Chris J. Stokes

Fragmentation of Australian rangelands: processes, benefits and risks of changing patterns of land use

Pastoral development of Australian rangelands has been accompanied by fragmentation of land use, which has changed the scale at which humans and livestock access patchily-distributed resources in landscapes. These changes have tended to be targeted towards achieving narrowly defined policy or land management objectives, and have ignored the broader consequences for land use. We describe the processes of rangeland fragmentation, the factors that have driven these changing patterns of land use, and current trends towards enterprise consolidation and intensification, which continue to reshape the way humans and livestock use rangelands. Although there is growing interest in intensified systems of rangeland management, some of the benefits are uncertain, and there are several risks that serve as a caution against overoptimism: (i) intensification involves multiple simultaneous changes to enterprise operations and the benefits and trade offs of each component need to be better understood; (ii) if intensification proceeds without addressing constraints to implementing these management options sustainably then overutilisation and degradation of rangelands is likely to occur; (iii) further fragmentation of rangelands (from increased internal fencing) could compromise potential benefits derived from landscape heterogeneity in connected landscapes. Adaptation by the pastoral industry continues to reshape the use of rangelands. A broad-based approach to changes in land use that incorporates risks together with expected benefits during initial planning decisions would contribute to greater resilience of rangeland enterprises.

Is Proactive Adaptation to Climate Change Necessary in Grazed Rangelands

Abstract In this article we test the notion that adaptation to climate change in grazed rangelands requires little more effort than current approaches to risk management because the inherent climate variability that characterizes rangelands provides a management environment that is preadapted to climate change. We also examine the alternative hypothesis that rangeland ecosystems and the people they support are highly vulnerable to climate change. Past climate is likely to become an increasingly poor predictor of the future, so there is a risk in relying on adaptation approaches developed solely in response to existing variability. We find incremental, autonomous adaptation will be sufficient to deal with most of the challenges provided by the gradual expression of climate change in the next decade or two. However, projections of greater climate change in the future means that the responses required are qualitatively as well as quantitatively different and are beyond the existing suite of adaptation strategies and coping range. The proactive adaptation responses required go well beyond incremental on-farm or local actions. New policies will be needed to deal with transformational changes associated with land tenure issues and challenges of some displacement and migration of people in vulnerable parts of rangelands. Even where appropriate adaptation actions can be framed, issues of when to act and how much to act in a proactive way remain a challenge for research, management, and policy. Whether incremental or transformational involving system changes, a diversity of adaptation options will be required in different rangeland regions to enhance social and ecological resilience. Resumen En este articulo evaluamos la idea de que la adaptación al cambio climático en pastizales pastoreados requiere un mayor esfuerzo que lo que se hace en la actualidad para manejar los riesgos debido a la inherente variabilidad climática que caracteriza a los pastizales y que provee un manejo del ambiente que está pre-adaptado al cambio climático. Examinamos la hipótesis alternativa que los ecosistemas de pastizales y la gente que mantienen es altamente vulnerable al cambio climático. El clima pasado es probable que se convierta cada vez más en un pobre predictor del futuro así que el riesgo en confiar en enfoques de adaptación desarrollados únicamente en respuesta a la variabilidad existente. Encontramos que la adaptación autónoma será suficiente para lidiar con la mayoría de los desafíos proporcionados por la expresión gradual de cambio climático en las siguientes dos décadas. Sin embargo, las proyecciones de un mayor cambio climático en el futuro significan que las respuestas requeridas son tanto cualitativa como cuantitativamente diferentes y éstas van más allá de los alcances de las estrategias adaptación y afrontamiento. La adaptación proactiva de las respuestas requiere ir más allá del incremento de la granja o de las acciones locales. Nuevas políticas serán necesarias para lidiar con los cambios transformacionales asociados con problemas de la tenencia de la tierra y los retos del desplazamiento y migración de la gente en ciertas partes vulnerable de los pastizales. Incluso donde las medidas adecuadas de adaptación se pueden enmarcar, problemas de cómo actuar y en qué medida en una manera proactiva siguen representado un reto para los investigadores, manejadores y las políticas. Ya sea envolviendo cambios sistemáticos transformacionales o incrementales, se exigirá una diversidad de opciones de adaptación en las diferentes regiones de pastizales para mejorar las resiliencia ecológica o social.

