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The Mediterranean region under climate change

 | 
Jean-Paul Moatti
, 
Stéphane Thiébault

Part 3. Adaptation, resilience, conservation of resources and prevention of risk

Chapter 5. Land degradation and climate change

What challenges?

Jean-Luc Chotte

Résumé

This chapter sets out to present a short review of (i) the general context of land degradation under the framework of UNCCD – the international convention on desertification with a specific focus on Land Degradation Neutrality, and (ii) examples of the main processes responsible for soil degradation (e.g. surface crusting, runoff and water erosion, tillage erosion, wind erosion, and salinization), along with the principles of desertification control and land rehabilitation, in light of the socioeconomic context and ecological conditions and processes. It also focuses on two other key considerations for land restoration: the conservation/increase of soil carbon stocks (see Tunisian example), and the biological restoration of functioning soil through the management of mycorrhizal fungi.
Although there is plentiful scientific evidence for strategies to prevent land degradation and/or restore degraded land, new knowledge is needed to step up the fight against land degradation and allow Mediterranean ecosystems to deliver appropriate sustainable services. This chapter cites examples of these scientific gaps (e.g. sensitivity of soil organic matter to temperature increases, the dynamics of inorganic carbon and deep soil organic, and the most effective Plant-AM in ensuring the success of restoration programmes).

L’objectif de ce chapitre est de présenter un bref aperçu i) du contexte général de dégradation des terres dans le cadre de la Convention des Nations unies sur la lutte contre la désertification avec un accent particulier sur la dégradation neutre des terres, et ii) quelques exemples des principaux processus responsables de la dégradation des sols (par exemple, l’encroûtement de surface, les eaux de ruissellement et de l’érosion de l’eau, l’érosion du travail du sol, l’érosion éolienne, salinisation), et les principes de lutte contre la désertification et la réhabilitation des terres, compte tenu des conditions et des processus écologiques, et le contexte socio-économique. De plus, ce chapitre met en lumière deux autres aspects pour la restauration des terres qui sont le maintien/l’augmentation des stocks de carbone du sol (voir l’exemple des stocks des sols en Tunisie) et la restauration biologique du fonctionnement des sols par la manipulation des champignons mycorhiziens.
Bien que les preuves scientifiques sont déjà disponibles pour aider les stratégies visant à prévenir la dégradation des terres et/ou à restaurer les terres dégradées, de nouvelles connaissances sont nécessaire pour intensifier les moyens de lutte contre la dégradation des terres et permettre aux écosystèmes méditerranéens de répondre aux enjeux de développant durable. Ce chapitre aborde quelques exemples de ces fronts de science (sensibilité des matières organiques des sols à l’augmentation de la température, dynamique du carbone inorganique, et du carbone stocké dans les horizons de profondeurs, choix des plantes et de leur hôte mycorhiziens adaptés aux conditions locales, valorisation des ressources végétales locales...).

Texte intégral

Introduction: adaptation, resilience, conservation of resources and prevention

1Under the framework of UNFCCC, the Paris agreement (December 2015), in place of the almost expired Kyoto Protocol, aims to limit the increase of the global temperature to below 2 °C. Article 2.1 stresses the need “to strengthen the global response to the threat of climate change, in the context of sustainable development efforts to eradicate poverty”, including actions aimed at “increasing the ability to adapt to adverse impacts of climate change and foster climate resilience and low greenhouse gas emission development, in a manner that does not threaten food production.” The need to pursue mitigation and adaptation in tandem is therefore widely acknowledged.

2Although humankind has always adapted to diverse weather and climate conditions using a wide range of practices (irrigation, water management, crop diversification, etc.), there is an urgent need to take action to consolidate and accelerate adaptation strategies, particularly in agriculture. This need is borne out by the following factors (Howden et al. 2007):

  • A 0.1 °C increase in world temperature during the past decade,
  • More rapid than expected climate change because of increases in greenhouse gas (GHG)
  • Lack of agreement for the reduction of GHG emissions.
  • 1 «The propensity or predisposition to be adversely affected» (IPPC, 2014)

3Although adaptation has different meanings in ecology, climate policy and evolutionary biology (see Glossary IPPC, 2014), a broad definition would be “an adjustment to actual and expected climate conditions to reduce the risk and vulnerability of ecosystems and society and to seek opportunities to cope with climate change”. Adaptation strategies must be formulated in response to well identified risks and vulnerabilities1. Two main categories of adaptation can be identified:

  • Ecosystem-Based Adaptation (EBA) is the use of biodiversity and ecosystem services as part of an overall strategy to help people adapt to the adverse effects of climate change (SCBD, 2009),
  • Community-Based Adaptation (CBD) refers to the participatory identification and implementation of community-based development activities that strengthen the capacity of local people to adapt to climate change (see in Archer et al. 2014).

4Africa is the world’s second most populous continent after Asia. Most African regions have faced an increase in extreme temperature (Seneviratne et al. 2012). Toward the end of the century, heat waves and extreme temperatures will increase whereas – except in East Africa – projected heavy precipitation will not increase. Observed and projected data lack sufficient scope.

