In New Caledonia, as in other island environments, invasive plants have impacts on agricultural, environmental and social activities as well. Near 70 plants are considered as noxious in New Caledonia and are found throughout the pacific area (including Australia). More than the half of these species concern cattle grazing systems that are susceptible to biological invasions and an essential component of the Island territory of New Caledonia (11% of the total area). Some of theses weeds threaten some natural ecosystems near the pastoral areas like the dry forests from west cost characterised by a high degree of endemism. Therefore, consideration must be given to the economic, social impacts as well, as the reduction of harm on the environment and territory. The research action `Invasive plants and pasture management" of Agronomic Institute of New Caledonia aims to produce a set of diagnostic tools for better management of pastures in order to improve animal feeding, while conserving the rangeland environment. Concepts and methods of systemic ecology, plant ecology and landscape ecology are used to assess the effects of environmental factors and management practices on botanical compositions in rangeland and grasslands and dry forests. Trial sites have been established to develop methods of invasive weed control and also to obtain information on the biology of species. This paper presents the preliminary results obtained from 2000-2003 about the understanding of invasive processes and their developments for the elaboration of weeds control strategies for the future.