Interacting effects of vegetation, soils and management on the sensitivity of Australian savanna rangelands to climate change

There is an increasing need to understand what makes vegetation at some locations more sensitive to climate change than others. For savanna rangelands, this requires building knowledge of how forage production in different land types will respond to climate change, and identifying how location-specific land type characteristics, climate and land management control the magnitude and direction of its responses to change. Here, a simulation analysis is used to explore how forage production in 14 land types of the north-eastern Australian rangelands responds to three climate change scenarios of +3°C, +17% rainfall; +2°C, −7% rainfall; and +3°C, −46% rainfall. Our results demonstrate that the controls on forage production responses are complex, with functional characteristics of land types interacting to determine the magnitude and direction of change. Forage production may increase by up to 60% or decrease by up to 90% in response to the extreme scenarios of change. The magnitude of these responses is dependent on whether forage production is water or nitrogen (N) limited, and how climate changes influence these limiting conditions. Forage production responds most to changes in temperature and moisture availability in land types that are water-limited, and shows the least amount of change when growth is restricted by N availability. The fertilisation effects of doubled atmospheric CO2 were found to offset declines in forage production under 2°C warming and a 7% reduction in rainfall. However, rising tree densities and declining land condition are shown to reduce potential opportunities from increases in forage production and raise the sensitivity of pastures to climate-induced water stress. Knowledge of these interactions can be applied in engaging with stakeholders to identify adaptation options.

Genetic variation in transpiration efficiency and relationships between whole plant and leaf gas exchange measurements in Saccharum spp. and related germplasm

Fifty-one genotypes of sugarcane (Saccharum spp.) or closely related germplasm were evaluated in a pot experiment to examine genetic variation in transpiration efficiency. Significant variation in whole plant transpiration efficiency was observed, with the difference between lowest and highest genotypes being about 40% of the mean. Leaf gas exchange measurements were made across a wide range of conditions. There was significant genetic variation in intrinsic transpiration efficiency at a leaf level as measured by leaf internal CO2 (Ci) levels. Significant genetic variation in Ci was also observed within subsets of data representing narrow ranges of stomatal conductance. Ci had a low broad sense heritability (Hb = 0.11) on the basis of single measurements made at particular dates, because of high error variation and genotype × date interaction, but broad sense heritability for mean Ci across all dates was high (Hb = 0.81) because of the large number of measurements taken at different dates. Ci levels among genotypes at mid-range levels of conductance had a strong genetic correlation (−0.92 ± 0.30) with whole plant transpiration efficiency but genetic correlations between Ci and whole plant transpiration efficiency were weaker or not significant at higher and lower levels of conductance. Reduced Ci levels at any given level of conductance may result in improved yields in water-limited environments without trade-offs in rates of water use and growth. Targeted selection and improvement of lowered Ci per unit conductance via breeding may provide longer-term benefits for water-limited environments but the challenge will be to identify a low-cost screening methodology.

Influencing adaptation processes on the Australian rangelands for social and ecological resilience

Resource users require the capacity to cope and adapt to climate changes affecting resource condition if they, and their industries, are to remain viable. Understanding individual-scale responses to a changing climate will be an important component of designing well-targeted, broad-scale strategies and policies. Because of the interdependencies between people and ecosystems, understanding and supporting resilience of resource-dependent people may be as important an aspect of effective resource management as managing the resilience of ecological components. We refer to the northern Australian rangelands as an example of a system that is particularly vulnerable to the impacts of climate change and look for ways to enhance the resilience of the system. Vulnerability of the social system comprises elements of adaptive capacity and sensitivity to change (resource dependency) as well as exposure, which is not examined here. We assessed the adaptive capacity of 240 cattle producers, using four established dimensions, and investigated the association between adaptive capacity and climate sensitivity (or resource dependency) as measured through 14 established dimensions. We found that occupational identity, employability, networks, strategic approach, environmental awareness, dynamic resource use, and use of technology were all positively correlated with at least one dimension of adaptive capacity and that place attachment was negatively correlated with adaptive capacity. These results suggest that adaptation processes could be influenced by focusing on adaptive capacity and these aspects of climate sensitivity. Managing the resilience of individuals is critical to processes of adaptation at higher levels and needs greater attention if adaptation processes are to be shaped and influenced.

