There is hardly any other plant than palms which better symbolize a warmer climate. This imagery of palms has now been verified with new scientific facts. Recent climate change allows palms to grow in areas where in the past it was not possible due to too cold winter conditions. This holds true also for some parts of central Europe, where a new world’s northernmost wild palm population can be found, and even further north with the more frequent and successful cultivation of palms in private gardens.

Within the ALARM project amongst others the impacts of climate change are investigated in terms of the composition and distribution of the vegetation. A research team lead by plant ecologist PD Dr. Gian-Reto Walther of the University of Bayreuth discovered a palm species (Trachycarpus fortunei) being among those species profiting from recent climate change. This palm species was introduced from south-east Asia and survived the last few centuries in gardens and parks, but did not succeed to establish in the surrounding area in competition with native species. However, in the last few decades, the species started to spread and regenerate outside the gardens in forests at various sites in the borderline region of southern Switzerland and northern Italy. In these areas a new world’s northernmost wild palm population established in the meantime.

But not only south of the Alps, also the North is experiencing climate change. Further north in central Europe, the palms cultivated in gardens need less protection in winter, respectively survive the winter in western Germany outside without protection. Even in these areas, older individuals started to flower, yield fruits, and in some places seedlings emerge under adult palms. This early stage of rejuvenation in gardens was observed south of the Alps in the early 20th century, but did not implicate the spread in the surrounding forests. For the latter, an additional warming was necessary as seen in the course of the last century. The projected warming for the present century may result also north of the Alps, that the conditions ameliorate for the palms similar to those on the south.

Due to the cold-hardiness of Trachycarpus-palms, they are cultivated in many areas of the world at the range margin of global palm distribution. As a consequence, with one and the same palm species on-going and projected climate change can be monitored across continents: Hence, the palm is an appropriate indicator and appears as a witness of global climate change.

Original publication:
Walther, G.-R.; Gritti, E.S.; Berger, S.; Hickler, T.; Tang, Z. & Sykes, M.T. (2007) Palms tracking climate change. Global Ecology and Biogeography, OnlineEarly article: doi: 10.1111/j.1466-8238.2007.00328.x

Contact address:
PD Dr. Gian-Reto Walther
University of Bayreuth
Department of Plant Ecology
phone: (0921) 55-2575
e-mail: gian-reto.walther@uni-bayreuth.de