude. The weather is characterised by large inter-annual variability. Summer
rainfall (June, July and August) is well below 100 mm in all regions, except in the
north of Spain and Portugal.
In each season, water supply must be
matched with water demands. During
drought periods, the lack of available
water leads to conflicts among water
users and disputes between countries.
These figures show the distribution of rainfall,
temperature and solar radiation for two different
regions in Spain.
Lerida is a region in the northeast of the country
and is characterised by large temperature
differences between summer and winter. Rainfall
is fairly evenly distributed throughout the year
with slightly higher amounts in spring and autumn
than in the summer and winter.
The region of Almeria is around 500 km south of
Lerida. Temperature differences are less extreme
throughout the year but rainfall is very low,
particularly in the summer when it is close to
zero.
1. Climate diagrams for Lérida and Almería.
From: CEDEX.
Agriculture
Over 50% of the land area in the Mediterranean region is used for agriculture
and agriculture is the main user of water. Agriculture consumes over 80% of
the total water demand in Mediterranean African countries and around 60% of
the total water demand in northern Mediterranean European countries. As a
result, drought has a huge impact on agricultural activities.
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Drought affects food production and
food security. Mediterranean cultures
have been farming for several
millennia and farmers are well aware
of the negative impacts of drought.
Irrigated agriculture in the region has
greatly expanded to ensure food
production targets and these targets
have increased the problems
experienced during drought periods.
Connections between current and
predicted future water availability in
the region and food production are
receiving increasing attention.
These figures show the different distribution
of water use for two European countries, one
in the North of Europe and the other one in the
Mediterranean basin. Countries like Spain use
most of their water for agricultural purposes
while industry uses most of the water in
Norway. Note that the total amount of water
used in Spain is around 18 times more than
that used in Norway.
2. Water use in the different sectors in Spain and
Norway. Adapted from AQUASTAT, FAO.
This figure clearly shows
that Spain has access to just
a quarter of the total water
available in Norway. It also
clearly shows that Spain requires
much larger amounts of water
than Norway. As water
availability decreases further, this
imbalance between supply and
demand will get worse.
3. Water use in Norway and Spain
Adapted from AQUASTAT, FAO
Social and policy issues
In the Mediterranean, climate is an essential component of the natural capital
and an important element of sustainable development. Water is not only a major
socio-economic element but an essential cultural element as well. As a result, the
policy debates related to water have been, and will continue to be, vigorous.
Effective measures to cope with water scarcity are known, but are difficult to
implement due to the variety of stakeholders and inadequate means to negotiate
new policies. Any efforts made to improve communication among the scientific
and decision-making communities will have great benefits for the future of water
management in the region.
The social impacts of water scarcity in the Mediterranean are increasing and will
likely be worsen. Cultural impediments to limiting water use are an additional
source of concern.
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Part 2: Drought driving factors
Drought driving factors in the world and the Mediterranean
There are three main factors that we know affect the appearance and
severity of droughts in different regions of the world.
These factors are explained in more detail in other units and here we show how
they are interlinked and how they influence the world in general and the
Mediterranean in particular. These factors are:
· El Niño episodes (ENSO)
· The North Atlantic Oscillation (NAO)
· Other possible influences. The Mediterranean Oscillation
El Niño Southern Oscillation
(ENSO)
The Southern Ocean Oscillation is
made up of two phases, El Niño
and La Niña, and has affected
climate for many
centuries, primarily in the Southern
Hemisphere. Recent research
shows that it may also have some
impact on the climate of the
Northern Hemisphere.
Different temperature and
rainfall conditions are seen during El
Niño and La Niña events, not only in
the Tropical Pacific but also in
distant regions of the world
including the Northern latitudes.
These variations can sometimes
bring about extraordinary episodes
of dangerous floods and droughts.
During El Niño events,
temperatures in the East Pacific
increase along with evaporation
rates and rainfall amounts, while
lower than average rainfall amounts
are seen on the West side of the
Ocean. The opposite conditions are
seen during the La Niña phase.
1. Sea surface temperature anomalies during El niño
and La Niña episodes. Source: NOAA NCEP EMC
CMB GLOBAL monthly Sea Surface Temperature
Anomaly Dec 1997 and Dec 1999) (degree Celsius).
These two maps show the differences in surface
ocean temperatures during El Niño episodes (top
picture) and La Niña episodes (bottom picture).
