At present, a wide array of factors are detrimentally affecting ocean health, and predicting their combined effects on marine ecosystems remains a difficult challenge.

There exists a mixture of more immediate, short-term, localised threats, such as habitat modification and overfishing, alongside broader, slower changes in underlying global ocean conditions (e.g. water temperature and pH, due to increased atmospheric carbon dioxide). There is concern within the scientific community that the combination fo local/regional/global drivers has the potential to push marine systems to new, and potentially dysfunctional, states.

Individual stressors can affect biological community composition, ecosystem function, and ecosystem  services in significant ways, and much work to date on specific species, or species groups (e.g. corals) provides a compelling body of evidence. Empirical observations of pairwise stressors in combination have, however, shown their effects are not always additive (in which the total effect is the sum of the individual effects). The total effect may be ANTAGONISTIC (total effect < sum of individual effects) or SYNERGISTIC (total effect > sum of individual effects). Incorporating this range of responses in to ecosystem-wide models allows the potential amplifying effects of larger systems both local and global forcings to be explored - this is the reason OSIRIS was created. If synergistic effects prove to have large ecosystem consequences, an additional level of caution may be required in how marine ecosystems are managed and protected. The aim of this work is to provide an analytical framework which allows the effects of multiple simultaneous stressors to be investigated, and the risks to ecosystems to be evaluated.