Dossiers

thématiques du CSFD

Dossiers tagged with: desertification

Carbon in dryland soils
Carbon in dryland soils Multiple essential functions
10
2014
40 pp

Abstract

Soil organic carbon (SOC) has a key role in the overall behaviour of soils and agroecosystems. Increasing its content enhances soil quality and fertility, thus improving agricultural resilience and sustainability and, in turn, food security of societies. Soils also contain the largest pool of carbon interacting with the atmosphere. Agricultural and forestry systems that reduce atmospheric carbon concentrations by sequestering this carbon in biomass and in soil organic matter are carbon sinks. Combating desertification contributes to soil carbon sequestration, thus mitigating global warming, while contributing to sustainable agricultural management.

Soils have only recently become a global environmental issue, especially in the framework of three international environmental conventions. These conventions have interrelated issues, especially with respect to dryland regions—desertification, climate change and biodiversity loss. Few tangible policies have, however, been drawn up concerning carbon in dryland regions. The impact of agricultural, pastoral and forestry activities on the carbon cycle need especially to be taken into greater account.

In the current carbon market system, carbon volumes of agricultural and forestry sectors are low as compared to those of other sectors (industry, etc.). Moreover, these markets do not fully recognize all activities that are conducive to carbon sequestration in agricultural soils, particularly in drylands. Carbon markets have so far been focused on checking amounts of carbon sequestered, whereas it would be much easier, and verifiable, to directly promote recognized ‘carbon sequestering’ practices. Such a market could provide much more efficient operational leverage for modifying agricultural practices and setting up systems to protect soils in dryland regions.

Combating desertification
Combating desertification Through direct seeding mulch-based cropping systems (DMC)
4
2006
40 pp

Abstract

Water and soil are the first links of the food chain of ecosystems, and these components in turn nurture the soil with their biomass. Desertification affects both of these key components with a series of consequences that ramify throughout the entire ecosystem, which thus becomes vulnerable, loses part of its biodiversity and hence its resilience and functions. These degraded ecosystems are no longer able to provide stakeholders— especially farmers—with resources and services. Farmers are then forced to overutilize the environment, thus further worsening the desertification process. What could be done to offset this desertification spiral at local and then at higher global scales?

Research and development on cropping systems such as direct-seeding mulch-based cropping systems (DMC) means at least partially meeting this challenge, and then disseminating this technique in Southern countries during the 21st century. DMC is a highly innovative system, central to conservation agriculture and agro-ecological practices. It involves no-till cropping and provides permanent soil protection with both crop residue and companion crops, through crop combinations, yearly sequences or rotations.

 Pastoralism in dryland areas
Pastoralism in dryland areas A case study in sub-Saharan Africa
9
2013
60 pp

Abstract

Often barren natural rangelands are directly utilized for pastoral livestock farming, which is by nature mobile (transhumance). This activity is on the rise in sub-Saharan Africa, providing a living for a great number of herders, generating marketable animal products, while also supporting pastoral-oriented societies.

Pastoral livestock farming prevails especially in dry tropical regions. The livestock farming techniques are continuously adjusted to adapt to extremely variable local conditions, i.e. the spatial distribution of resources (fodder, water) or sanitary, social and economic situations. Pastoralism is a source of meat, even for export, and has an important role in the agricultural economy of Sahelian countries. This activity enhances social stabilization and peace in marginal dryland areas.

Pastoralism is becoming difficult in sub-Saharan Africa despite these advantages, especially due to the recent worsening of climatic conditions. Collective rangeland grazing rights are not legally recognized and protected sufficiently to stave off the problem of crop farming expansion and landgrabbing by investors. Sub-Saharan pastoralism has considerably evolved to cope with this situation—increase in transhumance into new areas, partial settling of herding families and income diversification.

Cattle grazing modifies the long-term evolution of rangeland ecosystems (soil, vegetation, biodiversity), but these impacts also have some advantages (soil fertility transfer, seed dispersal, maintenance of natural environments). Environmental degradation, which in extreme cases leads to desertification, is usually the result of localized overtapping of resources or poor management. The causes of this degradation must be assessed since it is ultimately detrimental to pastoralism.

The conditions required for sustainable pastoralism generally depend on the public policies of each concerned country and current legislation. Professional pastoral farmers are getting organized and international organizations are beginning to take stock of the economic and ecological challenges concerning pastoralism for the future.

