Evolving
Contexts of the Desertification Debate <back>
A
great many debates have grown up around the notion of desertification
as a process of degradation that affects the arid, semiarid and
subhumid zones of the globe. A fundamental and continuing debate
has been over whether desertification actually exists and, if
so, how it might be defined, measured and assessed. Rather than
simply review the evolution of these debates we examine the contexts
in which they take place and how those contexts have contributed
to the evolution of our understanding of the intertwined processes
that contribute to desertification. The fact that these “contexts”
have changed over time, and that some of these contexts are often
ignored have helped sustain debate. We consider four “contexts”
that frame much of the debate and consider what impact each has
had: (1) changes in our understanding of climate variability;
(2) changes in our understanding of vegetation responses to perturbation;
(3) changes in our understanding of social processes, including
household responses to economic perturbation; and (4) changes
in our understanding of desertification as a political process
or artifact.
Policy
implications of the Sahelian recovery <back>
The Sahelian greening is
one phase in a continuous sequence of wet and dry periods. This
paper examines policies in the light of these changes. It looks
both at policies involved both in other greenings and in the Sahel
itself. The others include Sinai, southern Russia, Arizona and
the Loess Plateau in northern China. In Sinai, the policies that
brought about greening include exclusion, emigration and nature
conservation. In Russia, the policy that had impact was the collapse
of the Soviet collective farm system. In Arizona, it came after
the Taylor Grazing Act of 1934 which allowed the US Forest Service
to manage grazing. On the Loess Plateau, it has been the result
of irrigation, tree-planting, the extension of responsibility
of land users and perhaps aerial seeding and fencing. Most of
these policies are inapplicable to the Sahel, with the possible
exception of some of the Chinese measures.
In the Sahel, some policies in Burkina Faso, and elsewhere did
enable soil and water conservation projects, but the success of
these projects is more due to the harnessing of local skills.
More generally, policy has had little to do with the greening
(as with the earlier browning), even though the Sahel has been
a seething cauldron of policy debate for three decades.
Sahelian environmental policies face two main challenges: fast
and occasionally extreme fluctuations in rainfall; and changes
in the scientific dialectic. There should be less emphasis on
the negative policy of controlling land degradation, and more
on positive policies that encourage adaptation and allow for rapid
deployment to make use of good years and insurance policies against
bad ones.
Greening
of the Sahel <back>
For
the last four decades there has been sustained scientific interest
in contemporary environmental change in the Sahel. It suffered
several devastating droughts and famines between the late 1960s
and early 1990s. Speculation about the climatology of these droughts
is unresolved, as is speculation about the effects of land clearance
on rainfall and about land degradation in this zone. However,
recent findings suggest a consistent trend of increasing vegetation
greenness in much of the region. It is not possible to explain
the vegetation trend by rainfall only. The paper presents empirical
data and discusses possible other causes of this trend such as
land use change, migration and armed conflicts. The policy implications
of a positive trend in biophysical conditions are also discussed.
One conclusion of the findings is that more site-specific information
on the interaction of biophysical dynamics (climate, soils, vegetation)
and farming systems (farming practices and risk management strategies)
is needed in order to better understand and ultimately support
the development challenge in the Sahel.
The
impact of soil and water conservation on agriculture and environment
on the northern part of the Central Plateau of Burkina Faso between
1980 and 2001 <back>
In
the beginning of the 1980s the situation on the northern part
of the densely populated Central Plateau was dramatic: drought
years succeeded each other, food shortages at household level
were endemic and the environment had become degraded. The commonly
held view is that the process of environmental degradation continued
in the second half of the 1980s as well as in the 1990s.
