D. M. Stafford Smith

A synthesis of recent global change research on pasture and rangeland production: reduced uncertainties and their management implications

There is significant uncertainty about the effects of global change on the vegetation and animal productivity of pasture and rangeland ecosystems. This paper presents a synthesis of progress made between 1994 and 1999 in the Global Change and Terrestrial Ecosystems (GCTE) Pastures and Rangelands Core Research Project 1 (CRP1) network, a world-wide network of 83 full-time equivalent researchers established in different pasture and rangelands systems to reduce these uncertainties. The network focuses on key processes controlling forage and animal production at a paddock/landscape scale, in order to improve the ability to model animal production. To date, the network has resulted in a considerable reduction in the uncertainties about the effects of elevated CO2 on growth, and to a lesser extent composition and forage quality, of intensive pastures in cool, wet climatic zones. However, knowledge of other grazed ecosystems and processes is more limited. The greatest confidence is in predicting implications for vegetation production, with lesser confidence in implications for vegetation composition, animal production and adaptation options. Overall, the stimulatory effect of double ambient CO2 on grassland production averages about C17% in ecosystem-based experiments. This is less than previous estimates. Individual system responses to elevated CO2 can vary widely and are predicted to be higher in moisture-limited and warm-season grassland systems. Species composition change is likely to be an important mechanism altering grassland production and its value for grazing livestock, especially in drier rangelands with woody shrub invasion. On average, the legume content of productive grass‐legume swards is increased by C10% due to CO2 enrichment. Leaf nitrogen reductions due to elevated CO2 are often observed but are generally modest compared with effects of other management factors. New data collection efforts should be focused in areas of the world which are most sensitive to food security issues and most subject to global change, in particular humid semi-arid margins and subtropical grasslands. There remains no good basis for extrapolating findings between different pasture and rangeland systems. This synthesis indicates that greater focus is required on the linkages between the biophysical, social and economic factors that will influence future changes in pasture and rangeland ecosystems and their implications for food security.

The stewardship of arid Australia : ecology and landscape management

tag=1 data=The stewardship of arid Australia : ecology and landscape management. by S.R. Morton, D.M. Stafford Smith, M.H. Friedel, G.F. Griffin and G. Pickup tag=2 data=Morton, S.R.%Stafford Smith, D.M.%Friedel, M.H.%Griffin, G.F.%Pickup, G. tag=3 data=Journal of Environmental Management, tag=4 data=43 tag=5 data=3 tag=6 data=March 1995 tag=7 data=195-217. tag=8 data=LAND%ENVIRONMENT tag=9 data=ECOLOGICALLY SUSTAINABLE LAND MANAGEMENT tag=13 data=IND

Risk, Biology and Drought Management Strategies for Cattle Stations in Central Australia

A simulation study was conducted to explore the effects of drought on financial returns for three different grazing strategies for arid zone beef cattle properties in central Australia. RANGEPACK Herd-Econ, a commercially available herd and property economic model was used to compare the strategies in all possible 10-year sequences of good, average and dry years, to examine the effect of drought period on post drought recovery, and to run the strategies through a historical sequence based on the last 100 years of rainfall data. The management strategies, based on real properties corrected to the same resource base, compared an “average” 3000 AU † property, a “low-stock” 2000 AU property with high and resilient herd biological rates and a “high-stock” 4000 AU property which manages drought conditions by quick destocking tactics. For the full probability distribution of all possible 10-year sequences, the mean accumulated cash surpluses were £1·98m., £2·28m. and £1·34 m. for the average, high-stock and low-stock management strategies respectively. Both average and high-stock had highly variable financial returns whereas low-stock maintained relatively constant levels. Both average and high-stock recovered quickly from 1-year droughts, but low-stock started to have higher annual returns when droughts lasted 2 years or longer. In the examination of the last 100 years, both average and high-stock would have been bankrupted on todays costs in the 1956–1965 decade, whereas low-stock would have survived with only a small deficit. The mean 10-year accumulated cash surpluses for the 10 historical decades were £1·79m., £2·1m. and £1·28 m. for the average, high-stock and low-stock strategies. This compares well with the results of the full probability distribution. Taxation rates and interest costs can interact to modify the results of this study. Normal rates of taxation and interest applied to the yearly cash surpluses tend to favour the low-stock strategy and its constant moderate cash flows. However, if business management can reduce taxation rates, and attract government support in dry years, then there are income advantages for both the average and the high-stock strategies. All stocking strategies were assumed to be sustainable. In real life, low-stock continues to improve its rangeland resource while high-stock and average are relatively stable, both with some scrub encroachment due to lack of prescribed fire. The average strategy has probably the greatest risk of environmental degradation because of its “wait and see” attitude to drought management.