Fighting wind erosion
Fighting wind erosion One aspect of the combat against desertification
3
2011
44 pp

Abstract

Wind erosion—alone or combined with other physical or socioeconomic causes—is a mechanism that may induce desertification, i.e. severe or irreversible degradation of water and soil resources. Now that this phenomenon is better understood, the model of the 1970s based on three distinct stages (causes, mechanisms, consequences) has been discarded, in view of the many feedbacks and insidious links generated by wind erosion. Timely detection of wind erosion onset thresholds with remote sensing tools (satellite images and aerial photographs), and spatial delimitation and positioning of the phenomena observed are essential to be able to efficiently combat the damaging effects of wind erosion. No field operations can be effective without prior knowledge of wind erosion mechanisms at the land-atmosphere interface.

At this interface, wind activities are organised in dynamic units on a continental scale, or so-called global wind action systems (GWAS) spanning the Saharan and Sahelian regions, or regional scale (sweeping southwards across Egypt), or so-called regional wind action system (RWAS), in which humans interact via their activities. A GWAS is divided into three (particle source, wind transport, deposition) areas, each of which may be found at several locations within the GWAS.

When striving to combat wind-induced threats, especially by controlling clay, silt and sand particle loss and, conversely, sand invasion, the sediment balance and types of prevailing dunes should be taken into account, while distinguishing between the:

  • mobility in source areas where mobile particles should be stabilised
  • mobility in transport areas where wind streams should be deflected so as to prevent human infrastructures from being filled with sand, and
  • mobility in deposition areas where sand invasion is at stake.

The first stage consists of defining the site to be protected in relation to the GWAS or RWAS (taking the topography and type of dune or mobile sand into due consideration), and assessing the surface to be stabilised or protected. The second operational stage aims at reducing the surface wind velocity through technical and biological strategies.

To ensure success, the specific features of local ecosystems and human communities must be taken into consideration and effectively tapped in wind erosion control programmes in order to minimise costs and come up with solutions that are viable for the communities involved. 

A land degradation assessment and mapping method
A land degradation assessment and mapping method A standard guideline proposal
8
2010
52 pp

Abstract

Arable land is a vital resource for humankind. Cultivation of this land generates food to meet the daily needs of the world’s population. This land is limited and the area is constantly shrinking—2 ha/inhabitant in 1900 versus 0.4 in 2010— due to the impact of human activities and population growth. Arable land is not a naturally renewable resource on the time scale of human evolution and is invaluable as it cannot be manufactured. This land therefore has to be properly managed. It is thus essential to understand the actual land degradation status so as to be able to draw up protection, restoration and/or sustainable management policies.

In 1990, the results of the first global land assessment were incomplete because of a lack of common assessment procedure. This CSFD Dossier describes a streamlined land degradation assessment method that can be applied on different spatial scales—farm to country—and in all climatic zones in worldwide.

The type, extent and degree (or severity) of land degradation are the three main indicators selected. When pooled, they represent a degradation index rating that is displayed in a simple way on maps that can be readily used by politicians, decisionmakers and the media. Complementary indicators are useful for staff responsible for implementing land degradation control initiatives in areas earmarked by decisionmakers: degradation rate and trend, historical background, soil sensitivity and resilience, possible causes, off-site effects, and rural population density.

The results obtained could contribute to meeting the objectives of the United Nations Convention to Combat Desertification, especially through national objectives in countries affected by desertification that must regularly report on land degradation.

Remote sensing
Remote sensing A tool to monitor and assess desertification
2
2005
44 pp

Abstract

Remote sensing is a technique that enables to observe the radiation scattered or emitted by the Earth surface. Satellite-based remote sensing allows regular, repetitive, accurate observations of nearly the whole planet, at various spatial and temporal scales, in several wavelength fields.

Such observations render the nature, state, temporal and spatial variations of the properties of the objects at the Earth surface. By way of example, water-covered areas, roughness, soil moisture, changes in the nature of land, density and phenological evolution of the vegetation cover, sand winds, are information included in these observations. Nevertheless, these observations usually combine together, making them more or less difficult to extract from the raw data transmitted by satellites. The science of remote sensing consists in interpreting and processing the series of spatial and temporal images in order to extract such parameters, qualitatively or quantitatively. Desertification is a phenomenon of irreversible land degradation. It results from complex processes linked to the coupled and joint evolution of natural and human-induced factors. The beginning, development and results of such processes are materialised by land surface states and their evolution.

Remotely sensed data consequently include information that the science of remote sensing allows to partly extract with more or less accuracy. Such information coupled with others are involved in various stages of the desertification process. Remote sensing provides useful data; some of them are essential information impossible to collect otherwise (especially in terms of homogeneity and spatial coverage and/or temporal monitoring) for early warning, monitoring the development of desertification phenomena and acknowledging a final state. Among others, remote sensing may allow to determine the impacts of policies to combat desertification. However, because of the mentioned limits regarding the extraction of useful parameters and the part played by the latter in the processes concerned, remote sensing turns out to be a tool among others - certainly a powerful one, but not a scientific, decisional or operational “miracle” solution.

