Desertification
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SPM3 Desertification Coordinating Lead Authors: Alisher Mirzabaev (Germany/Uzbekistan), Jianguo Wu (China) Lead Authors: Jason Evans (Australia), Felipe García-Oliva (Mexico), Ismail Abdel Galil Hussein (Egypt), Muhammad Mohsin Iqbal (Pakistan), Joyce Kimutai (Kenya), Tony Knowles (South Africa), Francisco Meza (Chile), Dalila Nedjraoui (Algeria), Fasil Tena (Ethiopia), Murat Türkeş (Turkey), Ranses José Vázquez (Cuba), Mark Weltz (The United States of America) Contributing Authors: Mansour Almazroui (Saudi Arabia), Hamda Aloui (Tunisia), Hesham El-Askary (Egypt), Abdul Rasul Awan (Pakistan), Céline Bellard (France), Arden Burrell (Australia), Stefan van der Esch (The Netherlands), Robyn Hetem (South Africa), Kathleen Hermans (Germany), Margot Hurlbert (Canada), Jagdish Krishnaswamy (India), Zaneta Kubik (Poland), German Kust (The Russian Federation), Eike Lüdeling (Germany), Johan Meijer (The Netherlands), Ali Mohammed (Egypt), Katerina Michaelides (Cyprus/United Kingdom), Lindsay Stringer (United Kingdom), Stefan Martin Strohmeier (Austria), Grace Villamor (The Philippines) Review Editors: Mariam Akhtar-Schuster (Germany), Fatima Driouech (Morocco), Mahesh Sankaran (India) Chapter Scientists: Chuck Chuan Ng (Malaysia), Helen Berga Paulos (Ethiopia) This chapter should be cited as: Mirzabaev, A., J. Wu, J. Evans, F. García-Oliva, I.A.G. Hussein, M.H. Iqbal, J. Kimutai, T. Knowles, F. Meza, D. Nedjraoui, F. Tena, M. Türkeş, R.J. Vázquez, M. Weltz, 2019: Desertification. In:Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems [P.R. Shukla, J. Skea, E. Calvo Buendia, V. Masson-Delmotte, H.-O. Pörtner, D.C. Roberts, P. Zhai, R. Slade, S. Connors, R. van Diemen, M. Ferrat, E. Haughey, S. Luz, S. Neogi, M. Pathak, J. Petzold, J. Portugal Pereira, P. Vyas, E. Huntley, K. Kissick, M. Belkacemi, J. Malley, (eds.)]. In press. 249 Chapter 3 Desertification Table of contents Executive summary ..................................................................................... 251 3.7 Hotspots and case studies ........................................................ 292 3.7.1 Climate change and soil erosion ................................ 292 3.1 The nature of desertification ................................................. 254 3.7.2 Green walls and green dams ........................................ 294 3.1.1 Introduction ............................................................................ 254 3.7.3 Invasive plant species ........................................................ 297 3.1.2 Desertification in previous IPCC 3.7.4 Oases in hyper-arid areas in the and related reports ............................................................. 256 Arabian Peninsula and northern Africa .................. 300 3.1.3 Dryland populations: 3.7.5 Integrated watershed management ......................... 302 Vulnerability and resilience ........................................... 256 3.1.4 Processes and drivers of desertification 3.8 Knowledge gaps and key uncertainties ......................... 305 under climate change ....................................................... 258 Frequently Asked Questions ................................................................ 306 3.2 Observations of desertification ........................................... 260 FAQ 3.1: How does climate change 3.2.1 Status and trends of desertification ......................... 260 affect desertification? .................................................................. 306 3.2.2 Attribution of desertification ........................................ 265 FAQ 3.2: How can climate change 3 induced desertification be avoided, 3.3 Desertification feedbacks to climate ............................... 268 reduced or reversed? ..................................................................... 306 3.3.1 Sand and dust aerosols .................................................... 268 FAQ 3.3: How do sustainable land 3.3.2 Changes in surface albedo ............................................. 269 management practices affect ecosystem services and biodiversity? ......................................................... 306 3.3.3 Changes in vegetation and greenhouse gas fluxes ...................................................... 270 3.4 Desertification impacts on natural and References .......................................................................................................... 307 socio-economic systems under climate change ...... 270 3.4.1 Impacts on natural and managed ecosystems .. 270 3.4.2 Impacts on socio-economic systems ........................ 272 3.5 Future projections ............................................................................ 