The common ragweed (Ambrosia atermisiifolia L.) is a plant native to North America which was introduced accidentally to southeastern Europe in the 19th century, and has since become widespread in parts of the continent. Typically growing in urban wasteland and overgrown fields, it is a significant human health risk because many people are allergic to its pollen.
This study by a team in Germany aimed to predict whether the invasive plant was likely to shift its range in Europe due to climate change. To do this, the study tested various models that map the habitats suitable for a species to live in, based on the conditions of temperature and rainfall in the places where it has been observed, and projections for how climate change would affect the locations of suitable habitats (ecological niche models).
To generate the models, the research used GBIF to identify 2,016 records of the ragweed's occurrence in its native North America, and 2,779 records from its invasive range in Europe - together with past climate records and forecasts for climate change based on various scenarios. The accuracy of the models was tested by comparing their results for current suitable habitats with independent data on the regions where ragweed has been reported.
The study found that when only the European occurrences were used, the model produced implausible results. The authors concluded that this was due to sampling bias among the European records available through GBIF when the models were generated (in 2009). While many ragweed records were published from Germany and other parts of northern Europe, few or no records were available from regions where the plant was known to be a problem such as in Italy and Hungary.
However, when the GBIF-mediated data from the plant's native range in North America were used to generate the models, there was a much better match with known occurrences in Europe. On this basis, the researchers predicted that climate change would enable the ragweed to thrive in many more parts of Europe, with potential invasions possible over huge areas including northern France, Germany, the Benelux countries, Czech Republic, Poland, the Baltic States, Belarus and wide parts of Russia.
In view of the high cost of the plant's spread in terms of human health (estimated at €110m per year in Hungary, for example), the authors conclude there is a strong need for control measures to minimize the further spread of common ragweed.
This research has been covered by several German-language news publications, for example in the online version of Die Welt newspaper.
Photo: Common ragweed leaf Meneerke bloem, CC3.0