After presenting in detail the technique and science of remote sensing and how it allows to monitor various elements of desertification processes, this brochure deals with the most important and significant cases and brings both aspects together. Several key parameters and processes are studied: roughness, albedo, surface temperature, moisture, vegetation indices on the one hand; vegetation cover monitoring, modifications in the land surface composition in dry environments, wind transportation on the other hand. Examples are developed: evolutions of specific sites, projects under way. Lessons taught by previous experiments are critically analysed, options for the future are designed.

Restoring natural capital in arid and semiarid regions
Restoring natural capital in arid and semiarid regions Combining ecosystem health with human wellbeing
7
2009
40 pp

Abstract

The overall aim of this CSFD thematic report is to communicate, share and discuss key elements of restoring natural capital in arid and semiarid regions. Its main goal is to promote the implementation of this approach within societies and communities that are the most threatened by desertification.

The regions threatened by desertification cover about 40% of the emerged land masses. Most people living in these regions are exposed to poverty or extreme poverty. An approach to simultaneously restore degraded ecosystems and improve human wellbeing is urgently needed.

Biodiversity conservation, poverty alleviation and economic development are traditionally perceived as having separate or even conflictual interests. This report shows the contrary. Indeed, restoring natural capital combines ecological restoration and sustainable development objectives in order to create a synergy between them both and also the maintaining of native biodiversity.

Several sites throughout the world in arid or semiarid areas are discussed to illustrate elementary concepts of natural capital restoration in the field. This report is the result of the literature review of the available scientific material relevant to natural capital restoration in arid and semiarid areas. Most of the definitions and field illustrations are adapted from Aronson, Milton and Blignaut (2007), a book written by 71 international scientists, managers and journalists in the fields of ecology, economics and ecological economics.  

Support

Editing, production and distribution of Les dossiers thématiques du CSFD are fully supported by this Committee thanks to the support of relevant French Ministries and AFD (French Development Agency).

  • Ministère de l'Education nationale, de l'Enseignement supérieur et de la Recherche
  • Ministère des Affaires étrangères et du Développement international
  • Ministère de la Transition écologique et solidaire
  • Agence Française de Développement (AFD)

Opinions

The opinions expressed in these reports are endorsed by the Committee.

Contact

CSFD
Comité Scientifique Français de la Désertification
Agropolis International
1000 avenue Agropolis
F-34394 Montpellier CEDEX 5 •  France
Tel.: +33 (0)4 67 04 75 73• email: csfd@agropolis.fr

Log in

Log in


Website by Olivier Piau (Agropolis Productions) - Webmaster: Laurence Monin (Agropolis International)
© 2013-2015 Comité Scientifique Français de la Désertification (CSFD)

Dossiers

thématiques du CSFD

Mankind is now confronted with an issue of worldwide concern, i.e. desertification, which is both a natural phenomenon and a process induced by human activities. Our planet and natural ecosystems have never been so degraded by our presence. Long considered as a local problem, desertification is now a global issue of concern to all of us, including scientists, decision makers, citizens from both developed and developing countries. Within this setting, it is urgent to boost the awareness of civil society to convince it to get involved. People must first be given the elements necessary to better understand the desertification phenomenon and the concerns. Everyone should have access to relevant scientific knowledge in a readily understandable language and format.

Within this scope, the French Scientific Committee on Desertification (CSFD) has decided to launch a series entitled Les dossiers thématiques du CSFD, which is designed to provide sound scientific information on desertification, its implications and stakes. This series is intended for policy makers and advisers from developed and developing countries, in addition to the general public and scientific journalists involved in development and the environment. It also aims at providing teachers, trainers and trainees with additional information on various associated disciplinary fields. Lastly, it endeavours to help disseminate knowledge on the combat against desertification, land degradation, and poverty to stakeholders such as representatives of professional, nongovernmental, and international solidarity organisations.

These Dossiers are devoted to different themes such as global public goods, remote sensing, wind erosion, agroecology, pastoralism, etc, in order to take stock of current knowledge on these various subjects. The goal is also to outline debates around new ideas and concepts, including controversial issues; to expound widely used methodologies and results derived from a number of projects; and lastly to supply operational and academic references, addresses and useful websites. These Dossiers are to be broadly circulated, especially within the countries most affected by desertification, by email, through our website, and in print. Your feedback and suggestions will be much appreciated!

Scientific editing and iconography: Isabelle Amsallem, Agropolis Productions
Design and production: Olivier Piau, Agropolis Productions