Theme: RAINFALL AND LAND DEGRADATION IN GUINEA-BISSAU

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Theme RAINFALL AND LAND DEGRADATION IN
GUINEA-BISSAU

• IMPACTS ON CLIMATE CHANGES

Superior Technical in Meteorological Instruments-
Luís Cá E-mail luis.ca19_at_yahoo.fr - General
Direction of Meteorology - July/2010
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PRESENTATION PLAN

• I. ABSTRACT
• II. INTRODUCTION
• III. LAND DEGRATATION
• IV. RAINFALL ANALYSIS FOR LAND DEGRADATION
  ASSESSMENT
• V. APPLICATION OF THE ANNUAL SCALE FTRENDS AND
  PROBABILITIES

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I. ABSTRACT

• Among the components of land degradation are
  desertification, soil degradation and erosion. In
  any discussion of land degradation there are four
  spatial-temporal scalesthat should be
  distinguished regional, watershed, field and
  point. At each scale, one may use different
  proxies for land degradation. In order to study
  land degradation at multiple scales it is also
  necessary to study rainfall at multiple scales.
  Rainfall can be analysed for land degradation at
  four different scales from the small annual
  scale to the large minute scale. Besides scales
  one may also distinguish between average values
  and temporal and spatial variations. In this
  paper, one of more examples of rainfall data are
  presented for each scale and interpreted with
  respect to land degradation. At the annual scale,
  trend analysis and rainfall probabilities are
  important. The decadal(10 days) scale is
  especially suitable for calculating the varying
  lengths of the growing season. At the scale of
  one day, the size classes of showers, return
  period (design storm), hydrological and agronomic
  modelling and dry spell analysis are discussed.

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ABSTRACT (Cont.)

• The concepts of land degradation mitigation are
  derived from the rainwater balance. After drawing
  a number of conclusions, it is suggested how we
  could improve our understanding of land
  degradation by improving the availability of
  rainfall data at multiple scales.

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II. INTRODUTION

• Rainfall is the most important climatic factor in
  determinig areas at risk of land degradation and
  potential desertification. Rainfall plays a vital
  role in the developpment and distribution of
  plant life, but the variability and extremes of
  rainfall can lead to soil erosion and land
  degradation. If unchecked for a period of time,
  this land degradation can lead to
  desertification. The interaction of human
  activity on the distribution of vegetation though
  land management practices and seemingly benign
  rainfall events can make land more vulnerable to
  degradation. These vulnerabilities become more
  acute when the prospect of climate change is
  introduced.
• Land is the complex of soil, water and the
  natural flora and fauna in a landscape, above and
  below the soil surface. Land degradation is the
  decline in the extent too which land yields
  products useful to local livelihoods(Scoones and
  Toulmin 1999) or, in more recent terminology, in
  the decline in ecosystem services(MEA 2005).
  The complexity of the notions land and land
  degradation and their scale features lead to
  many different definitions.

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INTRODUTION (CONT.)

• A special form of land degradation is
  desertification, land degradation in the arid,
  semi-arid and dry sub-humid areas most vunerable
  to land degradation. The previous UN
  Secretary-General Kofi Annan has called
  desertification one of the worlds most alarming
  processes of environmental degradation. Under the
  scenario of climate change it is often claimed
  that the droughts, flash floods, dust storms,
  famine, migration and forest fires associated
  with desertification are bound to increase,
  leading to loss in human well-being and bringing
  high socio-economic costs.That long-term food
  productivity is threatened by land degradation is
  of major significance and concern, since this has
  serious impact on global food security.

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III. LAND DEGRATATION

• Definition land degradation
• All current land degradation definitions refer to
  loss in productivity of the land (Blaikie and
  Brookfield 1987). This implies that one of the
  possible proxies for land degradation is a
  decline in productivity of the land. Soil
  degradation, being a component of land
  degradation, comprises erosion and the decline in
  soil qualities chemical changes due to leaching
  or salinisation, physical changes due to
  compaction or crusting, and biological changes
  due to the loss of soil organic matter or
  micro-organisms. With respect to erosion, it is
  useful to distinguish between on-site and
  off-site erosion.
• Recently a new definition has been proposed,
  based on the concept of ecosystem services(MEA
  2005). Furthermore, many have taken on board the
  notion expressed by Warren(2002) that land
  degradation is contextual and cannot be judged
  independently of its spatial, temporal, economic,
  environmental and cultural context.
• So, at present there are too many definitions for
  land degradation. In fact it may be questioned
  whether changes in land or land qualities that
  result from deliberate changes in land use, for
  instance due to economic development, may be
  called land degradation.

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IV. RAINFALL ANALYSIS FOR LAND DEGRADATION
ASSESSMENT

• In order to study land degradation at multiple
  scales it is necessary to study rainfall at
  multiple scales too. Rainfall can be analysed for
  land degradation at four different scales from
  the small annual scale to the large minute
  scale. Each scale has its specific
  application(s). Besides scales, one may also
  distinguish between average values and temporal
  and spatial variations. A few examples of
  rainfall data for each of the scales are
  presented below and interpreted with respect to
  land degradation.

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V. APPLICATION OF THE ANNUAL SCALE TRENDS AND
PROBABILITIES

• Trends of annual rainfall are used to assess
  changes in rainfall that affect land degradation
  mainly through changes in vegetation cover.
  Conway et al. (2004), analysing 100 years of
  rainfall in Addis Ababa, conclude that there was
  no major shift or trend in annual and seasonal
  rainfall during the period 1898 2002.
  Well-known drought years in northern and
  northeastern Ethiopia are not picked out in the
  Addis Ababa rainfall record, suggesting that the
  series should not be used as a proxy for
  inter-annual rainfall variability in these parts
  of the Ethiopian highlands.
• The annual rainfall of the 3 major stations in
  Guinea-Bissau with a long-term record. The result
  is shown in Figures.

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Station of Bafatá - Northwest of Guinea-Bissau

• INTENTTION OF LOWER

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Station of Bissau-Observatory North and Center
of Guinea-Bissau

• SMALL LOWER

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Station of Bolama South of Guinea-Bissau

• STABLE

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Station of Bafatá - Northwest of Guinea-Bissau
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Station of Bissau-Observatory North and Center
of Guinea-Bissau
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Station of Bolama South of Guinea-Bissau
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• THANKS FOR ATTENTION