A
study was recently undertaken by a multidisciplinary team of national
researchers, who looked at long-term changes in agriculture and
environment in this region. Most of their research findings show
positive trends. Cereal yields have increased by about 50% since
1984-88; in two of the three provinces studied the cultivated
area remained stable during the last 15 years; tree density and
species diversity are higher on fields treated with soil and water
conservation than on untreated fields; livestock numbers have
increased and livestock management is evolving from extensive
to semi-intensive and a survey in 59 villages shows that, according
to the villagers, local groundwater levels have improved substantially
since the start of soil and water conservation. Based on criteria
used by villagers, which are mainly related to levels of household
food security, rural poverty seems to have decreased significantly
(up to 50%) in villages with soil and water conservation.
Much
has been achieved, but much more remains to be done. It is urgent
to improve soil fertility on cultivated land and to fight against
land degradation on uncultivated land, which continues unabated.
23
years of Sahelian vegetation dynamics from NOAA-AVHRR <back>
Satellite
measurements of the global biosphere in the form of the normalized
difference vegetation index (NDVI) have generated a 23 year time
series appropriate for the studies seasonal to interannual vegetation
dynamics of the Sahel region. The close coupling between Sahelian
rainfall and the green-up of vegetation has made it possible to
utilize this vegetation index data set as a proxy for the land
surface response to climate variability. Examination of the this
time series principally reveals two major periods: (a) 1982-1993
marked by below average vegetation and persistence of drought
with a signature large scale drought during the 1983-1985 period;
and (2) 1994-2003, marked by a trend towards “greener”
conditions with region-wide above normal vegetation conditions
in 1994. Spatial patterns enable us to conclude that is not a
footprint of desertification, rather they indicated the variability
of green vegetation biomass over the region in response to interannual
variations in rainfall. Systematic studies of changes on the landscape
at local scales using high spatial resolution satellite data sets
such as those from LANDSAT, SPOT and MODIS will allow for an improved
documentation of degradation of Sahelian land resources that could
lead to desertification.
Using
farmers’ responses to change as a guide to policy at the
country level <back>
The
dominant narrative influencing Sahelian environmental policy during
the past 30 years has been that of ‘desertification’.
This narrative is disaggregated into (a) the sub-themes of ‘deforestation’,
‘overstocking’, ‘overcultivation’ and
over-use of water, (b) sub-hypotheses, which create expectations
about farmers’ NRM as an agent of degradation, and (c) biophysical
outcomes which have been measured, mapped or assessed. The expectations
created by the sub-hypotheses are compared with evidence from
selected districts in three countries (Diourbel Region in Senegal,
Maradi Department in Niger, and the Kano region of northern Nigeria).
Long-term data sets (1960-2000) collected at district level and
ground-truthed with village level investigations (1999) are used.
The performance of the production systems in these districts departs
in significant ways from hypothetical expectations, giving grounds
to query their validity, and to construct a counter-narrative.
The findings of these studies (carried out in collaboration with
30 scientists in the countries concerned) have been synthesised
with a view to deriving policy lessons for dryland development.
A simple narrative of ‘desertification’ is inadequate
for understanding the flexibility, adaptability and diversity
of farmers’ responses to change, and fails to identify the
potential for productivity increases, income and welfare improvements.
NRM as a whole should be understood within a context of livelihood
management, and is therefore strongly influenced by macro-economic
policy. Generalised properties of a new dryland development policy
approach are outlined. Using the lessons learnt from the research
and in subsequent dissemination activities, burning issues that
have specific application to Sahelian drylands are identified
for policy formation at the country level.
UNCCD
perspectives on the changes in the Sahel <back>
The
plight of the Sahel was brought squarely on the international
arena by the reports on the debilitating drought of the early
seventies, after massive loss of life and property. The international
community made attempts to address the issues of drought and desertification
by the establishment by UNCOD in 1977, of the well-known Plan
of Action, but the efforts fell way short of expectation.
The
UNCED process and the resultant Chapter 12 of Agenda 21 led to
further reflection, but there was felt a strong need for a legally
binding instrument. The birth of the UNCCD, the Convention to
address the fight against drought and desertification the world
over, was the way out. This was a call for paradigm shift, a different
way of dealing with the twin problems of drought and desertification.
