A much discussed topic at present is the greenhouse effect on earth. A possible rise in temperature will surely affect butterfly population. It is not absolutely certain to what extent butterfly species will react to a change of climate but a careful prediction can be made by looking at the fluctuation of the species in this century (Atlas of Dutch Butterflies). Seasonal changes have different effects on butterfly populations. Some species will increase while others will decrease. Butterfly species can be divided into six groups, depending on the climate conditions favourable for population increase. When attempting to predict the future situation of certain species, it is important not only to study the climate but also to take into account the biotope and the mobility of the butterflies.