Desertification is the degradation of land in arid and dry sub-humid areas, resulting primarily from man-made activities and influenced by climatic variations. It is principally caused by overgrazing, overdrafting of groundwater and diversion of water from rivers for human consumption and industrial use, all of these processes fundamentally driven by overpopulation. A major impact of desertification is biodiversity loss and loss of productive capacity, for example, by transition from land dominated by shrublands to non-native grasslands. In the semi-arid regions of southern California, many coastal sage scrub and chaparral ecosystems have been replaced by non-native, invasive grasses due to the shortening of fire return intervals. This can create a monoculture of annual grass that cannot support the wide range of animals once found in the original ecosystem. In Madagascar's central highland plateau, 10% of the entire country has been lost to desertification due to slash and burn agriculture by indigenous peoples. In Africa, if current trends of soil degradation continue, the continent will be able to feed only 25% of its population by 2025, according to UNU's Ghana-based Institute for Natural Resources in Africa. Globally, desertification claims a Nebraska-sized area of productive capacity each year.

1. The Horn of Africa experiencing serious drought
Twenty million people face starvation, particularly in Kenya to Somalia and Ethiopia
There was no violence, not even a threat, but the situation is self-explanatory. At the turn of the trail
that winds through the arid Isiolo in northern Kenya, men dressed in Shuker (Blanket) coming out of the
bush use without asking permission in the water tank a company working on road construction.
The group of pastors Samburu is exhausted. The men were thirsty, very thirsty, and they are determined
to fill their jerry cans in the small tank valve. In the dry plains, the wind carries the columns of dust above
the trees dry and dead animals. “Some of us have more than twenty miles to find this water. It has lost
90% of our cows. We only want to die,” said Jefferson Leparsanti, jaws clenched, leaning on his lance.
Either d „water is prohibited, there is more grass around. The rivers are dry. Here is the region of death. “
The point of the nearest water, a place of desolation called Lerat, contains a few muddy liquid. Shephe-
rds, without a word, look at a dying cow fell a few steps, skeleton dressed in skin. Since when this drought
lasts she? Opinions differ. Oxfam cites a figure of five years. “Climate change in this region does not nec-
essarily mean less rain, in fact, if we can provide something here that is a slight increase in rainfall in the
coming decades. But the rain should be more concentrated and brutal, with intervals drier and more
flooding, “said Alun McDonald, spokesman for the NGO which has launched an appeal for ten million euros
to help people.

2. Oxfam believes that in seven countries, from Kenya to Djibouti, 23 million people are affected by drought.
The United Nations estimates the number of people now dependent on food aid in the Horn about twenty
million, with half the Somali population (3.6 million). The drought is not the only cause. In Kenya, the
price of staple foods has doubled, while the country continued to export grain. Massive diversions have
affected the stocks of grain from the government. However, while periods of drought were separated by
intervals of ten years, the cycle is accelerating: 2000 and 2005, when the herds were decimated, and
2009, with low precipitation.
In the vicinity of Mount Kenya, a hundred miles farther south, flocks to succeed on the road every few
hundred meters, the content along the axis through the barbed wire that led everywhere. A program to
slaughter cows was established by the government. Trucks are loaded animals in the north to bring them
to slaughter only domestic, near Nairobi. On arrival, unload heaps of corpses, animals are too weak to
withstand the road. In total, an estimated quarter of a million head of cattle has undertaken one of the
largest mass migration in recent decades. Some come from Ethiopia, marched two months, three months.
Inevitably, conflicts arise here and there.
Towards Isiolo, 300 kilometers from Nairobi, the first violence between groups were reported in January.
Fifteen dead. Turkana, Somali, Pokot, Samburu, ethnic groups are caught in cycles of attacks and reprisals
against the backdrop of traditional raids to steal livestock. At the exit of Isiolo, Jalal Aideed, youngest son
of a Somali family farmers, no longer dares visit his field to the periphery. “There are Shift (bandits) Tur-
kana there. If they see me, they kill me.”

