In 1972, a number of Dutch landscape ecologists united in the Netherlands Society for Landscape Ecology (in Dutch: Werkgemeenschap Landschapsecologisch Onderzoek, WLO). They formed a theory discussion group, aimed at finding a scientific foundation for nature conservation. Scientific here meaning: to be able to predict the future, on the basis of laws like those found in physics and chemistry, in order to elucidate the visible order in nature. After ten yeras the group disbanded without reaching a consensus.This thesis sets out to investigate the background and the spreading of the various ecological theories represented in the WLO. Interviews, publications and archive research have brought to light four separate theories: a vitalistic-holistic,a dynamic, a cybernetic and a chaos theory.