The
“United Nations Convention to Combat Desertification in
Those Countries Experiencing Drought and/or Desertification, Particularly
in Africa”, with its entry into force in December of 1996,
to date has 190 signatories. The thrust of the UNCCD is for concerted
local level action, but with international level support and partnership.
The
objective of the UNCCD is “to combat desertification and
mitigate the effects of drought…..through effective action
at all levels, supported by international co-operation and partnership
arrangements, in the framework of an integrated approach which
is consistent with Agenda 21, with a view to contributing to the
achievement of sustainable development in affected areas.
The UNCCD recognizes that achieving this objective will involve
long-term integrated strategies that focus simultaneously, in
affected areas, on improved productivity of the land and the rehabilitation,
conservation, and sustainable management of land and water resources,
leading to improved living conditions, in particular at the community
level.
The Sahel is a major entry point in understanding and eventually
addressing the seemingly complex problems of recurrent droughts
and the ever-present desertification and land degradation. The
particular attention given to Africa by the UNCCD includes the
Sahel, as testimony to the dire need to take concrete action in
that region.
Various
interacting forces come into the picture, in influencing not only
the natural processes, but also the possible remedial measures.
Traditional knowledge and coping strategies of the affected peoples,
early warning systems, the role of the prescribed tools - the
Convention implementation frameworks, climatic factors, ecological
factors, anthropogenic factors, are all important components to
be taken into consideration when looking at the “Changes
in the Sahel”. The combined action of these at local level,
national level as well as appropriate international interventions
in one way or another hold the key.
Monitoring
vegetation growth and mapping changes in landscape : Senegal case
study <back>
A
lack of early warning system in the early 1970s prevented governments
and even researchers of having a good appreciation of the droughts
occurred, in particular in 1972, in semi-arid zones.
Since this period, developing tools to monitoring vegetation growth
and to estimate available feeding for cattle has been a strong
concern for decision makers. The Centre de Suivi Ecologique (CSE)
has experienced, in such a context, the development of various
products. Decadal NDVI information and annual biomass maps using
NOAA/AVHRR and Spot/Vegetation data are some of the products successfully
elaborated and regularly published since 1987.
More recently, some other indicators like VCI and SPI have been
successfully applied to drought monitoring in Senegal.
The process has allowed to set up a NOAA database of well calibrated
images. These data have been used to look at the tendency of the
vegetation growth at national level.
At a more localized level, several studies based on satellite
images and aerial photos from 1960’s until 2000 have been
conducted to map changes occurred in landuse and land cover. CSE
is still continuing to work on this kind of studies with FAO in
the framework of the Land degradation assessment project. It is
aiming to identify hot and brigth spots and to document their
causes using mapping and and censuses.
Early warning systems are now used in some Sahelian countries
on a more operational basis and can be expanded to all Sahelian
countries. Detection of changes in Sahel landscape is doable at
large and localized areas (access to high resolution data still
needs to be improved). Generalization on very large areas should
be done carefully.
Long-term
precipitation variability in the Sahel <back>
The
Sahel has undergone tremendous fluctuations of rainfall throughout
historical times. Extreme and prolonged droughts are an inherent
feature of the environment. The fluctuations have been particularly
extreme during the last half of the 20th century. The mean rainfall
for 30-year periods, the traditional time period for a climatic
“normal”, decreased 25% to 40% in the Sahel between
1931 – 1960 and 1968 – 1997. the contrast is even
greater when the wettest and driest decades, the 1950s and 1980s,
are compared. During those decades, the entire continent was affected.
That clearly demonstrates that the main causes of rainfall variability
are to be found in the large-scale general atmospheric circulation.
These in turn are at least partially driven by sea-surface temperature
variability, however El Nino/La Nina does not play a large role.