276 3.5.1 Future projections of desertification ........................ 276 3.5.2 Future projections of impacts ....................................... 278 3.6 Responses to desertification under climate change ................................................................... 279 3.6.1 SLM technologies and practices: On-the-ground actions ..................................................... 279 3.6.2 Socio-economic responses ............................................. 283 3.6.3 Policy responses .................................................................... 285 Cross-Chapter Box 5 | Policy responses to drought ............................................................................................... 290 3.6.4 Limits to adaptation, maladaptation, and barriers for mitigation ............................................. 291 250 Desertification Chapter 3 Executive summary confidence), leading to soil organic carbon decline in some dryland areas. {3.1.1, 3.2.2, 3.5.1, 3.5.2, 3.7.1, 3.7.3} Desertification is land degradation in arid, semi-arid, and dry sub-humid areas, collectively known as drylands, resulting Risks from desertification are projected to increase due to from many factors, including human activities and climatic climate change (high confidence). Under shared socio-economic variations. The range and intensity of desertification have pathway SSP2 (‘Middle of the Road’) at 1.5°C, 2°C and 3°C of global increased in some dryland areas over the past several warming, the number of dryland population exposed (vulnerable) to decades (high confidence). Drylands currently cover about 46.2% various impacts related to water, energy and land sectors (e.g., water (±0.8%) of the global land area and are home to 3 billion people. stress, drought intensity, habitat degradation) is projected to reach 951 The multiplicity and complexity of the processes of desertification (178) million, 1152 (220) million and 1285 (277) million, respectively. make its quantification difficult. Desertification hotspots, as While at global warming of 2°C, under SSP1 (‘Sustainability’), the identified by a decline in vegetation productivity between the exposed (vulnerable) dryland population is 974 (35) million, and 1980s and 2000s, extended to about 9.2% of drylands (±0.5%), under SSP3 (‘Fragmented World’) it is 1267 (522) million. Around half affecting about 500 (±120) million people in 2015. The highest of the vulnerable population is in South Asia, followed by Central numbers of people affected are in South and East Asia, the Asia, West Africa and East Asia. {2.2, 3.1.1, 3.2.2, 3.5.1, 3.5.2, 7.2.2} circum Sahara region including North Africa and the Middle East including the Arabian Peninsula (low confidence). Other dryland Desertification and climate change, both individually and in regions have also experienced desertification. Desertification combination, will reduce the provision of dryland ecosystem has already reduced agricultural productivity and incomes (high services and lower ecosystem health, including losses in confidence) and contributed to the loss of biodiversity in some biodiversity (high confidence). Desertification and changing dryland regions (medium confidence). In many dryland areas, climate are projected to cause reductions in crop and livestock spread of invasive plants has led to losses in ecosystem services productivity (high confidence), modify the composition of plant (high confidence), while over-extraction is leading to groundwater species and reduce biological diversity across drylands (medium 3 depletion (high confidence). Unsustainable land management, confidence). Rising CO2 levels will favour more rapid expansion particularly when coupled with droughts, has contributed to of some invasive plant species in some regions. A reduction in the higher dust-storm activity, reducing human well-being in drylands quality and quantity of resources available to herbivores can have and beyond (high confidence). Dust storms were associated with knock-on consequences for predators, which can potentially lead to global cardiopulmonary mortality of about 402,000 people in disruptive ecological cascades (limited evidence, low agreement). 2005. Higher intensity of sand storms and sand dune movements Projected increases in temperature and the severity of drought are causing disruption and damage to transportation and solar events across some dryland areas can increase chances of wildfire and wind energy harvesting infrastructures (high confidence). occurrence (medium confidence). {3.1.4, 3.4.1, 3.5.2, 3.7.3} {3.1.1, 3.1.4, 3.2.1, 3.3.1, 3.4.1, 3.4.2, 3.4.2, 3.7.3, 3.7.4} Increasing human pressures on land, combined with climate Attribution of desertification