Patterns of accessing variable resources across time and space: Desert plants, animals and people

Key resources in and and semi-arid systems are highly variable in time and space. Biophysical variability is mainly driven directly or indirectly by rainfall. Arid-dwelling people are also exposed to variability indirectly from their biophysical environments, and directly as a result of sparse, mobile populations and variable, distant signals from policy and markets. The tradeoffs between the benefits and costs of increasing the scale of resource use are comparatively more critical in shaping system dynamics in and systems than mesic environments. Understanding the strategies employed to scale resource use is vital for arid-system management. We contribute to this discussion using a conceptual model, based on modern portfolio theory, to explore how variability is managed by diversifying access to resources across space and time. The model is developed using ecological ideas and our Australian case knowledge, but demonstrates general learning on how optimal investment in strategies changes with resource distribution, and with the physical characteristics of the entity (e.g. plant, animal) and resource (e.g. water, nutrients) in question. Using pastoral enterprise, arid-system administration and policy cases, we argue that people and organisations need variability-coping strategies that are comparable with biophysical responses, and that strategy behaviour needs greater acknowledgement in managing arid systems. (C) 2008 Elsevier Ltd. All rights reserved.