Weed invasions in the Mediterranean with selected examples
A. Uludag1, I.Uremis2 and H. Zengin3
1European Environment Agency, Kongens Nytorv 6, Copenhagen, 1050 Denmark E-mail: ; 2Faculty of Agriculture, MKU, Hatay, Turkey;
3Faculty of Agriculture, Igdir University, Igdir, Turkey
The Mediterranean region has historically faced with introduction of alien species and problems caused by invasive alien species. Many archeophytes, species introduced before the year 1500, are weeds in agricultural areas such as Amaranthus retroflexus and Abutilon theophrasti. The global change, which covers increasing movement of human and goods, changing land use, changing climate inter alia, makes the region more vulnerable to invasions. It is expected that new species that are adapted currently in warmer climateswould adapt in the region and would lead to a modifiedeffects on yield and on control measures.
The well-known example of newly emerged weed species in the Mediterranean is Solanum elaeagnifolium, native to south of North America and Argentina, which has a negative impacts on cropandlivestock production, and on the environment. Its introduction has occurred due to crop seeds, animal manures and bedding movement in different parts of the world. It was introduced to Morocco first in the mid of 20th century and now it is a widely spread weed in all Mediterranean basin. Since theMediterranean climate favours S. elaeagnifolium, which is highly resistantto drought, iteasily spread in semiarid areas. S. elaeagnifolium could become more problematic in the Mediterranean because the climate change projections predict a reduction in rainfall and increasing the frequency of drought years in the region. Furthermore, its northern potential limit would be extended depending on elevation inwinter temperatures.In addition, the reasons for spread could be lack of timely detection and rapid response in the regions where the plant was introduced and distribution pathways were not well controlled.
Infestation of parasitic plants is among the limiting factors of further development in many crops. Orobanche and Phelipanche species (Orobancheaceae) are important pests in vegetable crops, legume crops, tobacco and sunflowers. They could invade larger areas in the Mediterranean countries due to climatic changes as well as the central and northern European countries. Striga species (Orobancheaceae) are mainly native of Africa and infests wide variety of plant species. Striga gesnerioidesinfests crops such as cowpea and tobacco which are traditionally grown in the Mediterranean countries. Three other crops, maize, rice and sorghum, which are produced in the Mediterranean, are attacked by Striga hermontica and Striga asiatica. Studies with ecological niche modelling show that Mediterranean basin is partly suitable for given Striga species. Importing crops infested with Striga seeds might lead to introduction of weeds in Mediterranean countries. Although Striga species need wet conditions and drier climatic conditions are expected in Mediterranean, they might create problem in suitable areas because of their greater ability to adapt to different habitats and agroecosystemsby developing host-specific strains, each capable of attackinga narrow host range. It is a common expectation that the rate of introduction of invasive pests in agriculture will continue to increasein proportion due to globalization, trade and climate change.
There are needs to reveal/understand effect of global change on weed invasions in different scales from individual level to ecosystem level to develop methods and policies for preventing introductions, early detection and fast eradication of newly established/introduced weeds because prevention and early detection are more cost effective than long term containment and control activities.