Pasture Degradation and Recovery in Australia's
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cover.qxp 15/7/04 10:01 AM Page 1 1893-1894 1894-1895 1895-1896 1896-1997 1897-1898 1898-1899 1899-1900 1900-1901 1901-1902 1902-1903 1973-1974 1974-1975 1975-1976 Edited by Greg McKeon, Wayne Hall, Beverley Henry, Grant Stone and Ian Watson 1993-1994 1994-1995 1995-1996 1996-1997 1997-1998 1998-1999 1999-2000 2000-2001 2001-2002 2002-2003 ch_prelims 28/6/04 9:37 AM Page 1 PPASTUREASTURE DDEGRADATIONEGRADATION ANDAND RRECOVERYECOVERY ININ AAUSTRALIA'SUSTRALIA'S RRANGELANDSANGELANDS Learning from History Edited by GREG McKEON WAYNE HALL BEVERLEY HENRY GRANT STONE IAN WATSON Natural Resource Sciences Queensland Department of Natural Resources, Mines and Energy 80 Meiers Road Indooroopilly Queensland Australia 4068 ch_prelims 28/6/04 9:37 AM Page 2 Dedication: We have dedicated this report to individual scientists whose work directly influenced the emerging understanding of the interaction of climate and rangeland management described here: Barry White who in 1978 showed that the impact of climatic variability on pasture, animals, cash flow and government policy could be quantified and better managed; Neville Nicholls who during the 1982 drought, showed that the El Niño – Southern Oscillation (ENSO) could be used to forecast Australian rainfall and that Australia is a land of ‘droughts and flooding rains’ because ENSO amplifies our rainfall variability; Dean Graetz who in 1984, through the television program, Heartlands, publicly highlighted past and current environmental damage; Bill Burrows who challenged the grazing industry and government to understand the ecological issues involved in rangeland use; and John Leslie and Barry Walker, who in 1986 invested in the scientific capability to deliver these emerging insights to the community and government. Department of Natural Resources, Mines and Energy, Queensland May 2004 QNRME04130 ISBN 1 920920 55 2 General Citation: McKeon, G.M., Hall, W.B., Henry, B.K., Stone, G.S. and Watson, I.W. (2004), Pasture degradation and recovery in Australia’s rangelands: Learning from History. Queensland Department of Natural Resources, Mines and Energy. General Disclaimer The information contained in this publication is intended for general use, to assist public knowledge and discussion and to help improve the sustainable management of land, water and vegetation. The information does not represent a statement of the policy of the Department of Natural Resources, Mines and Energy, Queensland. The information should not be relied upon for the purposes of a particular matter. Appropriate enquiries must be made to establish the current accuracy of the information and whether any new material is available on the subject matter; legal advice should be obtained before any action or discussion is taken on the basis of any material in this document. The Department of Natural Resources, Mines and Energy, Land and Water Australia, Australia's Rural Research and Development Corporations and their partners, Department of Agriculture Western Australia, and the authors assume no liability of any kind whatsoever resulting from any person's use or reliance upon the contents of this document. This document is produced for general information only and does not represent a statement of the policy of the Commonwealth of Australia, including the Australian Greenhouse Office and Land and Water Australia. The Commonwealth of Australia and all persons acting for the Commonwealth preparing this report accept no liability for the accuracy of or inferences from the material contained in this publication, or for any action as a result of any person's or group's interpretations, deductions, conclusions or actions in relying on this material. © The State of Queensland, Department of Natural Resources, Mines and Energy 2004 Copyright protects this publication. Except for purposes permitted by the Copyright Act 1968, reproduction by whatever means is prohibited without prior written permission of the Department of Natural Resources, Mines and Energy, Queensland. 