Abstract

Nowhere in the world has such a wealth of distribution data been amassed on a country’s wild flora as in the Netherlands. In the course of the 20th century a grand total of about 10 million distribution data were collected on the country’s approx. 1450 wild plant species and filed in two large databases on a grid scale of approx. 1 km2. With these data, which have now been corrected for observer effects to enable more accurate comparison, the floristic changes of the 20th century have been described and quantitatively analysed, using the functional characteristics of species and species groups as a proxy for relevant causative factors.

For the 20th century as a whole, nutrient enrichment (‘eutrophication’) is the single most important cause of changes in the Dutch flora, as reflected in a marked decline in species of nutrient-poor habitats and a marked increase in those of nutrient-rich habitats (see figure). Other key causes are loss of salt-water habitats, acidification and lowering of the water table (‘desiccation’). In the last quarter century, urbanisation and climate change have become the principal driving forces behind the floristic changes observed in the Netherlands. Today, exotic plant species (neophytes) account for a substantial proportion of the Dutch flora, featuring most prominently in environments with a strong human influence.

On the basis of these results a number of conclusions can be drawn of relevance for national environment and conservation policy. In the first place, the study indicates that Dutch environmental policy has failed to control the problem of eutrophication, although it appears to have been more successful in addressing acidification. A second conclusion is that, following a major decline in the first half of the 20th century, certain valuable forms of vegetation, in particular pioneer vegetations of wet, nutrient-poor soils (fens, dune slacks, etc.), now appear to be gradually recovering. The final conclusion of the study is that exotic species are not as yet a threat to the diversity of the indigenous Dutch flora, at least not on a national and regional scale.

Publications

• Tamis, W.L.M., Van ’t Zelfde, M., Van der Meijden, R., &. Udo de Haes, H.A., (in print 2005 Climatic Change). Changes in vascular plant biodiversity in the Netherlands in the 20th century explained by their climatic and other environmental characteristics.
• Tamis, W.L.M., Van ’t Zelfde, M., Van der Meijden, R., Groen, C.L.G. &. Udo de Haes, H.A., 2005, Ecological interpretation of changes in the Dutch flora in the 20th century, Biological Conservation 125: 211-224.
• Tamis, W.L.M., Van der Meijden, R., Udo de Haes, H.A., (submitted), History of non-native vascular plant species in the Netherlands
• Odé, B., Tamis, W.L.M. and Beringen, R., 2004, Beoordelingsmethode Oeverplanten Zoete Rijkswateren. FLORON-rapport 32, BM 04.06: 38 p.
• Tamis, W.L.M., Van der Meijden, R., Runhaar, J., Bekker, R.M., Ozinga, W.A., Odé, B. and Hoste, I., 2004, Standaardlijst van de Nederlandse flora 2003. Gorteria 30 (4/5): 101-195.
• Tamis, W. L. M. & Van 't Zelfde, M., 2003. KilometerhokFrequentieKlassen, een nieuwe zeldzaamheidsschaal voor de Nederlandse flora. Gorteria 29: 57-83.
• Tamis, W. L. M., Van 't Zelfde, M. & Van der Meijden, R., 2003. Effecten van klimaatsverandering op planten in Nederland. Gorteria 29: 93-98.
• Tamis, W.L.M., Van Heeswijk, J., Van ’t Zelfde, M., Van der Meijden, R. & Groen, C.L.G., 2003. Digitale ontsluiting van historische floristische streeplijsten van de provincie Drenthe. Gorteria 29: 157-170.
• Tamis, W.L.M., Odé, B. & Witte, J.P.M., 2003. Possible consequences of the new IUCN regional guidelines for a Red List of vascular plant species in the Netherlands. In: De Iongh, H.H., Bánki, O.S., Bergmans, W., Van der Werff ten Bosch, M.J., 2003. The harmonization of Red Lists for threatened species in Europe. Proceedings of an International Seminar 27 and 28 November 2002, The Netherlands Commission for International Nature Protection, Mededelingen No. 38, Leiden: 181-195.
• Odé, B., Van der Meijden, R. Groen, C.L.G. and Tamis, W.L.M., 2003, Invasieve neofyten in Nederland; een eerste verkenning van hun schadelijkheid. FLORON Leiden, rapport 2003.38: 17 p.
• Tamis, W. L. M., Van 't Zelfde, M. & Van der Meijden, R., 2003. Effecten van klimaatsverandering op hogere planten in Nederland. De Levende Natuur 104: 75-79.
• Tamis, W.L.M., 2005, Nederlandse landschappen veranderen: wat betekent dit voor planten? De Levende Natuur 106 (1): 30
• Tamis,W.L.M., Van 't Zelfde,M. & Van der Meijden,R., 2001. Changes in vascular plant biodiversity in the Netherlands in the 20th century explained by climatic and other environmnetal characteristics. In: Van Oene,H., Ellis,W.N., Heijmans,M.M.P.D., Mauquoy,D., Tamis,W.L.M., Berendse,F., Van Geel,B., Van der Meijden,R., & Ulenberg,S.A. (eds.). Long-term effects of climate change on biodiversity and ecosystem processes. NOP, Bilthoven, blz. 23-51
• Tamis, W.L.M., 2000, Data-analyse van de veranderingen in de Nederlandse flora in de 20e eeuw, Gorteria 26: 247-248.
• Tamis,W.L.M., Van 't Zelfde,M., Van Ek,R. & Witte,J.P.M., 2000. Modellering van de kansrijkdom van het biotisch herstel van natte en vochtige vegetaties. CML 149, CML, Leiden

 

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