Most of the change takes place in August. Wet/dry conditions in
the Sahel tend to be associated with a northward/southward displacement
of the rainbelt over West Africa. In some cases, however, the
reduction in rainfall is associated with an overall weakening
of the tropical rainbelt. There is little relationship between
the amount of rainfall during the season and length of the season
or its onset date. These facts have strong implications for both
adaptive strategies and predictability.
The persistent dry conditions prevailed from the late 1960s through
the mid-1990s. TRMM satellite data that was validated with a dense
gauge network showed that the region became markedly wetter in
1998. Relatively good rainfall continued through the next year.
As a whole rainfall of the last 6 years has been better than average,
but the “wet” conditions of the 1950s were not matched.
Regional
variability, local relative degradation; how to manage the scales
<back>
«
Desertification » has to be clearly distinguished from «
desert encroachment », which is linked with the romantic
idea of a desert (erg and reg) encroaching irreversibly upon green
areas. Different thresholds of land and soils degradation have
been used to assess the lost of natural resources, and differ
considerably according to the idea of « irreversibility
» of the ultimate stage of degradation (which is the «
desertification » on a 25 years basis). We have no evidence
to say that the drought period has ended, neither we can say that
there is a global trend towards a drier climate since the last
century. So that the « greening Sahel », following
the « yellowing Sahel » of the 70’s is just
an expression of this climate variability : the desert did not
(already) encroached upon the arid Sub-Saharian regions.
Are land use changes (towards less range pastures, more fields
and fallow fields, less time of fallowing, etc) responsible or
not for soil and land degradation cannot be assessed just through
a global survey at regional scale: the degradation (loss of soil
material, decreasing in production) depends notably upon the way
populations are using their space and resources (human density,
technology, etc.).
Examples from North Saharian countries, where animal pressure
increased during the drought period, due sometimes to national
actions taken to mitigate the effect of the drought, show that
we have to differentiate between « land degradation and/or
desertification » (which correspond to the loss of production
capability) and « resources degradation », which express
a decreasing in man-useful resources.
Combining bio-physical and socio-economical assessment and monitoring,
combining functional models at local scale and structural monitoring
at national or regional scale, could help understanding the trends
in desertification. These are the objectives of the ROSELT/OSS
programme.
Environmental
and land cover changes in the Sahel region: lessons learned, Challenges
and priority actions <back>
During
the last three decades the Sahel region has been confronted with
various forms of environmental and ecological degradation due
to climate change and anthropogenic factors. These changes have
been described as the most important that the region had ever
faced. Recent studies and analysis show spatial and temporal patterns
changes and variability in the landscape features, tree-crop patterns
and forest cover, with severe degradation of soils and fragile
ecosystems.
However, their impacts could have been mitigated or even reversed
through conducive policies and concerted and collaborative efforts
with focus on priority areas where the conservation and rehabilitation
of fragile lands could be the most cost effective.
The FAO LADA team is carrying out, since 2002, studies focused
on the assessment of the status and trends of these changes, including
their impacts on livelihoods and identification of hotspots. LADA
work aims to generate up-to-date information related to ecological
and environmental changes, including economical, social and technical
aspects, traditional knowledge and practices on land management
which have occurred in drylands during these last decades.
The principle objective of the LADA project is to develop methods
and tools to assess and quantify the nature, extent, severity
and impacts of land degradation on ecosystems, watersheds and
river basins, carbon storage and biological diversity in drylands
at a range of spatial and temporal scales.
The project will also build national, regional and global assessment
capacities to enable the design and planning of interventions
to mitigate land degradation and establish sustainable land use
and management practices.
Mitigation
of Impacts of Changes in Sahel <back>
In
the frame of the partnership of weather, climate and environment
for development, meteorological applications usefully contribute
to mitigate the impacts of climate variability and changes in
Sahel.
For
this purpose, the products of seasonal and intra-seasonal climate
forecast disseminated to end-users (rural communities and others)
by RANET multi-media system are currently usefully used in Niger
and Mali.
