From 5 to 7 December 2001 the conference entitled The times they are a-changin'; Climate change, phenological responses and their consequences for biodiversity, agriculture, forestry, and human health was held in Wageningen, the Netherlands. The objective of this conference was to present the latest results of phenological research to demonstrate the importance (added value) of phenological studies to understand better the effects of climate change on ecology, agriculture, forestry and human health. Furthermore, it aimed to strengthen cooperation, networking, and exchange of information among phenologists from different disciplines, meteorologists, and other stakeholders, and to discuss options for better exploitation of existing data and adaptation of phenological observing systems. Over 120 participants from more than 20 countries presented and discussed the latest developments in the field of phenology.
The conference was organized in the context of the European Phenology Network (EPN), which is funded by the Fifth Framework Programme of the European Commission and coordinated by the Environmental Systems Analysis Group of the Wageningen University and Research Center in the Netherlands. The main objective of EPN is to increase efficiency, added value, and use of phenological monitoring and research in Europe in the context of global climate change. EPN was set up after several years of increasing communication between phenologists from all over the world, facilitated by the Commission on Vegetation Dynamics, Climate and Biodiversity (formerly known as the Phenology Study Group) of the International Society of Biometeorology. It was recognized that phenological changes had the potential to contribute to the climate change impact debate because many historic observations exist (gathered by numerous phenological monitoring networks, many of which were still functional). The problem, however, was that there was almost no communication and cooperation between the existing networks. Such cooperation is required in order to develop a large-scale overview of climate change impacts.
This special issue of the International Journal of Climatology includes a selection of papers presented at the conference, which focused on 'observed changes in the timing of life cycle events and assessing the role of climate variables'. In recent years, interest in phenology has increased substantially, caused to a large extent by the publishing of a large number of research articles that demonstrate an observed change in the timing of life cycle events. At the conference, we were able to add to the increasing amount of evidence that the timing of life cycle events of a large number of species is closely linked to climate and, more importantly, that species have responded to the observed increase in temperature. In the last century temperatures increased substantially, and often resulted in new meteorological records. Further, the speed of change has been the highest in at least 1000 years. Concurrently, we see spring starting earlier on dates that would have been extremely rare several decades ago.
The papers of this issue clearly demonstrate that changes in the timing of life cycle events are obvious on different spatial scales (sites to continents), from all over the world, and from a large number of different types of datasets. Sparks and Menzel bring together a number of examples and conclude that the emphasis of phenological analysis is on an advance in spring, which can be linked to an increase in temperature, whereas detection of change in autumn is more difficult to determine, although the general pattern may be towards delay. Ahas et al. show that spring phases have advanced 4 weeks in western and central Europe