In order to know if El Niño, La Niña or a Neutral stage are occurring and what
their magnitude is, different indices are used. One measures the differences in
sea surface temperatures across the Tropical Pacific
Ocean (SST), another measures the differences in pressure between the east
and west coasts of the Southern continents (SOI). These indices are used to
make climate forecasts to enable us to predict the possible impacts of extreme
events on our Environment and Society.
This complex system is explained fully in the Weather Unit, take a look if you're
interested!
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North Atlantic Oscillation (NAO)
Just like the Southern Oscillation, there is also a
similar weather cycle in the Northern
Hemisphere. The North Atlantic Oscillation is
one of the main natural factors which influences
climate in the North Atlantic and Mediterranean
regions, particularly in the winter. You can find
out more about the NAO in both the Oceans Unit
and in the Weather Unit.
2. The Positive North Atlantic
Oscillation Index.
http://www.ldeo.columbia.edu/NAO/
The NAO index varies from year to year, but over the past few decades
has remained in one phase for intervals lasting several years. In the picture you
can see a representation of what a positive NAO Index means.
A high-pressure cell is established over the North Atlantic Ocean creating long
periods of very stable and quite dry conditions during the winter for the
Mediterranean basin. During negative NAO conditions, Mediterranean winters are
much wetter.
Other influences over the Mediterranean basin.
Scientists have shown that the NAO is the main factor which influences winter
rainfall patterns and temperature over the Mediterranean region. But not all the
variations we see in the Mediterranean climate can be explained by NAO and
ENSO. Other global climate phenomena may also be responsible.
It's also possible that the extent of the
monsoon in Asia and the amount of rainfall in
the African Sahel region may also influence
the Mediterranean climate.
Differences in atmospheric pressure between
the Eastern and Western Mediterranean
basins sets up the Mediterranean Oscillation.
In a similar way to the NAO, this may affect
wind and rainfall patterns in the region.
3. Atmospheric pressure differences
between Eastern and Western
Mediterranean Basins may influence the
climate of the region.
Part 3: Drought Management
Use of climate information for drought management and early warning
systems
The response to drought is rapid in most areas of the world. So far,
however, these responses have focused on emergency measures
designed to minimise the impact of drought once it has occurred rather
than anticipating and solving the problems before they actually happen.
In general, these emergency efforts have not been used subsequently to provide
the knowledge needed to deal with similar situations in the future. Information
from climate forecasts and/or development of plausible scenarios have not yet
been incorporated into any specific drought action plans.
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Use of climate information
Water management in the Mediterranean is primarily aimed at minimising the
risks of water shortage on agricultural production. Most of the risks are
associated with the unpredictability of future weather patterns. The impacts vary
between users and regions in the Mediterranean.
There has been remarkable progress in the field of climate science and climate
prediction over the last few decades. We now need to include this information
into development planning and implementation processes. This requires an
understanding of how climate variability affects Societies in different countries,
regions and communities.
To enable more effective drought adaptation
measures to be developed, we need better
communication between scientists and
stakeholders regarding climate, water use, food
production and social responses and
interactions in the region.
This map shows the prediction of a drought in
Morocco and other parts of Africa made by the
Climate Prediction Center at NOAA. The
prediction was made six months in advance and
was correct. This shows how climate
information can be used to prepare for, and
minimise the negative impacts of extreme
weather events.
1. Drought prediction in Africa.
Source: NOAA.
Drought early warning systems
Countries are generally unprepared to cope effectively with drought. Local and
National policymakers typically react to a drought event through “crisis
management” rather than through the formulation and implementation of
anticipatory measures commonly referred to as “risk management”. A typical
reason mentioned by decision makers for the lack of such risk management
policies has been the lack of means to predict climate conditions with sufficient
skill and lead-time.
Major advances in our understanding of the Mediterranean climate have been
made in recent years. Atmospheric scientists can now predict some of the
medium-term features (one or two seasons ahead) of our climate reasonably
well. This allows forecast information to be incorporated into water management
strategies, especially those related to irrigation. The regional studies focus on
optimising traditional production systems as these dominate agricultural
production in the Mediterranean, but the research also has benefits for largescale commercial systems.
The adoption of mechanisms to effectively communicate climate information will
allow regional planners to reduce the devastating effects of drought and the
uncertain effects of climate and weather. Integrated climate monitoring
(incorporating information about climate, soil, water supply and potential
crop yields) is an important element of adaptation strategies. Information should
be in the public domain so that the level of risk can be assessed and
informed decisions about the future can be made.
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