Changing Patterns of Land Use and Tenure in the Dalrymple Shire, Australia

Australia is the world’s flattest continent, a testament to its ancient, wellweathered geological landforms, and consequently the associated soils are generally of low fertility (Flannery 1994). It is also the world’s driest inhabited continent, a situation that is exacerbated by erratic rainfall and high evaporation. In comparison with other countries, agriculture in Australia is characterized by: dependence on low productivity environments that are prone to drought and degradation; the large scale of agricultural activities; concentration on a limited range of products; heavy dependence on overseas markets; and a relatively high standard of living in the agricultural community (Laut 1988). Almost three-quarters of the country is classed as rangelands, mainly arid and semi-arid lands that are not suitable for intensive agriculture. European settlement and agricultural development of the continent, and rangelands in particular, has been marked by bitter experiences of coming to terms with the climatic and edaphic constraints of this environment. Fragmentation of Australian rangelands has been a relatively recent phenomenon. Although Aboriginal land-use practices shaped Australian

Identifying thresholds and barriers to adaptation through measuring climate sensitivity and capacity to change in an Australian primary industry

Primary producers, including graziers, crop farmers and commercial fishers are especially vulnerable to climate change because they depend on highly climate-sensitive natural resources. Adaptation to climate change will make a major difference to the severity of the impacts experienced. However, individuals (resource users) can erect sometimes seemingly peculiar barriers to potential adaptation options that need to be addressed if adaptation is to be effective. Our aim was to understand the nature of barriers to change for cattle graziers in the northern Australian rangelands. We conceptualised barriers as adverse reactions where resource users are unlikely to contemplate adaptations that threaten core values or perceptions about themselves. We assumed that resource users that were more sensitive to climate change impacts—or more dependent on the resource—were more proximate to thresholds of coping and thus more likely to erect barriers, especially people with little adaptive capacity. Given that climate sensitivity and adaptive capacity are important components of vulnerability, our approach was to conduct a vulnerability assessment to identify potential but important barriers to change. Data from 240 graziers suggest that graziers in northern Australia might be especially vulnerable to climate change because their identity, place attachment, low employability, weak networks and dependents can make them sensitive to change, and their sensitivity can be compounded by a low adaptive capacity. We argue that greater attention needs to be placed on the social context of climate change impacts and on the processes shaping vulnerability and adaptation, especially at the scale of the individual.

Hysteretic Responses to Grazing in a Semiarid Rangeland

Abstract Ecological systems comprise a complex array of interacting processes that manifest across multiple scales. Effective management of natural ecosystems has to be underpinned by an understanding of how the scaling of these processes influences system integrity and stability. This is particularly true in semiarid rangelands, which display strong relationships between pattern and process that are fundamental to maintaining ecosystem function. Grazing can disrupt the scaling of these relationships and the mechanistic coupling between pattern and process, undermining the health of grazed semiarid rangelands. This is due to possible hysteretic responses in key system components to increases and decreases in grazing disturbance. We used data from a semiarid rangeland in northern Australia to test for hysteretic responses in system components after the removal of cattle grazing. We found an uncoupling of spatial linkages between vegetation and soil moisture in a severely degraded plot that was not evident in less intensively grazed or recovering plots. Recovering plots protected from grazing for 20 yr showed a scale of spatial linkage between vegetation and soil moisture, and soil organic matter and mineralization flush, of a scale much coarser than that of degrading plots. These findings provide evidence for hysteretic recovery from grazing and demonstrate that comparison of the spatial patterns of vegetation and soil properties is essential for capturing the true state of ecological functionality in this system. This has important implications for assessing ecological function in systems typified by strong natural environmental variation or in which data for pristine conditions are lacking.