Bioeconomic model of weeds in pastures

Seasonal dynamics of ground cover in Cirsium arvense – a basis for estimating grazing losses and economic impacts

“…Few would disagree with the definition of a pasture weed proposed 40 years ago by Wells; ‘a species whose presence results in a reduced economic output of a specific system’ (Wells, ). If the decision‐maker is a farm manager, then the specific system is best defined as the farm, as it is only within this framework that the economic consequences of on‐farm decisions can be evaluated (Auld et al ., ). To this end, Auld and co‐authors developed a generic bio‐economic model describing the interactions between weeds, pasture and livestock on a farm and used it to determine the influence of Silybum marianum (L.) Gaertn.…”

“…To this end, Auld and co‐authors developed a generic bio‐economic model describing the interactions between weeds, pasture and livestock on a farm and used it to determine the influence of Silybum marianum (L.) Gaertn. on a hypothetical prime lamb production farm in New South Wales, Australia (Auld et al ., ). Many farm system models have since been developed, aiming to improve the management of commercial farming systems through simulation of alternative farm management strategies (Bryant & Snow, ).…”

“…An important part of this complexity is the dynamic nature of the pasture‐weed system with weed growth (and hence competition for space and resources), pasture growth and quality and grazing animal feed demand (and hence pasture value) varying throughout the year (Auld et al ., ; Bourdôt et al ., ; Chapman et al ., ). The economic consequences of a particular weed on a specific farm (and at a greater scale, such as nationally, when the decision‐maker might, for example, be a research grant manager) will depend on the interplay of these dynamics.…”

“…Many farm system models have since been developed, aiming to improve the management of commercial farming systems through simulation of alternative farm management strategies (Bryant & Snow, ). The effects of weeds (and pests in general) have not yet been included in these models (Bryant & Snow, ), a probable consequence of the complexity of the interaction of weeds with desirable pasture plants and grazing animals (Auld et al ., ; Masters & Sheley, ).…”

Reproductive and vegetative biology ofCirsium vulgare(Savi) Ten. (Compositae: Cynareae)

“…Data reported in Michaux (1984) sugests that this increase will be in the order of a factor of 9 per year on pasture and considerably higher on bare ground. Seeds are certainly not spread uniformly over a wide area, as has been assumed by authors such as Auld et al (1979) when modelling control strategies for fecund annuals and biennials. The rapid spread of this species throughout New Zealand following its introduction is therefore likely to have been aided by humans.…”