Global environmental problems do not develop in isolation from each other. There are many interactions, which only seldom exert a dampening influence and much more frequently have an amplifying effect. Linkages are of two types: • Environmental problems can have common

causes. • Environmental problems can influence each other

reciprocally (interfaces). It is not always possible to distinguish interfaces and common causes unequivocally. The distinction is therefore made pragmatically. Common causes represent indirect linkages between environmental problems, while interfaces represent direct relationships (effects). The two types of linkage require different institutional approaches.