3. Heavy rain accompanied by rainfall can devastate infrastructure.
The day before, two Turkana were killed by Somalis, in retaliation for an attack Turkana few days earli-
er. On the other side of town, Jalal Aideed may instead go to the family ranch: 3 000 acres (about 1 200
hectares), more than a thousand cattle and five men to protect the destitute from the plain thirst for
preventing access to water the field. These inequalities further increase the crisis.
The scarcity of resources does not provided an automatic escalation of tensions. With the influx of men
and herds, violence broke out on occasion. In many cases, negotiated solutions are sought. Question of
wisdom about survival.
But these mechanisms are weak. The population has doubled in twenty years in the region. And erratic
rainfall combined with the destruction of Kenya‟s forests, disrupting groundwater, causing a drop in river
levels. In the Baringo area, large landowners to political power have been digging deep wells to irrigate
their vast fields of grain. Two steps, farmers saw their animals die of thirst.
Now another danger threatens the region. After drought, torrential rains. The weather phenomenon El
Nino, according to the Kenyan Meteorological Services should start in October and be accompanied by
rainfall can devastate infrastructure. “We have made contingency plans for more than 100 000 people,
storing food for example,” said Patrick Lavand‟homme, Office of Humanitarian Coordination (OCHA). The
High Commissioner for Refugees (UNHCR) provides food stocks near the refugee camps in Kenya, some of
which will be displaced due to floods.
“Above all, said Patrick Lavand‟homme, the rains will arrive in finding people who have just suffered their
third or fourth consecutive year of drought, and are in distress.”
Jean Phillipe Rémy

4. Sand Stoms in East Africa
Because of global warming?
It is comfortable for the mind to wander its lens on the globe and climate change attributed to weather
disasters in series: devastating drought in East Africa, floods in the Sahel … What do the rainfall records
performed in these regions for a little over fifty years?
The answer may surprise. “In West Africa, for example, the rainfall was high in the 1960s, then was
known sequences in very dry years 1970 and 1980, says climatologist Serge Janicot. Since the 1980s, we
witnessed a surge while remaining below the average secular. But it perceives the signal a return to condi-
tions more favorable rainfall in this region. “
This oscillation between dry spells and wet sequences is not to be attributed to climate change. “Pre-
sumably it is the result of natural variability in the system,” said Mr. Janicot. Work published this summer
suggest that precipitation of this region are influenced by the oscillations of the North Atlantic.
It fluctuates slowly, with a period of fifty or sixty years ago, between periods of warm and cold phases.
So, the question for this region is not so much whether this happens is related to climate change, but ra-
ther to what extent it will affect the great natural cycles uncovered by researchers. That question is
open.
The various models used in the work of the Intergovernmental Panel on Climate Change (IPCC) does not
agree. Some of these simulations predict that climate change will lead to a drying of sub-Saharan Africa,
others predict it the other way around.

5. Global Warming Concern
Cette oscillations de séquences sèches et de séquences humides n'est pas à mettre au compte du
changement climatique. « On peut penser qu'elle est le résultat de la variabilité naturelle dy système »,
estime M. Janicot. Des travaux rendues publics cet été suggèrent que des précipitations de cette région
du monde subissent l'influence des oscillations de l'atlantique Nord.
Celui-ci fluctue lentement avec une période de cinquante ans à soixante ans environ, entre des phases
chaudes etd es phases froides. Du coup, la question qui se pose pour cette région n'est pas de savoir si ce
qui advient est lié au changement climatique.
Mais plutôt dans quelle mesure celle ci va influencer sur les grand cycles naturels mis au jour par les
chercheurs. Cette question-là est ouverte.Les différents modèles numériques utilisés dans le cadre des
travaux du groupe d'experts intergouvernemental sur l'évolution du climat (GIEC) ne s'accorde pas.
Certaines de ces simulations prévoient que le changement climatique induira un assèchement de l'Afrique
Subsaharienne, d'autre lui prédisent l'inverse.
Stephane Foucart