The potential global distribution of Stipa neesiana under current and future climates
Stipa neesiana (Poaceae, EPPO Alert List) is a perennial grass native to temperate South America. It has naturalized in temperate grasslands in New Zealand and Australia where it reduces biodiversity and quality of pastures as it produces unpalatable flower stalks. This plant is as a consequence the object of regulation and management efforts in Australia and New Zealand. S. neesiana has also naturalized in France (including Corsica), Spain (including the Canary Islands), the UK and the USA. Although first recorded in the UK in 1916, France in 1894 and Corsica in 1910, so approximately at the same time as in Australia and New Zealand, it has so far not been recorded as a problematic weed in these northern hemisphere European countries.
As a first step toward a global risk analysis, CLIMEX models of S. neesiana distribution under current climate and under six future climate change scenarios have been undertaken. In North America, the climatically suitable area is relatively extensive, with the model showing that the west coast and coastal south-eastern states of the USA are suitable. High-elevation regions in Central America are also suitable. In Europe, the climatic area suitable for S. neesiana is almost exclusively limited to lands bordering the Mediterranean Sea and inland in the western countries (Belgium, France, Italy, the Netherlands, and Spain). In Asia, the suitable areas are largely confined to high altitude regions along the Himalayas and in the south-eastern regions of China. On the African continent, a large proportion of South Africa, high altitude regions in equatorial countries, coastal regions of Angola and Namibia and northern coastal areas adjacent to the Mediterranean Sea (in Algeria, Libya, Morocco, and Tunisia) are suitable. In Australia, areas with suitable climate are located predominantly in the south-eastern regions, the south-western corner of Western Australia, and in Eastern Queensland. In New Zealand, suitable climate occurs along the eastern side of the South Island and throughout much of the North Island.
When using all the climate change scenarios, the global suitable area for S. neesiana contracted greatly. Most of the contraction occurred in Africa, Asia, North America, South America and Australia and was attributable to increases in temperatures leading to lethal heat stress, which excluded the plant from areas currently designated as subtropical and tropical humid. In Europe, eastward expansion of suitable climate into Germany, Poland, Hungary, Northern Croatia, Serbia, Southern Romania and Northern Bulgaria, and coastal areas along the northern part of the Black Sea is projected under all models. Under all climate change scenarios, South-Western Spain becomes largely unsuitable for S. neesiana.
The actual areas where the species could establish populations would nevertheless be constrained by non-climatic factors such as land-use, as the species grows predominantly in pastures. The future distribution of S. neesiana is therefore likely to be smaller than projected. Pastoral farming nevertheless represents a significant land use in Europe with 65, 33 and 37% of the British Isles, Western and Mediterranean Europe respectively in permanent pasture. A prudent biosecurity strategy would be to prevent the species from spreading from the areas where it is already established.
Sources
Bourdöt G, Lamoureaux SL, Watt MS, Manning L, Kriticos D (2010) The potential global distribution of the invasive weed Nassella neesiana under current and future climates. Biological invasions. DOI:;10.1007/s10530-010-9905-6. http://www.springerlink.com/content/53hn2q843272qu06/