The schema described here demonstrates how regional environmental change, involving ecological dynamics such as demographic or landscape transformations on the scale of decades, interact with change on the scale of host-parasite/ pathogen dynamics. How these cross-scale mechanisms produce regional or global scale disease emergence patterns is beyond the realm of conventional epidemiology, or analytical approaches generally. This may explain why such changes either are not apparent or their implications in terms of disease emergence are a low priority to biomedical and public health agencies. Such cross-scale processes are however characteristic of ecosystems, whose dynamics involve interaction of variables and operate on vastly different time and space scales, involving natural processes that are discontinuously distributed as shown in Figure 2 .