2 PASTURE D EGRADATION AND R ECOVERY: LEARNING FROM HISTORY ch_prelims 28/6/04 9:37 AM Page 3 Foreword The publication of this report will be welcomed as an important synthesis of the history of climate and grazing in Australia’s rangelands. Several of the principal investigators are, or have been, scientists in the Queensland Department of Natural Resources, Mines and Energy. Their involvement in this national project supported by national organisations (Australian Greenhouse Office, Department of Agriculture, Fisheries and Forestry–Australia and Australia’s Rural Research and Development Corporations through the Climate Variability in Agriculture Program) reflects the Queensland Government’s commitment to stewardship of Queensland’s natural resources. There is a need for a strong stewardship responsibility by everyone involved in natural resource management. The effective use of information, science and technology provides the basis of many Departmental activities, including our work with the landholders managing the resource. The science programs undertaken within Natural Resources, Mines and Energy and other State departments in Australia demonstrate the commitment to sustaining the national pasture resource and managing for climate variability, particularly in periods of drought. The severity of the recent and current drought in regions of eastern and western Australia, including the obvious hardship for people, communities and their animals, coupled with dramatic events such as dust storms, raises the important questions of what is the current risk of degradation to the pasture resource and what role the government has in reducing that risk. This report describes the analysis of eight major degradation episodes that have occurred over the last hundred years across Australia’s rangelands. From this analysis various systems are being researched and made operational, including: • the provision of better climate risk assessment tools for graziers; • the use of pasture growth models to calculate degradation risk and safe carrying capacity; • the use of remote sensing to monitor pasture cover, and identify areas of increased risk of erosion and weed invasion; and • supporting extension material on better grazing land management options. This report provides a powerful basis for future work, and its review of the history of drought and degradation challenges us not to repeat the mistakes of the past. To use the rhetoric of the lead authors, the challenge now is to ‘prevent the next degradation episode’. Terry Hogan Director General Queensland Department of Natural Resources, Mines and Energy May 2004 PASTURE D EGRADATION AND R ECOVERY: LEARNING FROM HISTORY 3 ch_prelims 28/6/04 9:37 AM Page 4 Table of contents Acknowledgments 9 Preface 11 Authorship 13 Summary 17 Chapter 1: Historical degradation episodes in Australia: Global climate and economic forces and their interaction with rangeland grazing systems 27 1.1 Introduction 29 1.1.1 Degradation episodes and climate variability 33 1.1.2 Components of the grazing system in Australia’s rangelands 35 1.2 Changes in climate forcings from 1880 to the 1990s 37 1.2.1 El Niño – Southern Oscillation 37 ENSO-based forecasting systems 39 1.2.2 Inter-decadal Pacific Ocean oscillation 41 Other indices of inter-decadal Pacific Ocean oscillation 42 1.2.3 ENSO and IPO effects in Australia’s rangelands 43 Impact of ENSO and IPO on extended drought in degradation episodes47 Summary of ENSO and IPO effects56 1.2.4 Synoptic circulation systems 56 Northwest cloudbands 56 Behaviour of high pressure systems 57 Wind and soil erosion 57 1.2.5 Solar variability and lunar tidal influences on rangeland climate 58 1.3 Global trends in temperature, CO2 and land use change 59 1.3.1 Global warming and CO2 59 1.3.2 Climate change and the El Niño – Southern Oscillation 61 1.3.3 Land use change 61 1.4 Global economic and political forces 62 1.4.1 Wool prices 62 1.4.2 Cattle prices 64 1.5 Changes in grazing pressure 65 1.5.1 Animal genotypes 66 1.5.2 Grazing pressure and drought 67 1.5.3 Feral and native herbivores 68 Conclusion 69 1.5.4 Socioeconomic and institutional trends 69 4 PASTURE D EGRADATION AND R ECOVERY: LEARNING FROM HISTORY ch_prelims 28/6/04 9:37 AM Page 5 1.6 Mechanisms of degradation in grazed rangelands 69 1.6.1 Perennial grasslands 70 Perennial grass ‘death trap’ 71 1.6.2 Perennial shrubs 72 1.6.3 Drought and plant growth 74 1.7 Soil erosion 74 1.7.1 Processes of soil erosion 75 1.7.2 Soil erosion by wind 76 Lack of historical wind data 78 1.8 Woody weeds 80 Rabbits and woody weeds 81 Woody weeds and wind erosion 82 1.9 Recovery processes 82 The role of exclosure from grazing in recovery 83 1.10 How have grazing enterprises coped with variability? 84 1.10.1 Stock numbers and degradation 84 1.11 Conclusion 85 Chapter 2: Degradation and recovery episodes in Australia’s rangelands: An anthology 87 2.1 Introduction 88 General method of analysis of the effects of climate variability in the episodes 88 2.2 Episode 1: Western Division of New South Wales in the 1890s 89 Climate and grazing history 90 Observations and analysis 95 Recovery? 99 What do we learn for preventing land and pasture degradation? 99 2.3 Episode 2: North-eastern South Australia and western New South Wales 100 in the 1920s and 1930s Climate history 100 Data sources and chronology 101 Observations and analysis 104 Stocking rates 107 Recovery? 108 What do we learn for preventing land and pasture degradation? 110 2.4 Episode 3: Gascoyne region of Western Australia in the