Australian rangelands as complex adaptive systems: A conceptual model and preliminary results

Abstract Models to support decisions on rangeland policy must address the close links between ecological, economic, and social processes, and the adaptation of participants through time. We used an agent-based modeling approach to implement a parsimonious conceptual model of rangelands that included biophysical processes central to the functioning of rangelands, commercial enterprises, and institutions. The model operated on a monthly time step, and used economic and biophysical conditions to stimulate changes in management policies and learning. Our simple model reproduced the general patterns of forage growth and livestock dynamics in north-east Australia, and results illustrate consequences of interactions between environmental heterogeneity and learning rate.

Assessing the historical frequency of drought events on grazing properties in Australian rangelands

Abstract Using a simulation model of sheep and cattle grazing systems in different regions of the Australian rangelands, we tested the use of different measures and analyses for identifying an ‘exceptional circumstances’ drought event, defined as occurring once in 20 years in the long term. Over the century-long simulations, all measures (rainfall, various soil moisture measures, pasture growth, liveweight gain and an economic productivity index) identified the major drought periods in each region. However, the measures differed considerably in the identification of marginal events, because economic and biological hardship are not always synchronised. Total soil moisture seems to be the best single measure, providing it is properly calculated, but there is a strong case for considering more than one measure. Periods perceived as exceptional are also greatly affected by the choice of averaging technique, moving window, and assumptions about baseline management strategies. Hence the choice of index has implications for sustainability. We also show that revocation criteria are as important as the criteria for declaring a drought, and discuss the difficult balance between objectivity and equity.

The Australian Collaborative Rangelands Information System: preparing for a climate of change

Change is a constant in Australia’s rangelands. Appropriate management of this change requires a sound knowledge of drivers (e.g. climate variability, livestock grazing), their impacts on natural resources (state and trend), socio-economic outcomes, and how these feed back through learning and adaptive management to affect drivers and their impacts. Information is required at scales from enterprise to national, with regional and broader level information serving to influence rangelands governance through institutional arrangements, policy and funding programs. The Australian Collaborative Rangelands Information System (ACRIS) collates and analyses data from national sources and from its State and Territory jurisdictional partners to track and understand change at regional to national scales. ACRIS has recently reported changes between 1992 and 2005 in several biophysical and socio-economic themes at bioregional resolution. This paper describes the processes used to collate and analyse the often disparate data, to synthesise information across data types and to integrate emergent higher order information across drivers, impacts and outcomes to provide more complete understanding of change. Data gaps and inconsistencies were a major challenge, and we illustrate how some of these issues were addressed by using indicators to report changes in biodiversity. ACRIS now needs to foster increased coordinated monitoring activity and develop its reporting capacity to become the valued information system for Australia’s rangelands. We propose that future improvements will be best structured within a hierarchically nested framework that provides consistent overarching data at national scale relevant to the variety of rangeland values (e.g. change in ground cover) but focuses on regionally-relevant ecosystem services, and their appropriate measures, at the regional scale. A key challenge is to implement consistent and systematic methods for monitoring biodiversity within this hierarchical framework, given limited institutional resources. Finally, ACRIS needs to develop a dynamic web-based delivery system to enable more frequent and flexible reporting of interpreted change than is possible through periodic published reports.

A comparison of development options on a Northern Australian beef property

Abstract A comparison of eight improved management technologies was made for a typical Northern Australian beef cattle property carrying about 3000 breeding cows located in the Katherine district of the Northern Territory. RANGEPACK HerdEcon, a computer package which links a dynamic herd model with farm enterprise costs, was used to progressively implement various property development strategies. These included combinations of cow and steer supplementation, and pasture improvement with Stylosanthes spp. Over a 20-year period the predicted accumulated cash surplus for the superior cow herd supplementation, cow and steer herd supplementation, and pasture improvement options were

Integrating models of soil dynamics, animal behaviour and vegetation response for the management of arid lands

0·66m,

The bioeconomic implications of various drought management strategies for a communal cattle herd in the semi‐arid savanna of KwaZuIu‐Natal

1·12m and

A framework for the ecology of arid Australia

1·32m respectively. After real interest rates of 6% were charged on borrowed capital and company taxation was levied, however, the 20-year net surpluses were