Projected Ranges of Invasive Hawkweeds in Australia with Climate Change

Management of invasive species is crucial within conservation reserves in Australia because many species listed under the Threatened Species Conservation Act of 1995 are threatened by invasive species.  Beaumont and his colleagues investigated the projected distributions of three invasive hawkweeds (Hieracium spp.) under current and future climate conditions using ecological niche models (Beaumont et al. 2009).  They found that the hawkweeds still have the potential to increase their ranges under current climate condition but as the climate warms, their ranges are likely to contract overall.  Though the hawkweeds have not established in the Australian Alps, much of the conservation reserves in the Alps are currently climatically suitable for the weeds and they will remain suitable until at least 2070. — Sanami Nakayama 
Beaumont, L.J., Gallagher, R.V., Downey, P.O., Thuiller, W., Leishman, M.R., Hughes, L., 2009.  Modelling the Impact of Hieracium spp. on Protected Areas in Australia Under Future Climates. Ecography 32, 757–764.

 The two main goals of this study were to 1) assess the potential distributions of three hawkweed species Hiernacium pilosella, Hiernacium aurantiacum, and Hiernacium murorum under current and future climate conditions and 2) determine whether the potential ranges of these invasive species coincide with conservation reserves.  The researchers used eight ecological niche models to assess the potential distributions of the hawkweeds under current and future climate conditions in 2030 and 2070.  Ecological niche models are commonly used to generate projections of ranges of exotic species by determining the areas that are likely to remain climatically suitable for a species.  The researchers obtained information about areas that are set aside for conservation in every Australian state and territory, and they used ArcGIS to determine the extent to which the projected distributions of hawkweeds coincide with these reserves. 
Results show that the three hawkweed species have the potential to increase in range and occupy larger areas than those they currently occupy.  The researchers suggest that the weeds have not expanded into areas that are currently climatically suitable for them because they have not had enough time since they were introduced to Australia.  All three species were introduced to Australia less than 20 years ago, and within the next few years, the weeds may realize their invasive potential and expand into larger areas.  The researchers also suggest that the ability of the weeds to expand into suitable areas may be limited by their poor dispersal. 
 As the climate warms, it is projected that the ranges of the hawkweeds will contract overall.  However, about a fifth of the areas that are projected to be currently suitable for the weeds are contained within conservation reserves in the Australian Alps, which are home to many endemic species.  As temperature increases, a larger fraction of suitable areas are projected to be contained within reserves.  The results of this study emphasize the need for control and management of the hawkweeds to minimize the possibility of these species moving into conservation reserves.

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