It has already been established that many animal and plant species are at risk of extinction due to human activity.

Researchers from the University of Sheffield, however, are arguing that conservation efforts are more focused on species on land than in water.

In a study published in the journal Current Biology, Thomas Webb and Beth Mindel looked into comprehensive data on animal conservation available for marine and terrestrial species and found that between 20 and 25 percent of well-known marine species are under threat of extinction, a number that rivals those of animals and plants on land.

According to Webb, there was a general assumption that even though marine environments have been subjected to many harmful human activities that lead to overfishing and pollution, marine species are not in danger of extinction.

"We have shown that, on the face of it, there are indeed far fewer marine species of conservation concern; but much of this can be explained by the fact the conservation status of fewer marine species has been formally assessed," explained Webb, who is from the University of Sheffield's Department of Animal and Plant Sciences.

To declare this means marine species have been examined using criteria released by the International Union for the Conservation of Nature. This is a tedious process, understandably, and it turns out just three percent of species in marine systems out there have been checked at all.

Webb added that when focus is placed on animals and plants that are well-known, estimates involving extinction risk are likelier to be reliable, with discrepancies between marine and terrestrial species disappearing. Whether they came from the sea or not, it is calculated that one out of four species, be it plant or animal, has an increased risk for extinction.

The study is part of a larger program of study that challenges assumptions that divide marine ecology and what is considered "mainstream" ecology. This divide follows the idea that marine ecosystems are fundamentally different from their terrestrial counterparts and thus require a different kind of approach to be researched.

Webb clarifies, though, that marine and terrestrial systems do have inherent differences. However, assumptions have to be examined first as these affect how marine environments are managed, which will affect efforts at addressing extinction in marine animals and plants.

The study received funding support from the Royal Society. Mindel is a PhD student at the university.