By
seasonal and intra-seasonal climate prediction process forecasts,
outlooks and climate summary are produced to predict and monitor
early or late onset or withdrawal of rainfall, the dry or set
spells and outlook of the rainy season. This information is disseminated
in due time to end-users to enable them to better manage their
socio-economic activities.
These
tailored products are carried out through two specific programs
on these matters by ACMAD in collaboration with its partners (National
Meteorological Services, sub-regional and international specialized
center). The interdisciplinary teams use them on the ground.
So
for the benefit of Sahelian population the program on seasonal
and intra-seasonal climate prediction and the program on dissemination
of the products of meteorological application to rural communities
in their mother tongue are providing useful tools. These programs
should be strengthened and generalized in the Sahel.
A
new land cover classification system for desertification assessment,
mapping and monitoring <back>
To
date there is no consensus concerning the definition of desertification
and as such there is no agreement regarding the current status
of desertification in the world as a whole or in its various areas.
Lack of consensus is mainly due to the fact that the proposed
definitions have no measurable parameters for desertification
assessment and mapping. In spite of lack of consensus on the definition
of desertification, it is generally recognized that desertification
is a marked decline or total loss of the potential ability of
the ecosystem in dry lands to sustain the biological productivity
of land. According to the World Bank definition, desertification
is a process of sustained land (soil and vegetation) degradation
in arid, semi-arid and dry sub-humid areas, caused at least partly
by man. It reduces production potential to an extent that can
neither be readily reversed by removing the cause, nor easily
reclaimed without substantial investment (World Bank, 1988). Many
studies have shown that changes in vegetation/land cover and land
use patterns form important criteria in land degradation/desertification
assessment, mapping and monitoring. It has further been demonstrated
that changes in land cover over time can be monitored effectively
using remotely sensed satellite data. However, due to the existence
of numerous and inconsistent land cover classification systems,
it is not possible to optimally use new or existing land cover
data in land degradation/desertification assessment and monitoring
and in planning of sustainable land use systems. To address this
problem, there is a need to come up with an internationally accepted
land cover classification system. This is particularly important
due to increasing availability of vast amount of remotely sensed
land cover data that is collected from earth observation satellites
on a regular basis. The Food and Agriculture Organisation of the
United Nations (FAO)/United Nations Environmental Program (UNEP)
Land Cover Classification System (LCCS), which attempts to address
this problem, is briefly discussed in this paper as well as its
possible use in land degradation/desertification assessment, mapping
and monitoring.
The
utilization of geoinformation technology for agroenvironmental
applications in Egypt <back>
Remote
sensing can provide valuable and timely information about natural
resources and environment which are very important for sustainable
development. However, in developing countries, the utilization
of such advanced technologies differs from one country to another.
Egypt, as a developing country, has experience in the utilization
of earth observation satellites and aircraft remote sensing data
in soil mapping as well as assessment of land degradation.
Agriculture in Egypt depends mainly on artificial irrigation,
which has long been practiced since the pre- historic times by
the Egyptians, and still used today in nearly the same manner.
The main source of irrigation water in Egypt is the Nile water.
Despite a number of projects to regulate the Nile having been
implemented, much of the Nile water is still in use in a non-
scientific way with an efficiency of irrigation of less than 50%
and salinization as a consequence. The change from the unwise
use of irrigation water to the exactly calculated amounts of different
crops requirement of water will save a great amount of water besides
conserving soils from rendering saline.
In all the cultivated areas the natural vegetation has been degraded
as a result of man’s activities or has been completely removed.
Agriculture has long been practiced in the Nile Delta by the ancient
Egyptians, and so natural vegetation can only be found in the
northern part of the Delta and the desert. The rest of the Delta
and Wadies are grown with different economic crops in a recurrent
succession (grain crops, fiber crops, legumes, sugar cane ...
etc.).