5Africa as a whole is the most vulnerable continent due to its high exposure and low adaptive capacity. Because of the lack of observations, the detection and attribution of observed climate change in Africa to anthropogenic emissions is not sufficiently clear-cut (Niang et al. 2014). This therefore reduces the effectiveness of any adaptive strategy, although action is urgently needed. Agriculture – the main economic domain in terms of employment –has witnessed stagnant yields relative to the population growth (FAO, 2002). Recent improvements (2000-2010) have not impacted significantly on the overall pattern, since they have been recorded from the lowest productive countries. Reliance on rainfed crop production (98% of the production relied on rainfed crops un SSA), high intra-and inter-seasonal climate variability, recurrent droughts or floods and persistent poverty limit the capacity to adapt. Africa’s food production is therefore at risk. Simulations of main crop yields point to the consistently negative effect of climate change on major cereal crops in Africa. A study by Eid et al. (2007) stressed the high vulnerability of wheat production in North Africa. The temperature increases in West Africa are estimated to counteract the positive impact of rainfall increase (Sultan et al. 2013).

6Climate uncertainties, lack of real-time and future climate projections, and complex interacting barriers at local, national and international levels need to be addressed to build long term and multi-scale adaptive plans for actions. The National Adaptation Plan for Action (NAPA) and the Comprehensive African Agriculture Development Program (CAADP) highlight the political will to enrich economic growth through agriculture. CAADP focuses on four pillars: land and water management, market access, food supply and hunger and agricultural research (NEPAD, 2010). For Africa, reduced crop productivity has been identified as one of nine key regional risks (Niang et al., 2014).

7Research has demonstrated that no single adaptation can meet the needs of all communities in Africa. Moreover, adaptation and mitigation must be integrated in policy. For agriculture, sustainable land management techniques are particularly vital for Africa. This chapter explores the situation with a particular focus on soil functioning. It sets out to present a short review of (i) the general context of land degradation under the framework of UNCCD–the international convention on desertification with a specific focus on Land Degradation Neutrality, and (ii) examples of the main processes responsible for soil degradation (e.g. surface crusting, runoff and water erosion, tillage erosion, wind erosion, and salinization), along with the principles of desertification control and land rehabilitation, in light of the socioeconomic context and ecological conditions and processes. It also focuses on two other key considerations for land restoration: the conservation/increase of soil carbon stocks (see Tunisian example), and the biological restoration of functioning soil through the management of mycorrhizal fungi.

Bibliographie

References

Archer E.R.M., Oettlé N.M., Louw R., Tadross M.A. 2008
Farming on the edge in arid western South Africa: climate change and agriculture in marginal environment. Geography, 93(2), 98-107.

Eid H.M., El-Marsafawy S.M., Ouda S.A. 2007
Assessing the Economic Impacts of Climate Change on Agriculture in Egypt: A Ricardian Approach. Policy Working Paper 4342, Development Research Group, Sustainable and Urban Development Team, The World Bank, Wahsington, DC, USA, 33pp.

Howden S.M., Soussana J-F., Tubiello F.N., Chletri N., Dunlop M., Meinke H. 2017
Adapting agriculture to climate change. PNAS 104, 19691-19696.

NEPAD, 2010
The Comprehensive Africa Agriculture Development Programme (CAADP) in Pratice; Highlighting the Success. Commissioned by the The NEPAD Planning and Coordinating Agency (NEPAD-Agency) and Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH and implemented through the Overseas Development Institute (ODI), NEPAD Agency, Addis Ababa, Ethiopia, 39pp.

Niang I., Ruppel O.C., Abdrado M.A., Essel A., Lennard C., Padgham J., Urquhart P., 2014
Africa. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects, Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate on Climate Change [Barros, V.R., C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCraken, P.R. Mastrandrea, L.L. White (eds.)] Cambridge University Press, Cambrigde, UK and New York, NY USA, pp 1199-1265.

SCBD (Secretary of the Convention on Biological Diversity), 2009
Connecting Biodoversity and Climate Change: Repport of the Second Ad Hoc Technical Expert Group on Biodiversity and Climate Change. CBD, UNEP, Montreal, Canada.

Seneviratne S.I., Nicholls N., Easterling D., Goodess C.M., Kanae S., Kossin J., Luo Y., Marengo J., McInnes K., Rahimi M., Reichstein M., Sorteberg A., Vera C., Zhang X. 2012
Changes in climate extremes and their impacts on the natural physical environment In: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A special Report of Working Groups I and II of the Intergovernmental Panell on Climate Change [Field, C.B., Barros, T.F. Stocker, D. Dokken, K.L. Ebi, M.D. Mastrandrea, K.J. Mach, G.-K. Plattner, S.K. Allen, M. Tignor, and P.M. Midgley (eds.)]. Cambridge University Press, Cambrigde, UK and New York, NY USA, pp 109-230.

Sultan B., Roudier P., Quirion P., Alhassane A., Muller B., Dingkuhn M., Ciais P., Guimberteau M., Traore S., Baron C. 2013
Assessing climate change impacts on sorghum and millet yields in the Sudanien and Sahelian savannas of West Africa. Environmental Research Letters, 8 (1), 14-40

Notes

1 «The propensity or predisposition to be adversely affected» (IPPC, 2014)

© IRD Éditions, 2016

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